GB2629205A

GB2629205A - Lateral flow test kits

Info

Publication number: GB2629205A
Application number: GB2305898.5A
Authority: GB
Inventors: Uhman Michal; Benjamin Reid Felix; David Milnes Thomas; John Scott Gavin
Original assignee: Gampak Ltd
Current assignee: Gampak Ltd
Priority date: 2023-04-21
Filing date: 2023-04-21
Publication date: 2024-10-23
Also published as: WO2024218501A1; GB202305898D0

Abstract

A lateral flow test kit includes a cassette 2 and a collector 3. The cassette 2 comprises a vial 6 of liquid 54 closed by a seal 22, a test strip 4, a passage 26 leading from the exterior of the cassette 2 to the vial 6 and a conduit 34 communicating between the vial 6 and the test strip 4. The collector 3 can be inserted along the passage 26 to cause a tip 38 of the collector 3 to enter the vial 6 by penetrating or rupturing the seal and release liquid 54, which mixes with an organic sample delivered by the collector 3. The liquid 54 containing the sample passes through the conduit 34 to the test strip 4. A distal end of the passage 26 may be curved to deflect the tip 38 of the collector 3 towards the seal 22 at a more favourable angle. The collector 3 may comprise a receptacle for containing the sample and may be a pipette or cup. The sample may be blood.

Description

TITLE

Lateral flow test kits

DESCRIPTION

Technical field

The invention relates to lateral flow test kits, in which a sample in a liquid medium is applied to a test strip to carry out a chromatographic assay. It specifically relates to test kits in which the sample is obtained from a source on a collection device and needs to be introduced to the liquid medium before being applied to the test strip.

The nature of the test strip itself does not form part of the present invention. It may be conventional or novel and may be used to detect the presence of any desired target such as a virus or other disease-causing agent, a hormone, a toxin, an illegal drug or an environmental contaminant. The source may be a human or animal subject or the collector may be used to collect samples from the environment. Accordingly, the sample may be organic, biological or non-biological and may be in liquid form (e.g. blood) or solid form (e.g.faecal matter).

Background of the invention

Lateral flow tests have been used for a long time, for example in pregnancy tests, but the scale of their use has increased enormously since the Covid-19 pandemic. A typical lateral flow test kit comprises a cassette containing the test strip; a collector for taking a sample from a subject; a vial of liquid medium such as a buffer solution; and an extraction tube, in which the sample from the collector is mixed, and from which a prescribed number of drops of the liquid are then squeezed into a well in the cassette to begin the test. In some known test kits, the vial doubles as the extraction tube.

The large number of components in typical lateral flow test kits requires a fairly complex sequence of steps to be followed to carry out a successful test. The complex sequence of manual steps may also result in a significant proportion of tests being carried out incorrectly, leading to invalid results. Further, the handling of the -2 -components and the transfer of the liquid between them introduce possibilities for contamination of the sample if good practice is not followed while performing the test.

The typical test kits, with multiple steps and components, require a flat, clean surface on which the components can be arranged and successive steps of the test can be carried out, for example to squeeze drops of liquid from the extraction tube into a well. Such a surface might not always be available, especially if a test needs to be conducted outside a domestic setting.

To maintain sterility of the kit before use, each of the components is normally supplied in separate, single-use packaging, which leads to additional waste. Each of the components also needs to be disposed of hygienically after use.

In known test kits, the vial typically has the form of a relatively narrow and deep cone or cylinder, having a depth greater than its width. Because of this shape, such vials must be individually manufactured by injection moulding. Often, a filling operation is integrated into the moulding process, which adds further complexity.

It would be desirable to provide a lateral flow test kit that is improved in one or more of the following ways: * The kit comprises a smaller number of distinct components at the point of use.

* The kit is simpler to use.

* The kit does not require a clear, flat surface on which to conduct a test.

* Tests performed using the kit have a higher proportion of valid results.

* Components of the kit are efficient to manufacture.

Summary of the invention

The invention provides a lateral flow test kit as defined in claim 1.

The invention further provides a method of using a lateral flow test kit as defined in claim 20. -3 -

Features of the invention that are preferred but not essential are defined in the dependent claims.

In accordance with the invention, the vial of liquid is supplied as part of the cassette and remains within the cassette throughout the use of the test kit. The user does not need to remove a seal from the vial or transfer liquid from the vial to an extraction tube. The user also does not need to transfer the liquid from the extraction tube to the cassette. For these reasons, the sequence of steps to be followed by the user is simpler, the risk of error is lower and opportunities for contamination of the sample are avoided. There to are not multiple components to be arranged on a surface and it may be possible to carry out the test while holding the cassette in one hand.

The smaller number of distinct components also results in less packaging, less waste and a simpler process for the supplier to assemble and distribute such test kits. In preferred embodiments of the invention, the collector is retained in the cassette after use, thereby further reducing the number of distinct components that need to be disposed of and decreasing the risk that the sample may come into contact with the environment.

In some embodiments of the invention, the vial comprises a relatively shallow reservoir, having a depth less than its width or length, which is sealed by a planar film or foil. This shape lends itself to manufacture by cheaper methods than injection moulding, for example by flat-bed vacuum-forming an array of the reservoirs, which can then be filled simultaneously and sealed by a single foil sheet of foil before they are separated into discrete units.

In the present specification, terms such as "upper" and "lower" refer to the orientation of the cassette as shown in the drawings. In some embodiments of the invention the orientation may be important once the seal of the vial has been broken, to ensure that the liquid flows in the correct way to reach the test strip. However, test kits according to the present invention are generally less dependent than earlier test kits on being used -4 -in a specific orientation. It is understood that the cassette may be manufactured, stored and distributed in any orientation, at least after the vial has been sealed.

The term "proximal" refers to an end of the cassette through which the collector is inserted and the term "distal" refers to an opposite end of the cassette. The "longitudinal" direction extends between the proximal end and the distal end (in either direction). A "transverse" direction is one that is oblique or perpendicular to the longitudinal direction.

An "oblique" angle to a plane is one that is neither parallel to the plane nor perpendicular to the plane.

Drawings Figure 1 is an exploded, perspective view of a test kit according to the invention.

Figure 2 is a perspective view of the test kit of Figure 1, following assembly and insertion of the collector into the cassette.

Figures 3 to 6 are longitudinal cross-sections through the test kit of Figure 1, showing successive stages in the insertion of the collector into the cassette.

Figure 7 is a partial, perspective, longitudinal cross-section through the distal end of the test kit of Figure 1.

Figure 8 is a perspective, transverse cross-section through the distal end of the test kit of Figure 1.

Figure 9 is a perspective view, from below, of the upper half of the cassette of Figure 1. Figure 10 is a perspective view, from above, of the lower half of the cassette of Figure 1.

Figure 11 is a perspective view, from above, of the cassette of a second embodiment of the invention, with the upper and lower halves separated.

Figure 12 is a perspective view, from above, of the cassette of a third embodiment of the invention, with the upper and lower halves separated.

Figure 13 is a perspective view, from above, of the cassette of a fourth embodiment of the invention, with the upper and lower halves separated.

Figure 14 shows, in a perspective view and in section, the collector of a fifth embodiment of the invention. -5 -

Figure 15 shows, in a perspective view, the collector of a sixth embodiment of the invention.

Detailed description of the drawings

Figures 1 to 10 illustrate a preferred embodiment of a test kit in accordance with the present invention. Figure 1 shows in an exploded view the complete test kit (excluding packaging), which comprises a cassette 2 and a collector 3. Figure 2 shows the test kit of Figure 1 after assembly, with the collector 3 received in the cassette 2.

The cassette 2 is formed by assembling an upper half 8 with a lower half 10 to sandwich a test strip 4 and a vial 6 of a liquid buffer solution between the two halves. The upper and lower halves 8,10 are not intended to be separable by the user and may be clipped, press-fitted, adhered or welded together. The mutually facing surfaces of the upper and lower halves 8,10 may include complementary sealing features 12,14 to reduce leakage of the liquid from the cassette 2 during and after use.

The test strip 4 is securely mounted in a strip chamber 15, which is formed in the lower half 10 of the cassette 2 and closed by the upper half 8 during assembly. The mounting of the test strip 4 will be described in more detail below. It may be a conventional strip used for carrying out a chromatographic assay, typically comprising a strip of absorbent paper on which are deposited one or more transverse lines of a substance that responds to the presence of a target, for example an antigen or reagent that changes colour in the presence of a particular target. A small quantity of liquid containing a sample to be tested is applied near one end of the strip and is transported along the strip by capillary action. Different components of the sample may be transported at different rates and, if a component triggers one of the deposited substances to respond, the colour change of the respective line will be visible through a window 16 in the upper half 8 of the cassette 2. The window 16 may be a simple opening in the upper half 8 or, in order to reduce the risk of leakage from the cassette 2, it may comprise a transparent element attached to the upper half 8 or formed integrally with it. A second, similar window 17 may be provided above a distal end of the test strip 4, through which a user can observe whether the liquid medium has successfully been delivered to the test strip 4, without -6 -waiting for it to be transported along the strip as far as the indicator lines. Alternatively, the entire upper half 8 may be formed from a transparent material so that no distinct window is needed to allow the test strip 4 to be viewed.

In the illustrated embodiment, a label portion 18 on the upper half 8 includes a moulded letter "T" to mark the position of a test line that indicates the presence of a target in the sample; and a moulded letter "C" to mark the position of a control line, which indicates the successful completion of the test by showing that either the liquid itself or a component of it that is expected to be present in any valid sample has reached the position of the control line. The response of a line to the target is not necessarily a change in colour in the visible spectrum. For example, it could be a fluorescence that becomes visible in response to ultra-violet light or it could be the emission of other forms of radiation (e.g. by binding to radioactive particles in the sample) that can be detected with suitable sensors.

The vial 6 comprises a vial reservoir 20 that is closed by a seal 22, which in this embodiment takes the form of a substantially planar film. In the illustrated embodiment, the vial 6 is a discrete component that is received in a vial chamber 24 in the cassette 2. This provides the advantage that the vial 6 may be manufactured and filled with liquid in a first process, then assembled into the cassette 2 in a second process as part of a standard assembly line. Thereby the assembly line does not need to handle uncontained liquids or be restricted to presenting the cassette in an orientation suitable for filling with the liquid. Vials 6 containing different liquids can be used without making any changes to the assembly line. However, it will readily be understood that in alternative embodiments of the invention, the vial chamber 24 itself could serve as the vial reservoir 20, to be filled directly with the liquid then closed by applying a seal 22 across the mouth of the chamber 24. The vial reservoir 20 is somewhat wedge-shaped, being deeper at the distal end than the proximal end, but nowhere having a depth greater than its length. Because of this relatively shallow profile and a planar upper rim that receives the seal 22, the form of the reservoir 20 lends itself to manufacture by vacuum forming. -7 -

The upper and lower halves 8,10 of the cassette 2 respectively define the upper and lower walls of a longitudinal passage 26. A proximal end of the passage 26 has a mouth 28 that opens to the exterior of the cassette 2. The passage 26 is substantially circular in cross-section and extends along a substantially straight portion 29 in the distal direction from the mouth 28. The centreline of the straight portion 29 defines an axis 30, which is generally parallel to the length of the test strip 4. The axis 30 is also parallel to a base of the cassette 2 so that when the cassette rests on a horizontal surface, the straight portion 29 of the passage 26 is orientated horizontally. A distal end of the passage 26 is adjacent to the vial chamber 24. The distal end of the passage 26 is oriented towards the seal 22 of a vial 6 located in the chamber 24, such that the tip 38 of a collector 3 pushed along the passage 26 with sufficient force will be directed to penetrate the seal 22 and enter the vial 6. In the embodiment of the invention illustrated in Figures 1 to 10, the distal end of the passage 26 narrows to a constriction formed by a convex feature 31 then widens and deepens to form a volume 32 adjacent to the vial chamber 24. Within the volume 32, a curved portion 50 of the upper wall of the passage 26 directs the tip 38 of the collector 3 towards the seal 22. A narrow conduit 34 extends transversely from the volume 32 to provide fluid communication between the distal end of the passage 26 and the distal end of the test strip 4.

A collector 3 forms part of the test kit and comprises a shaft 35 with a grip 36 at the proximal end and a tip 38 at the distal end 40. The shaft 35 is able to flex resiliently, at least in a portion towards its distal end 40. The tip 38 of the collector 3 is capable of at least partially entering the vial 6. The illustrated collector 3 is a pipette for delivering a liquid sample into the cassette 2. The shaft 35 of the collector 3 is hollow, forming a receptacle for containing the sample prior to its delivery. The grip 36 comprises a hollow, compressible bulb that is coupled in an airtight manner to the shaft 35, whereby the user can apply pressure to the grip 36 to squeeze the liquid sample out of the shaft 35 via an opening at the tip 38 and can release the pressure on the grip 36 to draw liquid into the shaft 35 through the opening at the tip 38.

The diameters of the shaft 35 and the distal end 40 of the collector 3 are such that they can pass through the passage 26 but the grip 36 has a greater transverse dimension -8 -which forms a shoulder that prevents it from entering the passage mouth 28. The grip 36 may be provided with features such as a concave profile and a knurled texture to make it easier for a user to hold and manipulate the collector 3, both when obtaining a sample and when using the test kit to test the sample. The grip 36 may further be provided with a collar 42, which forms the said shoulder and can be fitted into a recess 44 in the mouth 28 of the passage 26 to close the mouth 28, preferably in a substantially liquid-tight manner. At an intermediate position along the shaft 35, the collector 3 comprises an outward projection 46 in the general shape of a cone tapering towards the tip 38. The outward projection 46 of the collector 3 co-operates with wedge-shaped inward projections 48 at an intermediate position along the passage 26, as will be described below.

Figures 3 to 6 illustrate successive stages in the insertion of a collector 3 into the cassette 2.

In Figure 3, the tip 38 and distal end 40 of the collector 3 of the collector 3 have been inserted through the mouth 28 of the passage 26. The collector 3 initially slides easily along the passage 26, with the outward projection 46 keeping the shaft 35 substantially centred. At an intermediate position of the collector 3 along the passage 26, the outward projection 46 on the shaft 35 wedges against the inward projections 48 formed on the upper and lower halves of the passage 26. The mutual engagement between the inward and outward projections 46,48 resists further movement of the collector 3 in the distal direction so that the user must apply an increased longitudinal force to push the collector 3 past the projections 48. As soon as the mutual engagement of the projections 46,48 has been released, the increased force now being applied by the user causes the movement of the collector 3 to accelerate so that the tip 38 moves towards the distal end of the passage 26 at higher speed.

In Figure 4, the tip 38 of the collector 3 has reached the distal end of the passage 26.

The tip 38 comes into contact with the curved upper wall 50 of the passage and then into contact with the seal 22 of the vial 6.

As shown in Figure 5, when the collector 3 continues to move in the distal direction at the higher speed that results from overcoming the mutual engagement of the projections 46,48, this causes the distal end 40 of the collector 3 to be deflected downwards by the upper wall 50 and causes the tip 38 to pierce the seal 22 of the vial 6.

The shape and rigidity of the tip 38 may be designed to facilitate this piercing. The collector 3 may also be provided with one or more flanges or other projecting elements 39 adjacent to the tip 38, which enhance its penetration of the seal 22 or increase the size of the hole that the penetrating tip 38 creates in the seal 22.

Because of the shape of the vial 6 and the way it is mounted in the vial chamber 24, the substantially planar seal 22 is orientated at an oblique angle to the axis 30 of the straight portion of the passage 26. In some embodiments of the invention, the passage 26 may be straight along its entire length, such that the tip 38 always moves parallel to the axis 30 and penetrates the seal 22 at an oblique angle defined only by the orientation of the seal 22. In the present embodiment, the distal end 40 of the collector 3 is deflected by the curvature of the upper wall 50 at the distal end of the passage 26, which results in the tip 38 penetrating the seal 22 at a steeper -but still oblique -angle defined by the orientation of the distal end of the passage 26 with respect to the plane of the seal 22.

The "orientation of the distal end of the passage 26" means the direction in which the tip 38 is moving through the distal end as it penetrates the seal. The orientation may be defined more precisely by identifying the most distal point on the tip 38 of the collector 3 in its undeflected state; and the plane of the seal 22 prior to contact by the tip 38. The orientation of the distal end of the passage 26 is then defined as the tangent to the path followed by that point, where the path crosses the plane of the seal 22. Any deflection of the tip 38 caused by contact with the seal 22 itself may be ignored so the relevant path is the one that the tip 38 would follow in the absence of a seal.

It has been found that, if the tip 38 approaches the seal 22 at too shallow an angle, it may fail to pierce the seal 22 and instead force its way between the seal 22 and the upper wall 52 of the vial chamber 24. On the other hand, if the tip 38 pierces the seal 22 at too steep an angle or perpendicularly, it can create a neat hole in the seal 22 that -10 -becomes filled by the distal end 40 of the collector 3, thereby preventing liquid 54 from easily flowing out of the vial 6 through the hole. At intermediate, oblique angles, the tip 38 has been found to tear the seal 22 in a way that creates a larger opening, through which the liquid 54 can easily escape.

The seal 22 may be formed with lines of weakness to encourage it to tear in a desired pattern. Alternatively, instead of tearing under pressure from the tip 38 of the collector 3, the seal may be designed to detach from the rim 55 of the vial reservoir 20 so that liquid can escape from the vial 6 over the rim 55. The seal may be a thin, flexible to foil or membrane. It should not be so resilient that it will stretch under pressure from the tip 38, rather than tearing or being pierced. In other embodiments of the invention (not illustrated) the seal 22 of the vial 6 may not be a film but may be a thin, rigid cover. Such a cover will have a defined mode of opening to release the liquid 54 when placed under pressure or impacted by the tip 38 of the collector 3, for example it may be formed with lines of weakness along which the cover can rupture or it may be designed as a sealed flap that can be forced to open about a hinge.

Figure 6 shows the collector 3 inserted into the cassette 2 to its maximum extent. This is determined by the grip 36 abutting the external surface of the cassette 2 around the mouth 28 of the passage 26. More specifically, in the illustrated embodiment, the collar 42 of the grip 36 lodges in the recess 44 in the mouth 28 of the passage 26. Preferably, when the collector 3 is fully inserted into the cassette 2, a substantial length of the distal end 40 of the collector 3 is submerged in the liquid 54. The vial 6 is preferably filled with liquid 54 to a level such that when the cassette 2 is horizontal, the tip 38 of the collector 3 pierces the seal 22 below the surface of the liquid 54. Thereby, the liquid 54 will naturally flow under gravity through the resulting opening into the volume 32. The submerged distal end 40 of the collector 3 will also displace liquid through the opening.

In the illustrated embodiment of the invention, where the collector 3 is a pipette, once the tip 38 of the collector 3 is located in the vial 6, the user squeezes the grip 36 to expel the liquid sample from the collector 3. This causes the sample to mix with the liquid 54 in the vial 6 and also displaces the mixture of liquids from the vial 6 via the opening created in the seal 22. Additionally -and particularly in alternative embodiments of the invention where the collector 3 is not a pipette but contains the sample in a receptacle such as a cup or a loop -the user may manipulate the grip 36 to move the distal end 40 of the collector 3 within the vial 6. This encourages both the transfer of the sample from the collector 3 into the liquid 54 in the vial 6 and also the mixing of the sample with the liquid 54.

As seen in Figure 7, liquid 54 that escapes from the vial 6 will flow over the rim 55 of the vial 6 into a well 56 in the lower half of the volume 32. The conduit 34 is configured to transport the liquid 54 -now containing a fraction of the sample -from the well 56 to the test strip 4. In some embodiments, the conduit 34 may be of small cross section in order that the liquid does not flow freely and flood the test strip 4, its rate of transport through the conduit 34 being controlled by capillary forces. In such cases, the surface texture and/or material of the conduit 34 may be designed -for example, by applying a coating -to ensure that suitable capillary forces exist. In other areas of the test kit, for example where respective surfaces of the upper and lower halves 8,10 are in face-to-face contact, the surface texture and/or material may be selected to reduce capillary forces that might encourage the migration of liquid along the surfaces.

Provided the cassette 2 is generally orientated such that liquid can flow from the vial 6, collect in the well 56 and flow from there towards the test strip 4, successful operation of the test kit is not particularly sensitive to the orientation. Therefore it is suitable for hand-held use, i.e. with the cassette 2 being held in one hand and the collector 3 being inserted using the other hand. Embodiments of the invention that use capillary forces, rather than gravitational flow, to transport the liquid 54 through the conduit 34 may be even less sensitive to orientation.

Withdrawal of the collector 3 from the cassette 2 is limited by the abutment of the outward projection 46 of the collector 3 with the inward projections 48 of the passage 26. Because of the cone shape of the outward projection 46 and the wedge -12 -shape of the inward projections 48, they can pass one another when sufficient force is applied when the collector 3 is moving in the distal direction but they cannot pass one another when the collector 3 is moving in the proximal direction.

In embodiments of the invention where the tip 38 of the collector 3 comprises an enlarged head to accommodate a receptacle such as a cup or loop, then additional liquid may be encouraged to flow from the vial 6 into the well 56 by the user withdrawing the head of the collector 3 from the vial 6. The withdrawing head tends to draw liquid 54 over the rim 55 and into the well 56. The user preferably moves the head into and out of the vial 6 several times, within limits set in the proximal direction by the inward and outward projections 46,48 and in the distal direction by the abutment of the grip 36 against the cassette 2 around the mouth 28 of the passage 26. Each such "piston" action may displace some liquid 54 into the well 56 when the head is pushed into the vial 6 and draw more liquid 54 into the well 56 when the head is pulled out of the vial 6. It also functions to achieve good mixing between the sample and the liquid 54 within the vial, ensuring a homogenous mixture.

When the user has finished transferring the sample, and optionally after they have waited to observe liquid being transported successfully along the test strip 4, they preferably insert the collector 3 to its most distal position so that the collar 42 of the grip 36 fits into the recess 44 in the mouth 28 of the passage 26. This closes the mouth 28 to prevent or reduce the subsequent leakage of liquid 54 from the cassette 2 via the passage 26. In this most distal position of the collector 3, the aforementioned outward projection 46 from the shaft 35 engages with the constriction 31 to create an additional seal that prevents or reduces the flow of liquid from the volume 32 into the straight portion 29 of the passage 26. In other embodiments of the invention, a plug that seals against the constriction 31 at the most distal position of the collector could be provided as a separate feature from the outward projection 46 that resists initial insertion and prevents withdrawal of the collector 3. In other words, the plug and the outward projection 46 could be formed as discrete elements at different positions along the shaft 35. Alternatively, instead of such a plug feature, the shaft 35 could be provided with one or more thin, radial fins 41 (illustrated in Figs. 14 and 15), which can seal around the shaft 35 at any position of the collector 3 along the passage 26, while being able to flex to permit the forward or backward movement of the collector 3 along the passage 26.

After a suitable delay to allow time for the chromatographic assay to be completed, the user can read the result of the test by inspecting the lines of the test strip 4 through the window 16. Then the cassette 2, including the test strip 4, vial 6 and collector 3 can be disposed of safely as a single, sealed unit.

lo Figures 9 and 10 show more detail of the respective opposing faces 60,62 of the upper and lower halves 8,10 of the cassette 2. Although complex in design, each half 8,10 can be formed by injection moulding in a two-part mould from a plastics material such as polypropylene.

It may be seen than the lower sealing feature 14 takes the form of a groove that extends around the passage 26 and the vial chamber 24, while the upper sealing feature 12 takes the form of a complementary rib. The two sealing features 12,14 may be joined to one another in a liquid-tight manner, e.g. by ultrasonic welding or press-fitting, to prevent leakage of liquid from the passage 26 along the interface between the upper and lower halves 8,10, except where permitted by the capillary conduit 34.

The lower cassette half 10 comprises an upstanding boss 68, in which the vial chamber 24 is formed. The boss 68 further provides an inclined, planar seat 70 for the rim 55 of the vial 6, while the upper cassette half 8 provides the inclined, planar upper wall 52 of the vial chamber 24 that clamps the vial 6 in place after assembly.

The strip chamber 15 in the lower cassette half 10 supports the test strip 4 at a low level in the cassette 2, approximately level with the bottom of the well 56. The strip 4 rests on a series of transverse bars 71, which minimize contact with the underlying surface to prevent the longitudinal transfer of liquid by capillary action between the strip 4 and the surface, rather than through the strip itself. The upper cassette half 8 comprises securing bosses 72, which project into the proximal end of the strip chamber 15, -14 -downstream of the window 16, to clamp the test strip 4 in place. The upper cassette half 8 may further comprise at least one metering boss 74, which projects into the strip chamber 15 upstream of the window 16 to exert pressure on the test strip 4 and regulate the rate of transport of liquid from the conduit 34 along it.

Figures 11 to 13 illustrate further examples of test kits that embody the present invention. To the extent that they operate in the same way as the first embodiment, the same reference numerals are used and not all the details will be described again. In each case, the mounting of the test strip 4 in the cassette 2 is substantially the same as in the first embodiment.

Figure 11 illustrates the cassette 2 of a test kit according to a second embodiment of the invention. As in the first embodiment, the cassette 2 is formed by assembling an upper half 8 with a lower half 10. The upper and lower halves 8,10 come together to form a longitudinal passage 26, which extends from a mouth 28 at the exterior of the cassette 2 to a distal end adjacent to a vial chamber 24. A vial 6 contains a liquid buffer solution and is closed by a seal (not illustrated), such as a layer of foil. A strip chamber 15 in the lower half 10 of the cassette extends longitudinally, generally parallel to the passage 26, and comprises transverse bars 71 on which a test strip (not illustrated) may rest. A short conduit 34 provides fluid communication between the distal end of the passage 26 and the strip chamber 15. On assembly of the cassette 2, the upper and lower halves 8,10 may be brought together and mutually attached to secure the vial 6 in the vial chamber 24 and a test strip in the strip chamber 15.

The second embodiment differs from the first embodiment in that the passage 26 is straight along its entire length. The vial 6 comprises a generally conical vial reservoir 20, which is disposed relative to the passage 26 such that when a collector is inserted along the axis 30 of the passage 26, a tip of the collector will enter the vial 6 and contact a wall of the vial reservoir 20 at an oblique angle. Further movement of the collector into the passage 26 will create pressure between the tip of the collector and the vial reservoir 20, causing the path of the tip to be deflected away from the axis 30 as a tip of the collector approaches the distal end of the vial 6. The collector is not -15 -illustrated in Figure 11 but may be similar to the collector 3 of Figure 1 (optionally omitting the outward projection 46). The mouth 28 of the passage 26 may be surrounded by a recess 44, which performs the same function as in the first embodiment.

The vial 6 comprises a rim 55, which assists with locating the vial 6 in the vial chamber 24. The vial rim 55 also provides a planar seat for the seal (not illustrated). The vial 6 may be orientated such that the plane of rim 55 (and hence of the seal) is at an oblique angle relative to the axis 30 of the passage 26. As in the first embodiment, the oblique angle of penetration assists the tip of the collector to form a tear in the seal instead of a neat hole that may be filled by the distal end of the collector and make it more difficult for liquid to flow from the vial 6 into the distal end of the passage 26. The oblique orientation of the vial 6 provides the further advantage of increasing the angle of contact between the tip of the collector and the wall of the vial reservoir 20.

As in the first embodiment, once the seal of the vial 6 has been penetrated, liquid carrying components of the sample can flow from the vial 6 into the distal end of the passage 26.

In this embodiment, when the cassette 2 is horizontal, the conduit 34 is not aligned with the base of the distal end of the passage 26 but is substantially at the level of the axis 30, therefore liquid pooling in the passage 26 is not immediately drawn by gravity into the conduit 34. The user may turn the cassette 2 through roughly 90° about the axis 30 so that the front face 82 visible in Figure 11 is tilted generally downwards. The cassette 2 may be put down with the front face 82 resting on a flat surface or may continue to be held in the hand. This action causes the liquid in the distal end of the passage 26 to flow to the mouth of the conduit 34, from where it is transported through the conduit 34 into the distal end of the strip chamber 15. There the liquid carrying the sample is brought into contact with the test strip for a chromatographic assay to be performed. A window in the upper half 8 of the cassette (not visible in Figure 11) allows the user to see a region of the test strip that comprises lines capable of indicating the outcome of the assay.

-16 -As already noted, the vial 6 illustrated in Figure 11 has a substantially conical shape. This provides it with rotational symmetry, which may make the handling of the vial 6 simpler during its manufacture, filling with liquid and placement in the vial chamber 24. However, it is not essential because the vial 6 does not need to rotate during use of the test kit. Therefore, the vial 6 may have an alternative, non-symmetric shape with a specific internal side wall that is designed to be engaged by the tip of the collector.

Figure 12 illustrates the cassette 2 of a test kit according to a third embodiment of the invention. This design has an advantage that the upper half 8 of the cassette 2 is simple enough to be manufactured by vacuum forming as an alternative to, for example, injection moulding. This embodiment differs from the preceding ones in that the vial 6 is not formed as a discrete component received in a chamber in the cassette 2. Instead, a dome 84 in the upper cassette half 8 serves as the vial reservoir 20. In a preliminary process, with the upper cassette half 8 held in an inverted orientation compared with Figure 12, the vial 6 will be filled with the desired volume of liquid, then the mouth of the vial 6 may be closed by a planar seal (not visible in Figure 12). As in the first embodiment, a passage 26 is formed between the upper and lower cassette halves 8,10. It extends longitudinally from an external mouth 28, initially along a straight portion 29, to reach a distal end that curves upwards and away from the axis 30 of the straight portion 29 towards the seal of the vial 6. In this embodiment, the plane of the seal is substantially parallel to the axis 30 so the distal end of the collector (not illustrated) needs to be quite flexible in order for its tip to follow the curved wall 50 of the passage and approach the seal at a sufficiently steep angle to penetrate it.

Once the seal has been breached, liquid will flow out of the vial 6 and fall into a collection chamber 86 formed in the lower cassette half 10, which surrounds the distal end of the passage. Some of the released liquid may also fall into the distal end of the passage itself When sufficient liquid -now mixed with the sample from the collector -has accumulated in the collection chamber 86, the user may turn the cassette 2 through roughly 90° about the axis 30 so that the rear face 87 indicated in Figure 12 is tilted generally downwards. This causes any liquid that has fallen into the distal end of the passage to drain through an opening 88 into the collection chamber 86. At the same -17 -time, the liquid in the collection chamber 86 flows to the mouth of the conduit 34, from where it is transported through the conduit 34 into the distal end of the strip chamber 15, to be applied to the distal end of a test strip (not illustrated) as previously described.

Figure 13 illustrates the cassette 2 of a test kit according to a fourth embodiment of the invention. Its most significant difference from the preceding embodiments is that, when the cassette 2 rests on a horizontal surface, the test strip in the strip chamber 15 extends longitudinally and horizontally as before but the collector is inserted through a passage 26 that extends vertically through a boss 90 from an external mouth 28 to a distal end adjacent to a vial 6. As in the third embodiment, the vial 6 is not formed as a discrete component received in a chamber in the cassette 2. Instead, a generally semicircular recess 92 in the lower cassette half 10 serves as the vial reservoir 20 and its upper side may be closed by a planar seal (not shown) seated on the upper face 62 of the lower half 10. The passage 26 is aligned with a curved internal wall of the vial 6 so that, as a collector (not shown) is inserted along the passage 26, the tip of the collector makes contact with the curved wall and is deflected around the curve. The user may then turn the cassette 2 about its longitudinal axis so that the rear face 87 indicated in Figure 13 is tilted generally downwards. This causes liquid to drain from the vial 6 into the distal end of the passage and to accumulate in a collection chamber 86, which in the illustrated embodiment is in the form of a cylinder lying parallel to the strip chamber 15.

A narrow conduit 34 provides fluid communication between the collection chamber 86 and the strip chamber 15, through which the liquid is transported at a controlled rate, to be applied to the distal end of a test strip (not illustrated) as previously described.

The vertical passage 26 in the fourth embodiment means that when a collector is inserted along the passage 26 it approaches the vial seal 22 at a steep angle, making it more certain that the tip of the collector will pierce the seal 22 rather than deflecting off it. It is not essential that the passage 26 should be perpendicular to the plane of the seal 22: it can easily be envisaged that it could be inclined so that the collector approaches the seal 22 at an oblique angle, though this might require the upper half 8 to be formed in a more complex mould. A disadvantage of this embodiment is that the vertically extending boss 90 makes the cassette 2 less compact than the preceding ones.

-18 -The passage 26 may be made shorter but then, after use of the test kit, the proximal end of the collector will be left protruding from it. The collector may be removed for separate disposal but it is preferred to retain its distal end, still carrying a residue of the sample, inside the cassette after use. Therefore the collector may be provided with a weak point (not illustrated) at a suitable position along its length, which makes it easy to snap off the proximal end of the collector after use, leaving the distal end in the cassette 2. The boss 90 may be provided with a notch 94 intersecting the mouth 28 of the passage 26, in which the shaft of the collector can be lodged adjacent to its weak point to facilitate snapping the collector into two pieces. It should be noted that this feature will principally be applicable to embodiments of the invention where the collector comprises a receptacle at its distal end for containing the sample, rather than being a pipette comprising a hollow shaft.

Each of the illustrated embodiments of the cassette 2 according to the invention comprises a single test strip 4. However, it can easily be envisaged that a single cassette 2 could comprise two or more test strips 4, each used for detecting the presence of a different substance in the sample (or for detecting the same substance as a way of verifying the validity of the result of the test). It will generally be convenient for the multiple test strips 4 to be arranged in parallel. They may be disposed on one side or on both sides of the passage 26. Liquid containing the sample may be delivered from the vial 6 to more than one test strip 4 via a common conduit 34. Alternatively, each test strip 4 may be supplied by a separate conduit 34.

Figure 14 illustrates an alternative collector 3 that may be used with a cassette 2 substantially as illustrated in any of the first to fourth embodiments of the invention.

This collector 3 is not a pipette; instead its receptacle for containing the sample is a cup 96 at the distal end 40. Such a cup 96 may contain a small quantity of blood or another biological or organic liquid. It may also contain a solid or semi-solid sample. In this embodiment, no fluid communication is required between the proximal and distal ends of the collector 3 so the shaft 35 may be solid (but a hollow shaft is not excluded). A set of flexible, radial fins 41 about the shaft 35 provide a seal between the shaft and the passage 26 as the collector is manipulated to move forwards and -19 -backwards in the passage 26. This helps to contain the liquid from the vial 6 and the potentially hazardous sample within the cassette 2 during and after use of the test kit.

Figure 15 illustrates a further alternative collector 3, which is similar to that in Figure 14, except that the receptacle for the sample comprises one or more loops 98.

Each loop 98 is suitable for holding a drop of blood or another liquid sample, which is kept in place by surface tension. This illustrates that a receptacle suitable for use in a collector 3 according to the invention does not need to enclose the sample fully or even substantially in order to perform its functions of containing the sample and delivering to it into the vial 6.

Claims

-20 -CLAIMS1. A lateral flow test kit comprising a cassette and a collector, wherein: the cassette comprises: a vial of liquid; a test strip; a passage having a proximal end open to an exterior of the cassette and a distal end adjacent to the vial; and a conduit having an inlet in communication with the distal end of the passage and an outlet adjacent to the test strip; the vial comprises a seal for retaining the liquid in the vial; the distal end of the passage is oriented towards the seal; the collector comprises a distal end for delivering a sample to be tested; and the cassette and the collector are configured such that the collector can be inserted along the passage to cause the distal end of the collector to penetrate the seal and enter the vial, thereby allowing the collector to deliver the sample into the liquid and allowing liquid from the vial to flow into the distal end of the passage, from where the liquid may be transported through the conduit to the test strip.
2. A kit according to claim I, wherein the seal is generally planar and the orientation of the distal end of the passage is at an oblique angle with respect to the plane of the seal.
3. A kit according to claim 2, wherein the passage comprises a substantially straight portion that defines an axis, and wherein the distal end of the passage is curved or inclined with respect to the axis.
4. A kit according to claim 2, wherein the passage comprises a substantially straight portion that defines an axis, and wherein the plane of the seal is at an oblique angle with respect to the axis.
-21 - 5. A kit according to claim 3 or claim 4, wherein the test strip is substantially parallel to the axis of the passage.
6. A kit according to any preceding claim, comprising at least one further test strip, which is in fluid communication with the distal end of the passage via the said conduit or via a further conduit.
7. A kit according to any preceding claim, wherein the cassette further comprises a well, which is open to the distal end of the passage for receiving liquid released from the vial; and wherein the inlet of the conduit opens into the well.
8. A kit according to claim 7, wherein the passage comprises a constriction proximally of the well and wherein the collector comprises a plug for engagement with the convex feature of the passage to resist the flow of liquid from the well in a proximal direction along the passage.
9. A kit according to claim 7 or claim 8, wherein the well is configured to collect liquid from the vial in a first orientation of the cassette and to deliver the liquid into the conduit in a second orientation of the cassette.
10. A kit according to any preceding claim, wherein the conduit is a capillary tube.
11. A kit according to any preceding claim, wherein the passage and the collector comprise mutually engaging structures that resist distal movement of the collector past an intermediate position along the passage.
12. A kit according to claim 11, wherein the mutually engaging structures comprise at least one inward projection on the passage and at least one outward projection on the collector.
13. A kit according to claim 11 or claim 12, wherein the mutually engaging structures are shaped to prevent the collector being withdrawn fully from the passage.
-22 - 14. A kit according to any preceding claim, wherein the collector comprises a shoulder that is too wide to enter a mouth of the passage, the shoulder forming a liquid-tight seal around the mouth when the collector is fully inserted into the passage.
A kit according to any preceding claim, wherein the vial is a discrete component received in a chamber in the cassette.
16. A kit according to any preceding claim, wherein the collector comprises a receptacle for containing the sample prior to its delivery.
17. A kit according to claim 16, wherein the receptacle is a cup or a loop.
18. A kit according to claim 16, wherein the collector is a pipette, which comprises means at a proximal end of the collector for expelling the sample from the distal end of the collector.
19. A kit according to claim 18, wherein the means for expelling the sample comprises a compressible bulb in fluid communication with the distal end of the collector.
20. A method of using a lateral flow test kit that comprises a cassette and a collector; wherein: the cassette comprises: a vial of liquid; a test strip; a passage having a proximal end open to an exterior of the cassette and a distal end adjacent to the vial; and a conduit having an inlet in communication with the distal end of the passage and an outlet adjacent to the test strip; the vial comprises a seal for retaining the liquid in the vial; -23 -the distal end of the passage is oriented towards the seal; and the collector comprises a distal end for carrying a sample to be tested; the method comprising inserting the collector along the passage towards to cause the distal end of the collector to penetrate the seal and enter the vial, thereby allowing the collector to deliver the sample into the liquid and allowing liquid from the vial to flow into the distal end of the passage, from where the liquid may be transported through the conduit to the test strip.
21 A method according to claim 20, wherein the seal is generally planar and wherein the distal end of the collector enters the vial at an oblique angle to the seal.
22. A method according to claim 20 or claim 21, wherein the step of inserting the collector involves applying a predetermined force sufficient to overcome a resistance offered by mutually engaging structures of the passage and the collector, the predetermined force also being sufficient for the tip of the collector to penetrate the seal of the vial.
23. A method according to any of claims 20 to 22, wherein the step of inserting the collector comprises moving the tip of the collector through a substantially straight portion of the passage that defines an axis, then moving the tip of the collector through the distal end of the passage, which is inclined with respect to the axis to deflect the tip towards the seal.
24. A method according to any of claims 20 to 23, comprising the further step of withdrawing the distal end of the collector from the vial to draw liquid out of the vial.
25. A method according to any of claims 20 to 24, wherein, in a first orientation of the cassette, liquid released from the vial collects in a well open to the distal end of the passage; the method comprising the further step of turning the cassette to adopt a second orientation, in which the liquid is delivered from the well into the conduit.
-24 - 26. A method according to any of claims 20 to 25, wherein the collector is a pipette, the method further comprising operating means at a proximal end of the collector to expel the sample from the distal end of the collector into the vial.
27. A method according to claim 26, wherein the step of expelling the sample comprises compressing a bulb at the proximal end of the collector.