WO1994004272A1

WO1994004272A1 - Fluid testing device

Info

Publication number: WO1994004272A1
Application number: PCT/GB1993/001797
Authority: WO
Inventors: Peter Alan Neill; Thomas Lydford
Original assignee: Hypoguard (Uk) Limited
Priority date: 1992-08-26
Filing date: 1993-08-24
Publication date: 1994-03-03
Also published as: AU4968693A; GB9218118D0

Abstract

The present invention relates to a device for assessing a fluid sample, which device comprises: a) a fluid receptor means (2) adapted to receive a sample of a fluid from an external source; b) a substantially closed chamber (5) adapted to receive fluid from the receptor means; c) a member (9) providing at least part of one wall of said chamber, said member (9) carrying one or more reagents adapted to respond to one or more components of the fluid sample and adapted to give an indication of that response which can be detected from the exterior of the chamber (5); d) a bore (3) connecting the fluid receptor means (2) and the chamber (5), which bore (3) has an outlet (15) at said chamber (5) end of the bore the diameter of the outlet bore being selected such that the fluid in the bore is adapted to form a droplet or meniscus at the outlet (15) to the bore which droplet or meniscus is adapted to contact the reagent carrying member whereby the bore (3) is adapted to conduct the fluid from the receptor means (2) to the chamber (5) and to deposit the fluid onto a pre-determined area of the said reagent carrying member (9); which device is characterised in that at least the exposed rim of the sample receptor means is modified so as to reduce the surface tension effects thereof with respect to the fluid to be assessed and/or the receptor means is provided with means (4, 4a) to allow air to flow to and from the space above the meniscus of fluid within the receptor means (2).

Description

FLUID TESTING DEVICE

The present invention relates to a device, notably to a sample collecting device.

BACKGROUND TO THE INVENTION;

In our co-pending International Application Publication No WO 92/07655 we have described and claimed an integral fluid sample collector and sample assessment device, which comprises: a. a fluid receptor means adapted to receive a sample of a fluid from an external source; b. a substantially closed chamber adapted to receive fluid from the receptor means; c. a member providing at least part of one wall of said chamber, said member carrying one or more reagents adapted to respond to one or more components of the fluid sample and adapted to give an indication of that response which can be detected from the exterior of the chamber; which device is characterised in that it also comprises: d. a bore connecting the fluid receptor means and the chamber, which bore has an outlet at said chamber end of the bore; and in that the diameter of the outlet is selected such that the fluid in the bore is adapted to form a droplet or meniscus at the outlet to the bore which droplet or meniscus is adapted to contact the reagent carrying member whereby the bore is adapted to conduct the fluid from the receptor to the chamber and to deposit the fluid onto a pre-determined area of the said reagent carrying member.

Preferably, the chamber has means to vent or accommodate air displaced by the fluid entering the chamber.

Preferably, the device is in the form of a machined or moulded metal, glass or plastic unitary construction body member comprising a cup or recess having an exposed open top into which the sample to be tested is placed. The cup or recess is connected by a bore to a chamber within the body which has one face thereof formed at least in part from a demountable generally planar member. This member carries the reagent for the test to be carried out on or accessible from one face thereof and is adapted to provide a visual display of the response from the reagent to the sample at the other face thereof. The invention is not however limited to visual display of the response. It may be possible for the response to be detected as a response outside the visible spectrum, for example in the infra-red or ultra-violet spectrum.

We have found that in some cases a blood sample applied to the sample collecting recess or cup of such a device did not appear to wet the member carrying the reagent composition, usually a membrane wall of the chamber opposite to the outlet of the capillary bore connection between the chamber and the sample collecting cup or recess. This was considered to be because the droplet formed at the outlet to the capillary bore did not readily detach from the outlet of the bore to fall onto or flow into contact with the membrane forming the opposed wall. Various attempts were made to assist detachment of the droplet from the bore outlet, for example by tapping the device or by configuring the chamber so that the droplet wetted the side walls of the chamber and was drawn by surface tension effects onto the membrane wall.

However, we have now found that the problem is not solely located at the outlet end of the bore, but is caused also by the surface tension effects at the rim of the collection cup or recess. These effects act to retain the fluid droplet in the cup or recess and do not allow it to detach from the rim and flow through the bore into the chamber. If the cup or recess is modified to reduce the surface tension effects, the fluid within the cup or recess more readily flows through the capillary bore and wets the membrane wall of the chamber. SUMMARY OF THE INVENTION:

Accordingly, the present invention provides a device for assessing a fluid sample, which device comprises: a. a fluid receptor means adapted to receive a sample of a fluid from an external source; b. a substantially closed chamber adapted to receive fluid from the receptor means; c. a member providing at least part of one wall of said chamber, said member carrying one or more reagents adapted to respond to one or more components of the fluid sample and adapted to give an indication of that response which can be detected from the exterior of the chamber; d. a bore connecting the fluid receptor means and the chamber, which bore has an outlet at said chamber end of the bore whereby the bore is adapted to conduct the fluid from the receptor means to the chamber and to deposit the fluid onto the said reagent carrying member; which device is characterised in that at least the exposed rim of the sample receptor means is shaped so as to reduce the surface tension effects thereof with respect to the fluid to be assessed and/or the receptor means is provided with means to allow air to flow to and from the space above the fluid within the receptor means.

The receptor means is preferably a cup or recess having an open end having a circumferential rim. Typically, a user places his finger carrying blood from a pin prick or other skin puncture in contact with the rim. The user transfers the blood from the finger into the cup or recess by wiping the finger across the rim. Whilst the surface tension properties of the rim can be decreased by forming the rim from or coating the rim with a material which is not readily wet by the blood, this may present problems in manufacturing the device. It is therefore preferred to modify the construction of the rim so that its surface tension effects are reduced mechanically. This can be achieved by forming the rim with discontinuities in its perimeter which serve to break the meniscus of the blood or other fluid in the receptor means at one or more points around the rim of the cup or recess.

Alternatively, air can be introduced into the cup above the surface of the fluid at or below the rim, for example by means of a vent hole through the wall of the device. This will allow air to flow into the cup or recess to break any vacuum which is drawn between the top surface of the fluid and the finger across the top of the cup or recess. This will allow the fluid to drain more readily from the cup or recess through the bore leading to the chamber of the device.

The discontinuities in the rim of the cup or recess may take a wide range of forms, for example a toothed or crenellated configuration to the rim. The pitch of the teeth or crenellations are larger than can be spanned by the fluid under surface tension forces so that the fluid readily detaches from the rim, thus allowing the fluid in the cup or recess to flow into the bore leading to the chamber. Alternatively, the discontinuities can be provided by the crests and troughs of a fluted or ribbed interior surface to the cup or recess which give a saw tooth rim to the cup or recess where the interior surface of the cup or recess intersects with the surface of the body of the device. It will be appreciated that the projections may be axial as with a crenellated rim, or may be radial as when a fluted cup interior surface intersects with a flush surface of the body of the device. Furthermore, the crenellations or saw tooth formations may project into the body of the device rather than project from it, as for example when radial saw cuts are made across the face of the device in whose plane the open end of the cup or recess lies.

However, it is preferred to form the rim with a plurality of upstanding axial projections which serve to raise the user's finger out of direct contact with the rim and to break any meniscus which attempts to form at the rim of the cup or recess. Such projections can be integrally formed during moulding of the main body of the device or can be in the form of short rods which are set into the rim or into the body of the device around the rim of the cup or recess during moulding of the body of the device.

The projections conveniently take the form of short cylindrical rods or studs having rounded exposed tips set into the body of the device adjacent the rim or into the rim of the cup or recess itself. The projections are preferably from 0.5 to 5, typically from 1 to 2.5, mms long so as to keep the users skin clear of the surface of the rim at at least two places around the periphery of the rim. Preferably, the projections are located symmetrically around the perimeter of the rim, for example at from 15 to 120° intervals.

Where discontinuities in the rim of the cup or recess are present, these also serve the function of allowing air to flow in and out of the space above the fluid meniscus in the cup or recess. This allows the fluid to drain from the cup or recess into the underlying chamber without the formation of a vacuum between the user's finger and the fluid. This venting also has the effect of minimising any pumping effect on the flow of fluid into the chamber when the user varies the pressure he applies in retaining his finger in place upon the rim of the cup or recess. Furthermore, the venting reduces the risk of aeration of the blood sample which may occur when such pumping occurs. Aeration of the sample may lead to inaccurate test results.

The admission of air into the space above the fluid in the receptor means may also be achieved by providing one or more vent passages through the side wall of the cup or recess and/or by forming the body of the device surrounding the cup or recess from a foraminous or porous material, for example from a fritted ceramic. However, it is preferred to form the rim of the cup or recess with discontinuities as described above which will achieve the venting effect.

As indicated above, the receptor means communicates with the underlying chamber of the device by means of a bore. This can be a conventional circular cross-section bore. However, it may be desired to form the bore with a non-uniform cross-section so as to minimise flow restriction due to surface tension effects. Thus, the bore may have a squared, triangular, cruciform or stellate cross-section, which may be formed during moulding of the device or by subsequent machining. It is also preferred to give the interior face of the receptor means, for example the cup or recess, and the bore a sand or bead blasted finish using conventional techniques to further reduce surface tension effects.

It may also be desirable to modify the outlet at the chamber end of the bore between the receptor means and the chamber so that the fluid more readily detaches from the outlet. This can be achieved in a similar manner to the modification of the rim of the cup or recess. For example, the bore can be of a squared, cruciform or stellate cross-section so as to provide a number of sharp turns in the outlet rim which serve to break the meniscus which forms at the outlet to the bore. Alternatively, the rim can be formed as a sharp rim so as to minimise the contact area between the fluid and the outlet rim.

Apart from the provision of the projections or other means for modifying the surface tension effects at the rim of the* receptor means, and optionally at the chamber end of the bore between the receptor means and the chamber, the device can be essentially identical to that described in our co-pending International Application.

DESCRIPTION OF THE DRAWINGS:

A preferred form of the device of the invention will be described by way of illustration only with respect to the accompanying drawings in which Figure 1 is an axial cross- section through the device; and Figure 2 is an exploded perspective view of an alternative form of the device of Figure

1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

The device of Figure 1 comprises a cylindrical housing member

1 which can be injection moulded from a suitable plastic, for example a polystyrene; or machined from a metal, such as brass or a stainless steel, or from a fritted ceramic or from glass. At one end, the housing is formed with a sample receiving cup

2 connected to an axial capillary bore 3. The cup 2 has a rim which carries a number of upstanding axial projections 4 about

2 mms long which are moulded integrally with the rim of the cup during moulding of the cup. Alternatively, when the cup is machined from solid material, the projections 4 can be lengths of rod inserted into the cup rim. The projections 4 serve to prevent the formation of a continuous contact between the rim and the user's finger as a user draws his fingertip across the open mouth of the cup 2 so as to transfer a drop of blood into the cup 2. A bore 3 connects the base of the cup 2 with a chamber 5 formed in a base of the device. Typically, the bore

3 has a diameter of from 0.25 to 2.5 mms and the chamber has an axial depth of from 0.5 to 5 mms. The bottom end of the bore terminates in a tapered edge 15 which helps the blood to pass from the bore into the chamber 5.

The base 11 is a second plastics moulding which has a floor 13 and side walls 14 and into which the housing 1 can be fitted, to form the chamber 5. The floor 13 has an aperture 12. A reagent pad 9 is mounted in the chamber 5 so that it extends across the aperture 12 and is clamped in place by the action of push-fitting the housing 1 into the base. The chamber 5 is vented to the atmosphere by a labyrinthine vent passage indicated at 8. Preferably, the housing 1 and the base 11 are formed symmetrically about the longitudinal axis of the housing .

The reagent pad 9 can be in the form of a disc coated with a reagent on one face, or the reagent can be impregnated into the material of the disc.

In the alternative form of the device shown in Figure 2 the internal face of the cup 2 is fluted or carries radial ribs on its surface which extend to the rim. By virtue of the fact that the interior of the cup is a cone shape, the ribs or flutes form a saw toothed rim to the cup having a series of axial projections 4a as shown in Figure 2. It may be desired to blunten the crowns of the saw teeth to minimise the risk of injury to a user.

In use, a user wipes his finger across the rim of cup 2 to transfer a drop of blood into the cup. Due to the projections 4 or 4a on the rim, a continuous circle of contact between the blood and the rim of the cup 2 is not formed. As a result, surface tension effects at the rim do not retain the droplet of blood and the blood readily travels along the bore 3 due to capillary action and/or under the influence of gravity to form a droplet at the outlet end of bore 3, as shown dotted in Figure 1. Since the surface tension effects of the rim are no longer present to a major extent, the drop can readily detach from the outlet of bore 3 to fall onto the reagent pad 9 without the need to tap or "flick" the device, as might have been required where the rim does not carry the projections 4.

The blood sample is contained within chamber 5 and there is little risk of escape of the blood to contaminate the user, other samples or any test machine in which the response of the reagent is assessed. The reagent responds to one or more of the components in the blood in the usual manner and this response can then be observed through the circular viewing aperture 12 from outside the container. Again, this response can be viewed without the need to remove the blood from chamber 5, further reducing the risk of cross-contamination.

Once the response has been generated, it can be observed and the device then discarded. Since the device is of known size and shape, and the dimensions and the location of the viewing aperture in the base 11 are accurately known, the device can readily be mounted in a suitable receptacle in a response monitoring device so that the outer face of disc 9 can be observed. The device can thus readily be handled mechanically where large numbers of samples are to be processed, or the device can be readily handled by a blind or infirm person to locate it in a monitoring device.

The invention thus also provides a method for testing a fluid sample for the presence of a component or property therein, which method is characterised in that the sample of fluid is applied to the receptor of a device of the invention, the fluid is allowed to flow through the bore to the chamber and to contact the reagent(s) carried by the wall thereof; and the response of the reagent(s) to the fluid is observed externally through the wall of the chamber.

Claims

CLAIMS :

1. A device for assessing a fluid sample, which device comprises: a. a fluid receptor means adapted to receive a sample of a fluid from an external source; b. a substantially closed chamber adapted to receive fluid from the receptor means; c. a member providing at least part of one wall of said chamber, said member carrying one or more reagents adapted to respond to one or more components of the fluid sample and adapted to give an indication of that response which can be detected from the exterior of the chamber; d. a bore connecting the fluid receptor means and the chamber, which bore has an outlet at said chamber end of the bore whereby the bore is adapted to conduct the fluid from the receptor means to the chamber and to deposit the fluid onto the said reagent carrying member; which device is characterised in that at least the exposed rim of the sample receptor means is shaped so as to reduce the surface tension effects thereof with respect to the fluid to be assessed and/or the receptor means is provided with means to allow air to flow to and from the space above the fluid within the receptor means.

2. A device as claimed in claim 2, characterised in that the rim of the receptor means is formed from or is coated with a material which is not readily wet by the fluid to be assessed.

3. A device as claimed in claim 1, characterised in that the rim of the receptor means is provided with a plurality of discontinuities in its perimeter.

4. A device as claimed in claim 3, characterised in that the discontinuities are provided by axial and/or radial projections on the rim of the receptor means.

5. A device as claimed in claim 1, wherein the rim of the receptor means is provided with a plurality of upstanding axial projections which are adapted to raise a user's fingertip out of contact with the rim at at least two positions around the circumference of the rim and to allow air to flow into the space above the fluid in the receptor means so as to prevent the formation of a vacuum between the surface of the fluid and the user's finger tip.

6. A device as claimed in either of claims 4 and 5, characterised in that the projections have a length of from 0.5 to 5 mms.

7. A device as claimed in any one of claims 3 to 6, characterised in that the discontinuities in the rim are located at intervals of from 15 to 120° around the perimeter of the rim.

8. A device as claimed in any one of the preceding claims, characterised in that it is of a generally radially symmetrical form having the fluid receptor located at one end thereof and the chamber at the other end thereof and having an axial bore for fluid flow connection between the chamber and the receptor and in that the rim of the receptor means is provided with a plurality of axial projections.

9. A device as claimed in any preceding claim, characterised in that the end of the axial bore nearest the chamber ends in an outwardly tapered sharp edge.

10. A device as claimed in any one of the preceding claims, characterised in that air passages are formed in the side wall of the receptor means which are adapted in use to allow air to flow into the receptor means and to prevent the formation of a vacuum between the user's finger tip and the surface of the fluid in the receptor means.

11. A device as claimed in Claim 10, characterised in that the receptor means is formed at least in part from a porous or foraminous material and the air passages are provided by the pores in the material.

12. A device as claimed in any one of the preceding claims, characterised in that the interior surface of the receptor means and/or of the bore is sand or bead blasted.

13. A device as claimed in any one of the preceding claims, characterised in that the bore has a diameter of from 0.25 to 2.5 mms and the chamber has an axial depth of from 0.5 to 5 mms.

14. A device as claimed in any one of the preceding claims, characterised in that the receptor means is a receptor means in a device as described and claims in PCT Application No WO 92/07655.

15. A device as claimed in claim 1, substantially as hereinbefore described with respect to and as shown in any one of the accompanying drawings.

16. A method for testing a fluid sample for the presence of a component or property therein, which method is characterised in that the sample of fluid is applied to the receptor of a device of claim 1, the fluid is allowed to flow through the bore to the chamber and to contact the reagent(s) carried by the wall thereof; and the response of the reagent(s) to the fluid is observed externally through the wall of the chamber.

17. A method as claimed in claim 16, characterised in that the fluid is blood and the reagent(s) give a colour response to the glucose content of the sample.