HAEMOGLOBIN TEST KIT

A haemoglobin test kit comprising: a lateral flow test strip having a sample collection portion, a conjugate portion and a plurality of test lines downstream of the conjugate portion, the conjugate portion comprising haemoglobin antibody conjugated with coloured particles to bind with haemoglobin in a sample fluid; wherein each test line comprises a different concentration of haemoglobin antibody, and wherein each test line comprises a particular concentration of haemoglobin antibody tuned to bind with haemoglobin in the sample fluid.

FIELD OF THE INVENTION

This invention relates to a haemoglobin test kit.

BACKGROUND OF THE INVENTION

In diabetes management, as stated in “Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus”—an Abbreviated Report of a WHO (World Health Organization) Consultation, “HbA1c reflects average plasma glucose over the previous eight to 12 weeks. It can be performed at any time of the day and does not require any special preparation such as fasting. These properties have made it the preferred test for assessing glycaemic control in people with diabetes. More recently, there has been substantial interest in using it as a diagnostic test for diabetes and as a screening test for persons at high risk of diabetes. Owing in large part to the inconvenience of measuring fasting plasma glucose levels or performing an OGTT (oral glucose tolerance test), and day-to-day variability in glucose, an alternative to glucose measurements for the diagnosis of diabetes has long been sought. HbA1c has now been recommended by an International Committee and by the ADA (American Diabetes Association) as a means to diagnose diabetes. Although it gives equal or almost equal sensitivity and specificity to a fasting or post-load glucose measurement as a predictor of prevalent retinopathy, it is not available in many parts of the world. Also, many people identified as having diabetes based on HbA1c will not have diabetes by direct glucose measurement.

“An HbA1c of 6.5% is recommended as the cut point for diagnosing diabetes. A value of less than 6.5% does not exclude diabetes diagnosed using glucose tests. and vice versa.

“The use of HbA1c can avoid the problem of day-to-day variability of glucose values, and importantly it avoids the need for the person to fast and to have preceding dietary preparations. These advantages have implications for early identification and treatment which have been strongly advocated in recent years.

“The utility and convenience of HbA1c compared with measures of plasma glucose for the diagnosis of diabetes needs to be balanced against the fact that it is unavailable in many countries despite being a recognized valuable tool in diabetes management.”

As stated above, despite the advantages in using HbA1c, testing for HbA1c is unavailable in many parts of the world because it is unaffordable in most low and middle-income countries. The presently available quantitative HbA1c tests require obtaining a blood sample, lysing red blood cells in the sample with a lysis buffer to release the haemoglobin in the red blood cells, placing the lysed sample in a test cartridge and inserting the test cartridge into an correctly calibrated machine or analyser that determines the percentage of HbA1c in the total haemoglobin (Hb). Appreciably, this requires the test to be done in a laboratory or clinic with a stable power supply, even if the blood sample may be obtained elsewhere. Unfortunately, in many parts of the world, it is prohibitively costly to set up such laboratories or clinics, resulting in HbA1c not being available as a means of diagnosing and managing diabetes in the local population.

Although there has been an attempt to simplify the HbA1c test by providing a HbA1c test kit that contains a test strip with two lines that become coloured to indicate the test result, in this test, HbA1c value is determined by the user visually comparing the coloration of the lines. If the HbA1c line is almost the same colour as the Hb line, the results are normal. If the HbA1c line is darker than the Hb line, diabetes is suspected. Unfortunately, this does not provide any actual quantitative value of HbA1c and is subject to the user's personal interpretation of how much the HbA1c line is perceived to be darker than the Hb line.

From the above, it can be seen that there is a need for an affordable and feasible way to test for HbA1c that gives a reliable quantitative result, in order to make available the use of HbA1c for patients all over the world.

SUMMARY OF INVENTION

According to a first aspect, there is provided a haemoglobin test kit comprising: a lateral flow test strip having a sample collection portion, a conjugate portion and a plurality of test lines downstream of the conjugate portion, the conjugate portion comprising haemoglobin antibody conjugated with coloured particles to bind with haemoglobin in a sample fluid; wherein each test line comprises a different concentration of haemoglobin antibody, and wherein each test line comprises a particular concentration of haemoglobin antibody tuned to bind with haemoglobin in the sample fluid.

Concentration of haemoglobin antibody in the plurality of test lines may increase for successive test lines in a downstream direction.

A most downstream visible test line may indicate percentage of haemoglobin contained in the sample fluid.

The haemoglobin test kit may further comprise visible markings that correspond with locations of the test lines in the test strip, the visible markings each indicating a particular percentage of haemoglobin that may be contained in the sample fluid.

The haemoglobin test kit may further comprise a further set of markings indicating blood glucose levels that correspond to specific percentages of haemoglobin in the visible markings.

The haemoglobin may be glycated haemoglobin.

DETAILED DESCRIPTION

Exemplary embodiments of the haemoglobin test kit10will be described below with reference toFIGS. 1 and 2.

As shown inFIGS. 1 and 2, the haemoglobin test kit10is a lateral flow test kit comprising a lateral flow test strip40. The test strip40has a sample collection portion41, a conjugate portion42and a plurality of test lines43downstream of the conjugate portion42. The test strip40preferably also has at least one control line47downstream of the plurality of test lines43, and an absorbent pad49at the downstream end of the test strip40. The downstream direction is indicated by arrow99inFIGS. 1 and 2. It should be noted that inFIG. 2where the lateral flow test strip40can be seen, the test lines43and control lines47are rendered visible only for illustration purposes. In reality, the test lines43and control lines47are invisible before use of the haemoglobin test kit10.

As shown inFIG. 1, the haemoglobin test kit10is provided with visible markings36that correspond with locations of the test lines43in the test strip40. The markings36each indicate a particular percentage of haemoglobin that may be in the sample fluid. Preferably, the haemoglobin test kit10also comprises a further set of markings38to indicate blood glucose levels (in mmol/l) that correspond with specific percentages of haemoglobin.

In the test strip40, each test line43comprises a different concentration of haemoglobin antibody. The haemoglobin antibody may be an antibody for haemoglobin (Hb) or glycated haemoglobin (HbA1c), according to which type of haemoglobin the test kit is intended to be used for. Each test line comprises a particular concentration of haemoglobin antibody that is tuned to bind with haemoglobin in a sample fluid that flows through the test strip40. Before binding with the haemoglobin antibody in a test line, haemoglobin in the sample fluid is bound to a conjugate that becomes visible at a test line when a sufficient quantity of haemoglobin in the sample fluid has been immobilized at that test line.

The conjugate is provided on the test strip40in a conjugate portion42adjacent the sample collection portion41. The conjugate may comprise any known coloured particles such as colloidal gold nanoparticles or latex microspheres conjugated with haemoglobin antibody. haemoglobin in the sample fluid thus binds with the haemoglobin antibody in the conjugate to pick up the coloured particles, forming a complex comprising haemoglobin conjugated with coloured particles. As the complex flows across the test lines43, haemoglobin in the complex also binds with the haemoglobin antibody at the test lines to immobilize the coloured particles at the test lines. In this way, a particular test line becomes visible only when a sample fluid that flows across that particular test line43contains at least a same percentage of haemoglobin as the particular percentage of haemoglobin for which the particular test line43is tuned to bind with and indicate, as a result of a sufficient concentration of coloured particles being immobilized at the particular test line together with the haemoglobin in the complex.

The concentration of haemoglobin antibody comprised in each test line43increases for successive test lines43in the downstream direction99. Thus, referring toFIG. 1, the test line at the 6.0% marking comprises a higher concentration of haemoglobin antibody than the test line at the 5.5% marking. In this way, when a sample fluid is placed on the sample collection portion41and flows across the test lines43, if the sample fluid contains haemoglobin, the percentage of haemoglobin in the sample fluid may be quantitatively known by observing which of the test lines43become visible in a reaction window33of the haemoglobin test kit10. Among the test lines that become visible, the most downstream visible test line indicates the actual percentage of haemoglobin in the sample fluid.

For example, referring toFIG. 1, when a sample fluid containing 7.0% haemoglobin is tested using the haemoglobin test kit10, test lines43at the 5.5%, 6.0%, 6.5%, and 7.0% markings will become visible. This is because the 7.0% haemoglobin present in the sample fluid is sufficient to bind with the concentration of haemoglobin antibody comprised by the test lines at the 5.5%, 6.0%, 6.5%, and 7.0% markings to cause these test lines to become visible. The remaining test lines that indicate a haemoglobin percentage greater than 7.0% stay invisible because the 7.0% haemoglobin present in the sample fluid is insufficient to bind with the remaining test lines to cause the remaining test lines to become visible. This is because the remaining test lines comprise higher concentrations of haemoglobin antibody that are tuned to bind with and indicate higher percentages of haemoglobin than 7.0%. In this example, the 7.0% line being the most downstream of the visible test lines thus indicates that the sample fluid has 7.0% haemoglobin.

Similarly, if another sample fluid is tested with the haemoglobin test kit10and the test lines at the 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, and 8.5% markings become visible while the remaining test lines43stay invisible, it can be concluded that the sample fluid contains 8.5% haemoglobin.

The control line47comprises antibody for binding with the haemoglobin antibody in the conjugate to indicate that the test is valid when the control line47becomes visible.

The sample fluid typically comprises a mixture of a patient's blood sample and a commercially available lysis buffer. In use, the sample fluid may be prepared by lancing a patient's fingertip to obtain a drop of blood, placing the drop of blood in about 0.5 ml of the lysis buffer, and agitating the mixture of the drop of blood and the lysis buffer for about 5 seconds to obtain the sample fluid.

In the exemplary embodiment shown inFIGS. 1 and 2, the haemoglobin test kit10comprises a base sheet20, a sealing sheet30having a sealed sample collection31opening before use of the haemoglobin test kit10, the lateral flow test strip40sealed between the base sheet20and the sealing sheet30before use of the haemoglobin test kit10, and a top sheet50. The sealing sheet30is provided with a transparent portion configured as a reaction window33aligned over the test lines43and the control line47so that they43,47, can be seen through the reaction window33. The top sheet50is configured to be attached to the sealing sheet30before use of the haemoglobin test kit10to keep the sample collection opening31sealed. As the top sheet50is layered over all of the sealing sheet30, the top sheet50also comprises a transparent portion53aligned with the reaction window33of the sealing sheet30to allow the test lines43and the control line47to be seen through both the sealing sheet30and the top sheet50layers.

In an alternative embodiment, the top sheet50may be layered only partially over the sealing sheet30without being layered over the reaction window33, in which case no transparent portion needs to be provided in the top sheet50.

The base sheet20, sealing sheet30and top sheet50are preferably rectilinear in shape and of the same size so that the haemoglobin test kit10is a simple, almost flat rectangular package.

As shown inFIG. 2, the top sheet50is further configured to be at least partially detached from the sealing sheet30to open the sample collection opening31during use of the haemoglobin test kit10. When the sample collection opening31has been opened, the sample collection portion41of the test strip40is exposed through the sample collection opening31and can then receive a fluid analyte thereon. This may be achieved by layering the top sheet50over the sealing sheet30and providing the top sheet50with appropriately located die cut lines57(e.g. on at least one side of the sample collection opening31) to allow the top sheet50to be at least partially peeled away from the sealing sheet30.

The sample collection opening31is preferably sealed by a cover38before use of the haemoglobin test kit10. The cover38is attached to the top sheet50such that at least partially detaching the top sheet50from the sealing sheet30detaches the cover38from the sealing sheet30to open the sample collection opening31. The cover38is preferably integral with or part of the sealing sheet30before use of the haemoglobin test kit10.

The top sheet50is preferably also configured to be re-attachable to the sealing sheet30to cover the sample collection opening31after use of the haemoglobin test kit10, in order to prevent the sample fluid on the sample collection portion41from coming into contact with another object. This is a safety or hygiene feature to minimize or prevent human handlers of the used haemoglobin test kit10from being contaminated by contaminants in the sample fluid, and to minimize or prevent cross contamination with other used haemoglobin test kits10.

The base sheet20, sealing sheet30and at least one top sheet50each preferably comprise a moisture barrier polymeric film so that the at least one test strip40is kept well sealed between the base sheet20and sealing sheet30before use of the haemoglobin test kit10.

In this way, the haemoglobin test kit10requires no additional moisture barrier packaging to keep the at least one test strip40stable during storage and transportation of the haemoglobin test kit10before use. This also greatly reduces the size of the haemoglobin test kit10and the space it takes up, which would have a significant impact particularly when haemoglobin test kits need to be moved in areas with poor transportation networks or accessibility. For example, a single healthcare worker going on foot to a remote location will be able to take with him or her a great many more of the haemoglobin test kits10of the present invention in a single hand-carry bag or case or even clothing pocket as compared to existing haemoglobin test kits with plastic cassettes in foil bags that would be significantly more bulky to carry. Doing away with the need for an additional moisture barrier foil bag and plastic cassette also significantly reduces the cost of the haemoglobin test kit10of the present invention, since each foil bag and each plastic cassette contributes to the total cost of each traditionally available haemoglobin test kit.

In addition, the haemoglobin test kit10is preferably provided with at least one quick response (QR) code80on the haemoglobin test kit10, more preferably located on the top sheet50for easy access. The at least one QR code80allows information such as manufacturing date, expiry date and source information of the at least one test strip40and the haemoglobin test kit10itself to be stored and retrieved, as well as allowing the haemoglobin test kit10to be associated or tagged with a single specific source of the fluid analyte. The specific source may be a patient or any other sample fluid, depending on the usage application of the haemoglobin test kit10. The QR code is preferably located on a part58of the top sheet50where the part58of the top sheet50is never detached from the sealing sheet30, or on a part of the sealing sheet30that is not overlayed by a top sheet50(depending on the configuration of the haemoglobin test kit10). In this way, the quick response code80is never separated from the test strip40in the haemoglobin test kit10after use, and each test strip40can be correctly traced to its specific sample fluid source. Having the quick response code80on each haemoglobin test kit10allows each haemoglobin test kit10to be indelibly and indubitably associated with only one specific sample fluid source, thereby minimizing or preventing mix-ups in test results from occurring.

The haemoglobin test kit10is preferably provided or sold together with the lysis buffer to allow diabetes patients to prepare the sample fluid and test for haemoglobin using the haemoglobin test kit10at home. In this way, the present invention provides a low cost, low bulk haemoglobin test kit10that can be used at the point of care and associated with a specific sample fluid source (e.g. a specific patient) without requiring a costly laboratory or clinic set-up to run the tests for haemoglobin.

Whilst there has been described in the foregoing description exemplary embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations in details of design, construction and/or operation may be made without departing from the present invention. For example, while it has been described that the base sheet, sealing sheet and top sheet are preferably made of a moisture barrier polymeric film, they may alternatively be made of appropriately laminated paper with sufficient moisture barrier properties required for stable storage of the test strips therein. It is further envisaged that in various embodiments of the haemoglobin test kit, the top sheet may or may not be layered over all of the sealing sheet so long as it is layered over the sample collection opening to keep the sample collection opening sealed before use of the haemoglobin test kit. In addition to the above described examples and alternative configurations, any other possible configurations of lateral flow test kits may be used to house the test strip40so long as the test strip comprises the sample collection portion and the plurality of test lines as described above.