High-density lipoprotein assay device and method
An assay device and method for measuring the concentration of HDL-associated cholesterol in a blood-fluid sample are described. The assay design is such that removal of non-HDL lipoproteins from a sample and assay of HDL cholesterol in the sample occur without interruption of the assay. The device also prevents interference by reagents used for the HDL assay with other assays carried out on the same sample.
1. An assay device for measuring serum cholesterol associated with high-density lipoproteins (HDL) in a blood fluid sample also containing low density lipoproteins (LDL) or very low density lipoproteins (VLDL), the device comprising:
a sample distribution matrix effective to distribute a blood fluid sample from a sample application region within the matrix to one or more sample collection regions within the matrix;
an HDL assay element, in which HDL concentration can be assayed, spaced apart from said sample distribution matrix,
a reagent pad, disposed between said HDL assay element and said sample distribution matrix, and spaced apart from said matrix, said reagent pad containing a reagent effective to selectively remove non-HDL lipoproteins from the fluid sample, and
mounting means effective (a) to maintain said device in a sample-distribution position, wherein said HDL assay element and reagent pad are spaced apart from said matrix, and (b) to transfer said device to a test position, whereby the HDL assay element is placed or maintained in contact with the reagent pad, and the reagent pad is, concurrent with or subsequent to said contact, brought into contact with said matrix.
2. The device of claim 1 , wherein a lower surface of the HDL assay element is attached to an upper surface of the reagent pad.
3. The device of claim 1 , further comprising a cassette body to which said sample distribution matrix is attached.
4. The device of claim 3 , further comprising a reaction bar to which said HDL assay element is attached.
5. The device of claim 4 , wherein said mounting means is effective to attach said reaction bar to said cassette body and to adjust the relative positions of the reaction bar and cassette body between said sample-distribution position and said test position.
6. The device of claim 3 , wherein said cassette body further comprises a well for containing said blood fluid sample and a sieving pad for removing cellular blood components from said blood fluid sample, in fluid communication with said sample application region.
7. The device of claim 4 , further comprising additional assay elements attached to said reaction bar, such that said pads are brought into contact with said sample collection regions when the device is transferred to the testing position.
8. The device of claim 1 , wherein said mounting means is further effective to (c) transfer the device from said test position to a position in which said HDL assay element and reagent pad are spaced apart from said matrix.
9. The device of claim 1 , wherein said reaction bar is optically transparent or includes windows through which said assay elements are visible.
10. The device of claim 1 , wherein said reagent includes a sulfonated polysaccharide.
11. The device of claim 1 , wherein said reagent pad is impregnated with said reagent in a form which is soluble in said fluid sample, and is of a material effective to entrap precipitated non-HDL lipoproteins within the reagent pad.
12. The device of claim 1 , wherein said reagent is immobilized to said reagent pad.
13. The device of claim 1 , wherein said HDL assay element contains reagents which, in the presence of HDL-associated cholesterol, produce a change in the assay element which can be detected optically.
14. The device of claim 1 , wherein said HDL assay element comprises a biosensor.
15. The device of claim 14 , wherein said biosensor is effective to measure production of oxygen or hydrogen peroxide which is dependent on HDL-associated cholesterol concentration within said element.
16. The device of claim 1 , wherein said reagent pad comprises a porous polymeric membrane.
17. The device of claim 15 , wherein said reagent pad is an asymmetric polymeric membrane, having a smaller pored surface and an opposite, larger pored surface.
18. The device of claim 17 , wherein said membrane is oriented such that its smaller pored surface faces the HDL assay element.
19. The device of claim 1 , wherein each of said HDL assay element and said reagent pad is an asymmetric polymeric membrane, and said membranes are laminated such that the smaller pored surface of the reagent pad contacts a larger pored surface of the HDL assay element.
20. A method of measuring serum cholesterol associated with high-density lipoproteins (HDL) in a blood fluid sample also containing low density lipoproteins (LDL) or very low density lipoproteins (VLDL), comprising
(a) contacting the sample with an absorptive sample distribution matrix through which said sample is distributed to one or more sample collection sites;
(b) bringing into contact with such a sample collection site, a first surface of a reagent pad, to which said sample is transferred, containing a reagent effective to selectively remove non-HDL lipoproteins from the fluid sample,
wherein an opposite surface of said reagent pad is in simultaneous contact with an HDL assay element, containing assay reagents effective to produce an indication of HDL cholesterol concentration, such that successive sample volumes proceed from said reagent pad to said HDL assay element, and
(c) determining the level of HDL cholesterol in said sample by detection at said HDL assay element.
21. The method of claim 20 , further comprising the step of breaking said contact between the sample collection site and the first surface of the reagent pad, when a desired amount of sample has been transferred.
22. The method of claim 20 , wherein said reagent pad is impregnated with said reagent in a form which is soluble in said fluid sample, and is of a material effective to entrap precipitated non-HDL lipoproteins within the reagent pad.
23. The method of claim 20 , wherein said reagent effective to selectively remove non-HDL lipoproteins is immobilized to said reagent pad.
24. The method of claim 22 , wherein said reagent pad comprises an asymmetric polymeric membrane, having a smaller pored surface and an opposite, larger pored surface.
25. The method of claim 24 , wherein said membrane is oriented such that its smaller pored surface faces said HDL assay element.
26. The method of claim 20 , wherein said HDL assay element comprises a biosensor.
27. The method of claim 26 , wherein said biosensor is effective to measure production of oxygen or hydrogen peroxide which is dependent on HDL-associated cholesterol concentration within said element.
28. The method of claim 24 , wherein each of said HDL assay element and said reagent pad is an asymmetric polymeric membrane, and said membranes are laminated such that the smaller pored surface of the reagent pad contacts a larger pored surface of the HDL assay element.