Glycated protein assay
Methods, devices, and reagents are described for performing assays for hemoglobin Ale, glycated albumin, and other glycated proteins. The methods involve a ratio determination between glycated protein and non-glycated protein. In some applications, the assay utilizes LOCI for signal generation. This invention is directed to assays and corresponding devices and reagents for detection of glycated protein, particularly including glycated hemoglobin. As is generally understood, such detection is useful in the management of blood glucose levels in diabetic patients and for monitoring the status of pre-diabetic individuals.
1. A method for determining the fraction of a glycated protein in a sample, comprising
contacting (i) a labeled, specific binding member specific for total protein or a peptide corresponding to total protein or un-glycated protein or peptide, and (ii) a labeled, specific binding member specific for glycated protein or peptide with
a) a sample containing said protein or a peptide of said protein susceptible to glycation; and
b) a non-sample-derived glycated version of said protein or peptide; or
c) a non-sample-derived unglycated version of said protein or peptide;
detecting a plurality of signals, with at least a first signal indicative of the level of glycated protein, and at least a second signal indicative of the level of total protein or unglycated protein; and
determining a ratio between glycated protein and un-glycated protein, or between glycated protein and total protein, as an indication of the fraction of said protein which is glycated in said sample,
wherein said contacting is performed under competitive binding conditions, and wherein said first signal and said second signal are distinguishable; and
wherein the sample is contacted with a control labeled binding member that specifically binds a target not in the sample and said control labeled binding member is later detected, wherein the detected amount of control labeled binding member is used to normalize signals for the level of glycated protein or total protein or both.
2. The method of claim 1 , wherein said peptide is cleaved by trypsin, endopeptidase GluC, pepsin, or a prolyl endopeptidase.
3. The method of claim 1 , wherein said first and second signals are fluorescent signals or TRF signals.
4. The method of claim 1 , wherein said detecting is performed on a lateral flow assay device, wherein said device comprises a detection zone comprising an immobilization site for glycated protein or peptide and an immobilization site for said total protein or peptide corresponding to total protein, wherein signal corresponding to glycated protein or peptide and signal corresponding to the total protein or the peptide corresponding to total protein, are detected separately.
5. The method of claim 4 , wherein said control labeled binding member is immobilized in an immobilization site comprising immobilized versions of the target not in the sample.
6. The method of claim 5 , wherein said target not in the sample is a protein from a non-human species.
7. The method of claim 1 , wherein said detecting is performed on a lateral flow assay device, wherein said device comprises a detection zone comprising an immobilization site for glycated protein or peptide and an immobilization site for un-glycated protein or peptide, wherein signal corresponding to glycated protein or peptide and signal corresponding to un-glycated protein or peptide are detected separately.
8. The method of claim 1 , wherein a plurality of isoforms of said protein or a peptide thereof are distinguishably detected.
9. The method of claim 8 , wherein said plurality of isoforms are detected in a single zone.
10. The method of claim 8 , wherein said isoforms are detected in separate zones.
11. The method of claim 8 , wherein said protein is hemoglobin beta-chain and said isoforms include at least two of HbA, HbC, HbD Punjab, HbE, and HbS.
12. The method of claim 1 , wherein said protein is human hemoglobin.
13. The method of claim 12 , wherein said glycated peptide is HbA1C N-terminal peptide.
14. The method of claim 1 , wherein a plurality of isoforms of said protein or a peptide thereof are distinguishably detected.
15. The method of claim 14 , wherein said protein is hemoglobin beta-chain and said isoforms include at least two of HbA, HbC, HbD Punjab, HbE, and HbS.
16. The method of claim 14 , wherein said protein is hemoglobin beta-chain and said isoforms include HbC, HbD Punjab, HbE, and HbS.
17. The method of claim 8 , wherein said protein is hemoglobin beta-chain and said isoforms include HbE and HbS.
18. The method of claim 1 , wherein the sample is from a human and the target not in the sample is a protein from a non-human species.