Haemoglobin A1c: difference between revisions
Diff·revision 3 → 4·08:18, 30 Aug 2024
Difference between revision 3 and revision 4 of Haemoglobin A1c. 5 lines changed; the page grew by 721 bytes.
| Revision 3 — 06:51, 19 Aug 2024 SerialCommaSeb (talk) add the interference the assay is known to be subject to 1,822 bytes ±0 | Revision 4 — 08:18, 30 Aug 2024 MelanocortinMil (talk) rm the extrapolation from a research assay to a clinical one 2,543 bytes +721 | ||
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| 11 | It is reported in two unit systems: mmol/mol under the IFCC reference method, and percentage under the older DCCT-aligned convention. Both appear in the literature and conversion between them is defined.{{r|nathan2008}} | 11 | It is reported in two unit systems: mmol/mol under the IFCC reference method, and percentage under the older DCCT-aligned convention. Both appear in the literature and conversion between them is defined.{{r|nathan2008}} |
| 12 | 12 | ||
| + | 13 | Its principal limitation follows from its mechanism: anything that alters red-cell lifespan alters the result independently of glucose. Haemolysis and blood loss lower it; iron deficiency and reduced turnover raise it.{{r|ada2024}} | |
| + | 14 | ||
| 13 | == What it measures == | 15 | == What it measures == |
| 14 | Glycation is a slow non-enzymatic reaction between glucose and the N-terminal valine of the haemoglobin β-chain. Its extent depends on both glucose concentration and exposure time, and because red cells are replaced continuously the population of cells sampled at any moment carries a weighted history.{{r|nathan2008}} | 16 | Glycation is a slow non-enzymatic reaction between glucose and the N-terminal valine of the haemoglobin β-chain. Its extent depends on both glucose concentration and exposure time, and because red cells are replaced continuously the population of cells sampled at any moment carries a weighted history.{{r|nathan2008}} |
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| 16 | The weighting is not uniform: roughly half the value reflects the preceding month, and the remainder the two months before. A change made three weeks ago is therefore only partly expressed.{{r|ada2024}} | 18 | The weighting is not uniform: roughly half the value reflects the preceding month, and the remainder the two months before. A change made three weeks ago is therefore only partly expressed.{{r|ada2024}} |
| 17 | 19 | ||
| + | 20 | Estimated average glucose can be derived from HbA1c by a published regression, and the derivation carries substantial individual variation — two people with identical HbA1c can have appreciably different mean glucose.{{r|nathan2008}} The measure is a laboratory determination with its own method dependence, as any determination is.{{r|usp1503}} | |
| + | 21 | ||
| 18 | == References == | 22 | == References == |
| 19 | {{reflist}} | 23 | {{reflist}} |
| 20 | <ref name="ada2024">American Diabetes Association. "Standards of Care in Diabetes." ''Diabetes Care'' 47(Suppl 1) (2024).</ref> | 24 | <ref name="ada2024">American Diabetes Association. "Standards of Care in Diabetes." ''Diabetes Care'' 47(Suppl 1) (2024).</ref> |
| 21 | <ref name="nathan2008">Nathan DM, Kuenen J, Borg R, et al. "Translating the A1C assay into estimated average glucose values." ''Diabetes Care'' 31(8):1473–1478 (2008). PMID 18540046.</ref> | 25 | <ref name="nathan2008">Nathan DM, Kuenen J, Borg R, et al. "Translating the A1C assay into estimated average glucose values." ''Diabetes Care'' 31(8):1473–1478 (2008). PMID 18540046.</ref> |
| + | 26 | <ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, ''Quality Attributes of Synthetic Peptide Drug Substances''.</ref> | |
| 22 | 27 | ||
| 23 | {{DEFAULTSORT:Haemoglobin A1c}} | 28 | {{DEFAULTSORT:Haemoglobin A1c}} |