The relative merits of haemoglobin A1c and fasting plasma glucose as first-line diagnostic tests for diabetes mellitus in non-pregnant subjects
✍ Scribed by Wiener, K.; Roberts, N.B.
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 119 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0742-3071
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✦ Synopsis
HbA 1c was measured by high-performance ion-exchange chromatography in 401 nonpregnant patients undergoing oral glucose tolerance tests (OGTT). All those with HbA 1c Ͼ6.2 % (reference range 3.8-5.5 %) had diabetic OGTT (sensitivity 41 %, specificity 100 %). Although a fasting plasma glucose (FPG) cut-off Ն7.0 mmol l -1 , as recommended by the American Diabetes Association (ADA), had greater sensitivity (78 %), false positives (12 %) limited its usefulness, so more diagnostic confidence could be placed in a positive HbA 1c . In agreement with the ADA, we found FPG gave only slightly lower diabetes prevalence than the OGTT, but this masked a significant number of individual discrepancies (false positives and negatives) cancelling out each other. The new ADA category of impaired fasting glucose did not correlate well with impaired glucose tolerance. HbA 1c is insufficiently sensitive as a direct substitute for the OGTT. A third of subjects diabetic on OGTT had normal HbA 1c values, so it cannot exclude diabetes as currently defined, but HbA 1c screening could make sufficient positive diagnoses to reduce our non-pregnant OGTTs by one-fifth. If a 'risk threshold' for diabetic complications could be applied to HbA 1c , it could replace the OGTT as a more pragmatic diagnostic/prognostic test.