Influence of in vivo hemoglobin carbamylation on HbA1c measurements by various methods.

Increased carbamylated hemoglobin formed in erythrocytes during uremia may interfere with HbA 1c assays, but few studies compared directly both parameters. We measured carbamylated hemoglobin by HPLC in 45 non-diabetic uremic patients (16 with acute and two with chronic renal failure, 27 with transplant recipients) as 57.8 ± 22.3 μg carbamylvaline /g Hb (mean ± standard deviation) vs. 31.6 ± 5.1 in 15 controls (+83%, p 60 μg carbamylvaline/g Hb) vs. low (< 45) carbamylated hemoglobin values (+0.08 to 0.25% of total Hb), but differences were not significant. Minor peaks on the chromatograms were however increased in parallel to carbamylated hemoglobin. HbA 1c values over 6% were found in 4, 1, 2 and 0 samples, with HPLC 1, 2, 3 and immunoassay, respectively. Fructosamine values were not significantly altered. Our results show that Hb adducts, whether due to carbamylation or to other chemical reactions, interfere to a variable extent with different HbA 1c assay methods, and confirm that HbA 1c values should be interpreted with caution in uremic patients.