Challenges in HbA1c Analysis and Reporting in Patients with Variant Hemoglobins.
Hemoglobin A1c (HbA(1)c) is a well-established indicator of mean glycemia. The presence of genetic variants of hemoglobin can profoundly affect the accuracy of HbA(1)c measurements. Variants of hemoglobin especially Hemoglobin E (HbE) is prevalent in South East Asia including Bangladesh. The objective of our study is to compare the HbA(1)c values measured on high performance liquid chromatography (HPLC) and Turbidimetric Inhibition Immunoassay (TINIA) in diabetic patients with variant hemoglobins including HbE. A total of 7595 diabetic patients receiving treatment at BIRDEM General Hospital were analyzed for HbA(1)c results within a period of two months from December 2013 to January 2014. Seventy two cases out of 7595 (0.95%) had either undetectable or below normal HbA(1)c levels (males-33 and females-39; ratio = 0.82:1) by HPLC method. In 34(0.45%) cases, HbA(1)c value was undetectable by HPLC method but was in the reportable range by TINIA method. In the other 38 (0.55%) cases, HbA(1)c levels were below the reportable range (<4%) by HPLC method but were in the normal or higher range by TINIA method. TINIA method did not agree with HPLC method on Bland Altman plot in the 38 cases with below normal HbA(1)c levels, [Mean bias -5.2(-9.3 to 1.0), 95% CI] but agreed very well [mean bias -0.21 (-0.84 to 0.42), y=1.1037+0.776X; r(2)=0.30, p<0.01] in controls. In control group mean MCV was 83.80±7.48 and in study group was 73.65±10.44. Alkaline electrophoresis confirmed the variant hemoglobin to be HbE. The fasting blood sugar levels of all the 72 cases correlated strongly with TINIA method (r(2) =0.75, p<0.0001) but not with HPLC (r = 0.24, p=0.13). In our regions where populations have a high prevalence of Hb variant, proper knowledge of hemoglobin variants which affect the measurements HbA(1)c level is essential. MCV of 80fl or below may serve as a rough guide to select samples that require analysis by TINIA method. Moreover, HPLC may be a convenient and inexpensive tool for screening of hemoglobinopathies especially among diabetic population in Bangladesh. It may therefore be helpful in improving management of complications related to both anaemia and iron overload.