Difference in hemoglobin %A2 between homozygous hemoglobin A and hemoglobin S-trait patients as measured by capillary electrophoresis

Abstract Introduction/Objective Quantitation by high-performance liquid chromatography (HPLC) of hemoglobin %A2 is often not used in evaluation for thalassemia of hemoglobin S-trait patients, due to analytical interference from glycated hemoglobin S1d to increase %A2. In contrast, an increase in %A2 for S-trait when measured by capillary electrophoresis (CE) has been reported, without known analytical interference. This observation has not been re- evaluated in modern versions of CE, however. For validation exercises associated with startup of CE at our institution, we compared distributions of %A2 among A patients and S-trait patients using Sebia “Capillarys® 2” CE. Methods/Case Report %A2 is provided in two Sebia “Capillarys® 2” methods: analysis of A1c (method 1, M1) and analysis of hemoglobin variants (method 2, M2). To minimize effect of potential preselection for thalassemia among M2 samples, we first evaluated distributions of %A2 for A and S-trait among M1 samples. We then evaluated correlation of A2 measurements between M1 and M2. Statistical analyses were conducted using R programming. Results (if a Case Study enter NA) Using M1, %A2 for S-trait patients (2.61±0.31%, n=116) was higher than for A patients (2.11±0.27%, n=108) (p0.25): for A, M1/M2=0.89±0.05 (n=35); for S-trait, M1/M2=0.88±0.05 (n=32). Decreased %A2 by M1 compared to M2 may in part be due to separation in M1 of a glycated form of A2. Using M2, %A2 for S-trait patients (3.05±0.29%, n=32) was higher than for A patients (2.41±0.29%, n=35) (p