Influence of hemoglobin variants and derivatives on glycohemoglobin determinations, as investigated by 102 laboratories using 16 methods

Abstract

Influences of hemoglobin (Hb) variants (HbSS, HbCC, beta-thalassemia, HbAE, HbAS, HbAC, hereditary persistent HbF) and Hb derivatives (carbamylated- and acetylated-Hbs, Schiff base, and those formed in stored blood) on results of glyco-Hb assays by 102 laboratories using 16 different methods were investigated. Affinity chromatography shows deviating results only with homozygous Hb S and C. Correct interpretation of results from patients with decreased erythrocyte half-lives requires previous knowledge on this condition. Measurements of HbA1c by HPLC and electrophoresis are obviously unsuitable for homozygous hemoglobinopathies; for heterozygous hemoglobinopathies and Hb synthesis variants, HbA1c should be expressed as percentage of HbA0 + HbA1c; abnormal Hbs are usually recognized; both carbamylated- and acetylated-Hbs interfere and Schiff base must be eliminated. Except for stored blood, all Hb variants and derivatives gave erroneous results with disposable ion-exchange columns. Dako's immunoassay is not affected by Hb derivatives; glycated Hb variants are not recognized as glyco-Hb and percentages are consequently too low. Glyco-Hb by the immunoassay of Bayer (performed by one laboratory) is not affected by Hb variants and derivatives.

The effect of iron deficiency anaemia on the levels of haemoglobin subtypes: possible consequences for clinical diagnosis

“…Clinical laboratory diagnosis is an essential precursor to therapeutic intervention in most diseases. In this context, it is important to exclude interference by other conditions that may give false‐positive or negative results, leading to inappropriate management (Weykamp et al, 1993; The Thalassemia Working Party of the BCSH General Haematology Task Force., 1994). Estimation of haemoglobin subtypes is important for the diagnosis of certain clinical conditions.…”

“…In clinical laboratories, haemoglobin subtypes are reported as percentages of total haemoglobin. In iron deficiency, the decreased concentration of total haemoglobin may influence the percentages of different haemoglobin subtypes (Weatherall, 1983; Nathan & Oski, 1993; Weykamp et al ., 1993; The Thalassemia Working Party of the BCSH General Haematology Task Force., 1994). Iron deficiency is thus a potential source of diagnostic interference in these tests.…”

Haemoglobin A1c in donor erythrocytes

“…Surprisingly, a recent study found neither a significant increase in donor erythrocyte (RBC) glycated haemoglobin (HbA1c) nor an effect on transfusion recipients (Spencer et al , 2011). We hypothesized that the discrepancy is related to the pre‐analytical physical and chemical conditions under which glycation occurs rather than to differences in specificity of the analytical methods for HbA1c (Weykamp et al , 1993). Therefore, we studied HbA1c in donor RBC in preservative solutions containing different glucose concentrations, after various 4 °C storage intervals and after RBC incubation at 20 and 37 °C.…”

Considerations on blood glucose management in Type 2 diabetes mellitus

“…Physicians need to be aware that some medical conditions, such as disorders of haemoglobin metabolism, need to be taken into account when assessing HbA 1c levels 30, 31. For example, haemoglobin variants such as high levels of fetal haemoglobin (HbF) may interfere with standard assays for HbA 1c , leading to false estimates of HbA 1c concentrations 32.…”