INFLUENCE OF HEMOGLOBIN-VARIANTS AND DERIVATIVES ON GLYCOHEMOGLOBIN DETERMINATIONS, AS INVESTIGATED BY 102 LABORATORIES USING 16 METHODS

Influences of hemoglobin (Hb) variants (HbSS, HbCC, beta-thalassemia, HbAE, HbAS, HbAC, hereditary persistent HbF) and Hb derivatives (carba mylated- and acetylated-Hbs, Schiff base, and those formed in stored b lood) on results of glyco-Hb assays by 102 laboratories using 16 diffe rent methods were investigated. Affinity chromatography shows deviatin g results only with homozygous Hb S and C. Correct interpretation of r esults from patients with decreased erythrocyte half-lives requires pr evious knowledge on this condition. Measurements of HbA1c by HPLC and electrophoresis are obviously unsuitable for homozygous hemoglobinopat hies; for heterozygous hemoglobinopathies and Hb synthesis variants, H bA1c should be expressed as percentage of HbA0 + HbA1c; abnormal Hbs a re usually recognized; both carbamylated- and acetylated-Hbs interfere and Schiff base must be eliminated. Except for stored blood, all Hb v ariants and derivatives gave erroneous results with disposable ion-exc hange columns. Dako's immunoassay is not affected by Hb derivatives; g lycated 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.