Interference with glycated hemoglobin by hemoglobin F may be greater than is generally assumed

An automated electrophoretic method to measure glycated hemoglobin (Hb A1) was compared with manual affinity methods. Good correlation between methods was found. The electrophoretic method showed good run-to-run precision, good linearity, was free from interference by the labile aldimine fraction, and required less time and considerably less consumable expense than the affinity methods. However, as previously reported, Hb F comigrating with Hb A1 caused spurious increases in glycated Hb levels as compared with the affinity methods. This effect was linearly dependent on the Hb F concentration. Using the discrepancy between concentrations of Hb A1 by electrophoresis and glycated hemoglobin by affinity methods, 330 patients were screened in two hospitals for Hb F. A 12% frequency of elevated Hb F (defined as a level that is more than 2%) was found in patients from a community-tertiary care hospital, which is significantly greater than the 1.5% frequency commonly thought to occur in the adult population at large, whereas patients from a Veterans Administration Hospital showed an elevated frequency of 2.2%. Based on this and other studies, it is concluded that the frequency of elevated Hb F in adults may very substantially among different medical centers. The authors recommend against using this method and suggest that laboratories that persist in using it should periodically assess the frequency in patients with Hb F levels greater than 2% of total hemoglobin, replacing the method if an unacceptably high frequency is found.