Agreement between HbA1c measured by DCA 2000 and by HPLC: Effects of fetal hemoglobin concentrations

Abstract Background In subjects with type 1 diabetes, persisting elevations of fetal hemoglobin (HbF) have been demonstrated. This study evaluated whether HbF levels typically seen in type 1 diabetes (up to 3%) interfere with glycohemoglobin determinations using a common immunologic method (DCA 2000 ™ ). Methods HbA 1c was measured by high-performance liquid chromatography (HPLC) using a Diamat ™ analyzer in 90 type 1 diabetics with parallel determinations of HbF. Results were compared with HbA 1c concentrations obtained using DCA 2000 ™ . Results Reproducibility was good for both methods with coefficients of variation r 2  = 0.939, p ™ immunologic method tended to underestimate and at higher concentrations tended to overestimate HbA 1c when compared with Diamat ™ . Stepwise linear regression with HbA 1c (DCA 2000 ™ ) as dependent variable included HbA 1c (Diamat ™ ) and HbF in the model ( r 2  = 0.946, p 1c (DCA 2000 ™ ). Partial correlation coefficient between HbA 1c (DCA 2000 ™ ) and HbF corrected for HbA 1c (Diamat ™ ) was 0.337 ( p  = 0.0012). Conclusions DCA 2000 ™ allowed measurements of HbA 1c rapidly and with precision adequate for clinical purposes. However, agreement with Diamat ™ results was comparatively weak with both constant as well as proportional biases. The 95% limits of agreement between Diamat ™ and DCA 2000 ™ fell within a range that significantly limited traceability between these two methods; therefore, the two methods should not be used interchangeably. Small but persistent elevations of HbF concentrations were identified as a significant cofactor, which may be relevant for limited traceability between the two methods.