title: One in five laboratories using various hemoglobin A1c methods do not meet the criteria for optimal diabetes care management.
abstract: BACKGROUND
  We assessed the reference change value (RCV) of currently available hemoglobin A(1c) (HbA(1c)) laboratory assays, which is defined as the critical difference between two consecutive HbA(1c) measurements representing a significant change in health status.
  
  
  METHODS
  We examined the individual laboratory coefficients of variation (CVs) in the Dutch/Belgian quality scheme based on 24 lyophilized samples and calculated the RCV per laboratory (n = 220) and per assay method. In addition, two pooled whole blood samples were sent to the participating laboratories. The individual laboratory results were compared to the assigned value ± an allowable total error (TE(a)) of 6%.
  
  
  RESULTS
  At HbA(1c) values of 41.0 mmol/mol (5.9%-Diabetes Control and Complications Trial [DCCT]) and 61.8 mmol/mol (7.8%-DCCT), 99% and 98%, respectively, of the laboratories reported a value within a TE(a) limit of 6%. The analytical CV of the HbA(1c) method used in 78% of the laboratories is <2.4%. The mean RCV at an HbA(1c) value of 53 mmol/mol (7.0%-DCCT) for methods of Bio-Rad is 5.9 mmol/mol (0.59%-DCCT); for Arkray/Menarini, 4.3 mmol/mol (0.43%-DCCT); for Roche, 6.5 mmol/mol (0.65%-DCCT); for Tosoh, 3.3 mmol/mol (0.33%-DCCT); and for other methods, 6.3 mmol/mol (0.63%-DCCT).
  
  
  CONCLUSIONS
  The analytical performance of the majority of laboratory HbA(1c) methods is within the clinical requirements. However, based on the calculated RCV, 21.8% of the laboratories using different HbA(1c) methods are not able to distinguish an HbA(1c) result of 59 mmol/mol (7.5%-DCCT) from a previous HbA(1c) result of 53 mmol/mol (7.0%-DCCT). It can be presumed that differences in HbA(1c) results of 5 mmol/mol (0.5%-DCCT) do influence treatment decisions.
authors.affiliation: Department of Clinical Chemistry, Isala Klinieken, Zwolle, The Netherlands. w.b.lenters@isala.nl
authors.forename: Erna
authors.initials: E
authors.lastname: Lenters-Westra
authors.forename: Cas
authors.initials: C
authors.lastname: Weykamp
authors.forename: Roger K
authors.initials: RK
authors.lastname: Schindhelm
authors.forename: Carla
authors.initials: C
authors.lastname: Siebelder
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Bilo
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: Slingerland
mesh_terms: D001530:Belgium; D019411:Clinical Laboratory Techniques / Q000592:standards*; D003920:Diabetes Mellitus / Q000097:blood*; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D009426:Netherlands; D012016:Reference Values
chemical_list: D006442:Glycated Hemoglobin