Improving the Accuracy of Hemoglobin A1c: Your Help Is Needed

Abstract

Clinical laboratory personnel are important members of the diabetes treatment team, from the technical staff, to the supervisor, to the pathologist. The technicians and technologists measure glucose, hemoglobin A 1c (A1c), lipids, microalbumin, and liver function tests for diabetic patients to help those patients to decrease the risk of chronic complications. The laboratory staff and supervisors monitor quality control with a critical eye. The laboratory management brings in better instrumentation and methodology as soon as it is feasible. Questionable laboratory results are investigated and corrected. Quality assurance is not just a catchphrase, it is a way of life. So it is a cause for concern to all laboratory professionals that A1c results may be inaccurate, yet reported, in patients who have variant hemoglobins. The nature of the A1c inaccuracy, whether it is a spurious increase or decrease, is specific to the method used and to the variant hemoglobin (eg, HbS, HbC, HbE, HbF). An analysis of the capabilities of available methods is listed at a Web site maintained by the National Glycohemoglobin Standardization Program (NGSP). 1 The 2 major types of testing currently in use are high-performance liquid chromatography (HPLC) and immunoassay. High-performance liquid chromatography has an advantage in that the latest generation of analyzers can resolve and identify several forms of hemoglobin, including most variants, and it provides a chromatogram that shows peaks where the forms have been resolved. High-performance liquid chromatography analyzers also provide quantitation of those peaks. Immunoassay accuracy may be affected by some variant hemoglobins, but there is no visual interpretation of the results other than a number to aid the laboratory professional in evaluating accuracy. Immunoassay analyzers are simpler to use and, as a result, are used as point-of-care tests (POCT) in physicians’ offices. This can be problematic as physicians may be unaware that a particular diabetic patient has a hemoglobinopathy. Hemoglobin electrophoresis is not a recommended laboratory test for a new diabetic, according to the American Diabetes Association (ADA) Standards of Medical Care. 2 Moreover, diabetic individuals may not be aware that they have a hemoglobinopathy or that a known hemoglobin variant can affect their A1c results. Diabetic patients with hemoglobinopathies may receive inaccurate A1c results several times before the error and cause is discovered. This is a serious quality issue for all laboratory professionals. This report will discuss this system error in A1c testing and recommend a method to eliminate it. The recommendation will ask you, the reader, to make it happen. Collective data on laboratory practices provided by you will be used to determine testing and reporting practices and be used