Jeanne M. Rhea, David Koch, James Ritchie, Harsh V. Singh, Andrew N. Young, Tom Burgess, and Ross J. Molinaro (2013) Unintended Reporting of Misleading Hb A_1c Values When Using Assays Incapable of Detecting Hemoglobin Variants. Archives of Pathology & Laboratory Medicine: December 2013, Vol. 137, No. 12, pp. 1788-1791.

ORIGINAL ARTICLES

Unintended Reporting of Misleading Hb A_1c Values When Using Assays Incapable of Detecting Hemoglobin Variants

Jeanne M. Rhea , PhD; David Koch , PhD; James Ritchie , PhD; Harsh V. Singh , PhD; Andrew N. Young , MD, PhD; Tom Burgess ,PhD; Ross J. Molinaro , PhD, MT(ASCP)

From the Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia (Drs Rhea, Koch, Ritchie, Young, and Molinaro); the Department of Pathology and Laboratory Medicine, Grady Memorial Hospital, Atlanta, Georgia (Drs Koch and Young); the Department of Pathology, Hindu Rao Hospital, New Delhi, India (Dr Singh); and Laboratory Medicine, Quest Diagnostics, Atlanta, Georgia (Dr Burgess).

Context.—It is recommended that hemoglobin (Hb) A_1c (Hb A_1c) not be used to assess average glycemia in patients who have altered red blood cell life span.

Objective.—To investigate the frequency of reporting an Hb A_1c value for Hb variant samples that do not include Hb A.

Design.—Hb A_1c samples (n = 500) were procured and screened for Hb variants that may affect Hb A_1c interpretation (Hb SS, Hb SC, and Hb S–β-thalassemia). Five of each of these samples were tested by ion-exchange high-performance liquid chromatography, immunoturbidimetric assay, second-generation immunoturbidimetric assay, and affinity chromatography.

Results.—Eleven (2.2%) homozygous Hb SS, 6 (1.2%) Hb SC, and 5 (1.0%) Hb S–β-thalassemia samples were identified out of the 500 samples tested. Three of 4 instruments investigated in this study are known to not be plagued by analytic interference from these Hb variants but disturbingly reported Hb A_1c values in the absence of Hb A.

Conclusions.—The improved analytic specificity of Hb A_1c platforms has by and large eliminated interferences from the most common heterozygous Hb variants. A consequence, however, is the potential for unintended reporting of Hb A_1cresults in the presence of homozygous and compound heterozygous Hb variants that lack Hb A and the inability to distinguish those samples not recommended to be used for patient care. The ability to identify samples harboring Hb variants that preclude the utility of Hb A_1c may be beneficial in high prevalence populations.