1330-P: Glucose-6-Phosphate Dehydrogenase Deficiency Masks the Diagnosis of Abnormal Glucose Tolerance by A1C—The Africans in America Study

Introduction and Objective: Genetic association studies report lower A1C levels with G6PD deficiency (G6PD-D). A1C is used as a diagnostic test for abnormal glucose tolerance (AbnlGT), a summary term for diabetes and prediabetes. It is critical to assess the clinical impact of G6PD-D on the diagnostic efficacy of A1C in populations in whom deficiency variants are common and risk of AbnlGT is high, such as Africans. G6PD-D is X-linked and caused primarily by the G6PD A- haplotype in Africa. G6PD-D can be assessed by either genotyping or clinical assay. We determined: 1) the ability of A1C to detect AbnlGT by G6PD-D status; 2) concordance of genotyping and the clinical assay in 506 African-born Blacks enrolled in the Africans in America study (men: 61% (308/506). Methods: AbnlGT was diagnosed by the OGTT. G6PD-D was assessed by genotype only (n=263), genotype and assay (n=188) or assay only (n=55). G6PD-D clinical assay used qualitative visual fluorescence screening in whole blood. A1C ≥5.7% was the threshold for AbnlGT. Results: G6PD-D status was indeterminant in 13 women who were heterozygous for G6PD A- and did not have the assay. In the remaining 493 participants, AbnlGT occurred in 41% (201/493) and G6PD-D in 10% (51/493). G6PD-D prevalence in men and women were: 14% (43/308) v 4% (8/185) P<.001. A1C levels with and without G6PD-D were: 4.6 ± 0.5, (range 3.1 - 5.6) v 5.5 ± 0.6 (range 4.2 - 11.3), P<.001). With G6PD-D, A1C sensitivity and specificity for AbnlGT detection were: 0% (0/16) and 100% (35/35), resp. Without G6PD-D, A1C sensitivity and specificity were: 50% (93/185) and 79% (202/257), resp. Participants with both genotyping and the assay (n=188), concordance for G6PD-D detection was 100%. Conclusion: G6PD-D lowered A1C levels by 0.9%. These falsely low A1C levels could lead to late diagnosis of AbnlGT and complications. Overall, as the assay can detect deficiency in women heterozygous for G6PD A-, the assay for G6PD was more informative than genotyping. Disclosure A.R. Bentley: None. K. Ntabadde: None. K. Balahali: None. K. Ekoru: None. C. DuBose: None. D.B. Sacks: Other Relationship; Sebia, Trinity. A.A. Adeyemo: None. C.N. Rotimi: None. A.E. Sumner: None.