TUESDAY, June 19 (HealthDay News) -- For postpartum women who have had gestational diabetes mellitus (GDM), the hemoglobin A1c (A1C) test criteria alone or in combination with fasting glucose test criteria does not provide sensitive and specific diagnosis of abnormal carbohydrate metabolism compared with the gold-standard oral glucose tolerance test (OGTT), according to a study published online June 11 in Diabetes Care.

María José Picón, M.D., Ph.D., of the Virgen de la Victoria University Hospital in Malaga, Spain, and colleagues measured the sensitivity and positive predictive value (PPV) of the A1C test, with or without the fasting glucose test, compared with the OGTT in 231 postpartum women with prior GDM one year after delivery.

The researchers found that, based on the OGTT, A1C test, fasting glucose test, and A1C-fasting glucose test criteria, the prevalence of abnormal carbohydrate metabolism was 45.89, 19.05, 38.10, and 46.75 percent, respectively. Compared with the OGTT, the A1C test had a sensitivity and PPV of 22.64 and 54.55 percent, respectively; while the fasting glucose criterion had a sensitivity and PPV of 83.02 and 100 percent, respectively. Using both together, the sensitivity and PPV were 83.02 and 81.48 percent, respectively; and these criteria classified 18 women with normal carbohydrate metabolism as having abnormal carbohydrate metabolism.

"In summary, the A1C test significantly underdiagnosed carbohydrate metabolism disorders in women who had had GDM," the authors write.

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