A1C Usefulness in Detecting New Diabetes Limited
However, for those with higher A1C starting out, annual screening may be a reasonable strategy
FRIDAY, Sept. 3 (HealthDay News) -- Testing serum A1C levels is less sensitive for detecting individuals at risk for diabetes than other tests, but can be used for ongoing screening and diagnosis in those whose baseline A1C is already elevated, according to research published in the September issue of Diabetes Care.
Carlos Lorenzo, M.D., of the University of Texas Health Science Center in San Antonio, and colleagues compared A1C tests, impaired fasting glucose (IFG) tests, and impaired glucose tolerance (IGT) tests for 855 participants in the Insulin Resistance Atherosclerosis Study. A1C between 5.7 and 6.4 percent, a range for diabetes risk, detected 23.6 percent of at-risk individuals, while IFG and IGT identified 69.1 and 59.5 percent, respectively.
In a second study, Osamu Takahashi, M.D., of the University of Oxford in the United Kingdom, and colleagues studied 16,313 healthy Japanese adults who were not taking glucose-lowering medications. Annual A1C tests were performed from 2005 through 2008. For those with A1C less than 5.0 percent at baseline, cumulative diabetes incidence at three years was 0.05 percent; among those with 5.0 to 5.4 percent A1C, incidence at three years was 0.05 percent; it was 1.2 percent for those with 5.5 to 5.9 percent A1C and 20 percent for those with 6.0 to 6.4 percent A1C.
"In conclusion, for the purpose of detecting new cases of diabetes, in those with an initial A1C <6.0 percent, rescreening at intervals shorter than three years identifies few individuals (approximately ≤1 percent) with an A1C ≥6.5 percent. At A1C ≥6 percent, rescreening even at a one-year interval would be [a] reasonable strategy to identify disease," Takahashi and colleagues conclude.