Use of GHb (HbA(1c)) in screening for undiagnosed diabetes in che US population

OBJECTIVE - To evaluate the use of GHb as a screening test for undiagnosed diabetes (fasting plasma glucose greater than or equal to 7.0 mmol/l) in a representative sample of the U.S. population. RESEARCH DESIGN AND METHODS - The Third National Health and Nutrition Exami nation Sun-ey included national samples of non-Hispanic whites, non-Hispani c blacks, and Mexican Americans aged greater than or equal to 20 years. Of these subjects, 7,832 participated in a morning examination session, of whi ch 1,273 were excluded because of a previous diagnosis of diabetes, missing data, or fasting rime of <8 h before examination. Venous blood was obtaine d to measure fasting plasma glucose and GHb in the remaining 6,559 subjects . Received operating characteristic curve analysis was used To examine the sensitivity and specificity of GHb for detecting diabetes at increasing GHb cutoff levels. RESULTS - GHb demonstrated high sensitivity (83.4%) and specificity(83.4%) for detecting undiagnosed diabetes at a GHb cutoff of 1 SD above the normal mean. Moderate sensitivity (63.2%) and very high specificity (97.4%) were evident at a GHb cutoff of 2 SD above the normal mean, Sensitivity at this level ranged from 58.6% in the non-Hispanic white population to 83.6% in th e Mexican-American population; specificity ranged from 93.0% in the non-His panic black population to 98.3% in the non-Hispanic white population. CONCLUSIONS - GHb is a highly specific and convenient alternative to fastin g plasma glucose for diabetes screening. A GHb value of 2 SD above the norm al mean could identify a high proportion of individuals with undiagnosed di abetes who are at risk for developing diabetes complications.