O B J E C T I V E -To evaluate the use of GHb as a screening test for undiagnosed diabetes (fasting plasma glucose 7.0 mmol/l) in a re p resentative sample of the U.S. population. RESEARCH DESIGN AND METHODS -The Third National Health and NutritionExamination Survey included national samples of non-Hispanic whites, non-Hispanic blacks, and Mexican Americans aged 20 years. Of these subjects, 7,832 participated in a morn i n g examination session, of which 1,273 were excluded because of a previous diagnosis of diabetes, missing data, or fasting time of 8 h before examination. Venous blood was obtained to meas u re fasting plasma glucose and GHb in the remaining 6,559 subjects. Receiver operating characteristic curve analysis was used to examine the sensitivity and specificity of GHb for detecting diabetes at increasing GHb cutoff levels. R E S U LT S -GHb demonstrated high sensitivity (83.4%) and specificity (84.4%) 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 n o rmal mean. Sensitivity at this level ranged from 58.6% in the non-Hispanic white population to 83.6% in the Mexican-American population; specificity ranged from 93.0% in the nonHispanic black population to 98.3% in the non-Hispanic white population.C O N C L U S I O N S -GHb is a highly specific and convenient alternative to fasting plasma glucose for diabetes screening. A GHb value of 2 SD above the normal mean could identify a high pro p o rtion of individuals with undiagnosed diabetes who are at risk for developing diabetes complications.

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BACKGROUND:The correlation between hemoglobin A 1c (Hb A 1c ) and risk for complications in diabetic patients heightens the need to measure Hb A 1c with accuracy. We evaluated the current performance for measuring Hb A 1c in the Asian and Pacific region by examining data submitted by laboratories participating in the Taiwan proficiency-testing program.