Sensitivity and Specificity of Glycated Hemoglobin as a Diagnostic Test for Diabetes and Prediabetes in Arabs

Abstract

CONTEXT: Glycated hemoglobin (A1C) has been recommended by the American Diabetes Association for the diagnosis of diabetes and prediabetes. The diagnostic utility of A1C has not been evaluated in Arabs, a population at increased risk for developing diabetes. OBJECTIVE: Our objective was to examine the sensitivity and specificity of A1C for the diagnosis of diabetes and prediabetes in Arabs. DESIGN & SETTING: In this cross-sectional study, glucose tolerance was classified by the American Diabetes Association diagnostic criteria specified for A1C, fasting plasma glucose, and 75-g oral glucose tolerance test. PARTICIPANTS: A population-based representative sample of 482 randomly selected adult Arabs without known diabetes was studied. MAIN OUTCOME MEASURES: Sensitivity, specificity, and area under the receiver operating characteristic curve of A1C diagnostic cutpoints for diabetes and prediabetes were calculated. κ Coefficients were used to test for agreement between A1C categorization and glucose-based diagnoses. RESULTS: A1C testing correctly identified 5% of individuals diagnosed with diabetes by oral glucose tolerance test, 13% by fasting plasma glucose, and 41% by both criteria. A1C alone identified 14% of individuals diagnosed with impaired glucose tolerance, 9% with impaired fasting glucose, and 33% with both abnormalities. Sensitivity, specificity, and area under the receiver operating characteristic curve were 19% (16-23%), 100% (99-100%), and 77% (69-85%) for diabetes A1C cutpoint and 14% (11-17%), 91% (89-94%), and 57% (52-62%) for prediabetes A1C range. A1C cutpoint of 6.2% for diabetes and 5.1% for prediabetes yielded the highest accuracy but still missed 73% of those with diabetes and 31% with prediabetes. Agreement between A1C and diabetes (κ = 0.2835) or prediabetes (κ = 0.0530) was low. CONCLUSIONS: A1C-based criteria yield a high proportion of false-negative tests for diabetes and prediabetes in Arabs. SUMMARY: Racial/ethnic differences in A1C performance for diagnosis and prediction of diabetes exist. This paper examines its utility against glucose measurements in an at-risk Arab population.