A quantitative scale of acanthosis nigricans

OBJECTIVE - To develop and validate a scale for acanthosis nigricans (AN). RESEARCH DESIGN AND METHODS- Subjects were participants from the San Antoni o Family Diabetes Study and the San Antonio Family Heart Study. A total of 406 subjects were independently examined for AN by at least two observers. Five locations were examined the neck, axilla, elbows, knuckles, and knees. Interobserver concordance and kappa statistics were calculated to determin e replicability of the scale. Comparisons of diabetes-related risk factors by AN score were also calculated. RESULTS - Only the neck had consistently high kappa statistics, and thus, o ther locations were excluded from further analyses. Elevated AN was strongl y associated with elevated fasting insulin and BMI in both diabetic and non diabetic subjects. Elevated AN was also strongly associated with elevated f asting glucose, systolic blood pressure, and diastolic blood pressure, and with decreased HDL in nondiabetic subjects. In diabetic subjects, elevated AN was associated with elevated total cholesterol. CONCLUSIONS - We have developed a scale for AN that is easy to use, has hig h interobserver reliability in Mexican Americans, and correlates well with fasting insulin and BMI. This scale will permit longitudinal and cross-sect ional evaluation of AN and will, permit the evaluation of AN as a trait in genetic studies.