Endocrine Abstracts

Objectives: To estimate the prevalence of acanthosis nigricans (AN) in a cohort of obese subjects and to assess the validity of AN as an indicator of insulin resistance

Methods: 88 healthy obese subjects were assessed clinically for severity of AN scored according to Burke's Scale1. Neck and axilla severity scores (NASS) were discriminative, easy to access in a clinical setting and hence used in the analysis. Insulin resistance was assessed by Homeostasis Model Assessment (HOMA) from fasting glucose (glucose oxidase method) and insulin (Microparticle Enzyme Immunoassay -cross reactivity with pro-insulin <0.005%). Receiver operating curves (ROCs) were used to evaluate the accuracy of AN as a diagnostic indicator of insulin resistance. The Local Research Ethics Committee approved the protocol and all patients gave informed consent.

Results: 48 subjects (55%) had evidence of AN. ROC curves were plotted for the various cut-offs of NASS scores; the best was at the Grade 4 level (AUC=0.73; P=0.004;CI=0.57 to 0.88). Sensitivity was 45%; specificity, 97%; positive predictive value, 82%; likelihood ratio, 15; accuracy, 85%.

Conclusions: Acanthosis nigricans is a useful diagnostic marker of insulin resistance. It is easy to diagnose and should be part of the clinical examination of the obese patient.

1Burke JP, Hale DE, Hazuda HP et al. A quantitative scale for acanthosis nigricans. Diab Care: 22;1655-1658, 1999.