Grading Acanthosis Nigricans Using a Smartphone and Color Analysis: A Novel Noninvasive Method to Screen for Impaired Glucose Tolerance and Type 2 Diabetes

Abstract

Objective The objective of this study was to develop ANcam, a novel method for identifying acanthosis nigricans (AN) using a smartphone camera and computer-aided color analysis for noninvasive screening of people with impaired glucose tolerance (IGT). Research Design and Methods Adult and juvenile participants with or without diagnosed type 2 diabetes were recruited in Trinidad and Tobago. After obtaining informed consent, participants’ history, demographics, anthropometrics, and A1C were collected and recorded. Three subject matter experts independently graded pictures of the posterior neck and upper back using the ANcam smartphone application and Burke methods. A correlation matrix investigated 25 color channels for association with hyperpigmentation, and the diagnostic thresholds were determined with a receiver operating characteristic curve analysis. Results For the 227 participants with captured images and A1C values, the cyan/magenta/yellow/black (CMYK) model color channel CMYK_K was best correlated with IGT at an A1C cutoff of 5.7% (39 mmol/mol) (R = 0.45, P <0.001). With high predictive accuracy (area under the curve = 0.854), the cutoff of 7.67 CMYK_K units was chosen, with a sensitivity of 81.1% and a specificity of 70.3%. ANcam had low interrater variance (F = 1.99, P = 0.137) compared with Burke grading (F = 105.71, P <0.001). ANcam detected hyperpigmentation on the neck at double the self-reported frequency. Elevated BMI was 2.9 (95% CI 1.9–4.3) times more likely, elevated blood pressure was 1.7 (95% CI 1.2–2.4) times more likely, and greater waist-to-hip ratio was 2.3 (95% CI 1.4–3.6) times more likely with AN present. Conclusion ANcam offers a sensitive, reproducible, and user-friendly IGT screening tool to any smartphone user that performs well with most skin tones and lighting conditions.