Reliability assessment and validation of the post-acne hyperpigmentation index (PAHPI) in a population from Sub-Saharan Africa in Senegal

Abstract

Background: A post-acne hyperpigmentation index (PAHPI) has been developed in the United States to better compare therapeutic modalities. Our aim in this study was to validate the PAHPI score in patients with skin type VI from sub-Saharan Africa.

Patients and methods: The study was conducted in Dakar, Senegal. Twenty-one patients with Fitzpatrick skin type VI, aged 17 to 55 years, presenting hyperpigmentation secondary to acne were included. Ongoing use of skin bleaching products or acne treatments was allowed. Four trained dermatologists rated the patients using the PAHPI. A narrow-band reflectance spectrophotometer (Mexameter MX-18, Cologne, Germany) was used to measure the degree of pigmentation of involved and adjacent skin on 6 representative facial lesions.

Results: The average inter-rater reliability (weighted Kappa) showed substantial agreement for intensity (0.67), moderate agreement for number (0.53) and fair agreement for lesion size (0.28). Inter-rater reliability for the total PAHPI was excellent for both day 1 and day 2 (interclass correlation coefficient of 0.87 and 0.85, respectively; P<0.0001). Intra-rater reliability for total PAHPI ranged from 0.83 to 0.93 (P<0.0001). PAHPI scoring thus demonstrated excellent reliability both between and within raters. The association was moderate to substantial for all raters on both days (range for rho on day 1: 0.531 to 0.815; range for rho on day 2: 0.448 0.762). The correlations between the Mexameter (Courage and Khazaka) measurements and PAHPI scores showed moderate to substantial agreement.

Conclusion: Although tested primarily in African American women to date, PAHPI is also valid for patients from sub-Saharan Africa.

Keywords: Acne; Hyperpigmentation; PAHPI; Post-acne hyperpigmentation index.