Reliability assessment and validation of the postacne hyperpigmentation index (PAHPI), a new instrument to measure postinflammatory hyperpigmentation from acne vulgaris

Background: There are no validated outcome measures for postinflammatory hyperpigmentation (PIH). Objective: We sought to determine the reliability and validity of an outcome measure for PIH after acne in patients with skin of color. Methods: A postacne hyperpigmentation index (PAHPI) was developed. Six raters scored 21 patients with PIH twice. Reliability was determined within and between raters, whereas validity was evaluated by comparing scores with severity ranking by an independent dermatologist. The pigment intensity scores were compared with the melanin index of each patient using a narrowband reflectance spectrophotometer. A quality-of-life score (Skindex-29) was also compared with PAHPI scores. Results: Total PAHPI scores showed good reliability within and between raters and were valid when compared with clinical severity and melanin indices. Good correlation was achieved between the total PAHPI score and the emotion subscale of the Skindex-29. Limitations: Generalizability of results is limited to African American females. Conclusion: The PAHPI shows good reliability and validity when scored on patients with PIH from acne vulgaris. The PAHPI also correlates well with the emotional impact of PIH as measured by the Skindex-29. Future studies should assess the ability of the PAHPI to change with improvement of PIH from acne after treatment.