Predicting the risk of postinflammatory hyperpigmentation: The palmar creases pigmentation scale

Abstract Background Postinflammatory hyperpigmentation (PIH) may affect any skin type but has been linked more often to darker skin. While propensity to hyperpigmentation has not been fully elucidated, there may be a direct correlation to one's palmar crease pigmentation. Objective The aim of this study is to validate the reliable use of a palmar creases pigmentation (PCP) scale, and its accuracy in predicting the risk of PIH. Methods A prospective, comparative, and blinded study was conducted through photo‐numeric analysis of 126 photographs of pairs of palms. We utilized a 4‐point visual scale based on the level of contrast between palmar crease pigment and that of the surrounding skin. Score 0 indicated no difference, score 1 referred to a low difference, score 2 meant a moderate difference, and score 3 related to a high difference. Scores were subdivided based on the risk of PIH. Scores 0‐1 are low risk and scores 2‐3 are high risk . A panel of 8 medical experts independently evaluated and re‐evaluated the photographs that were shown in a random order. Results A significant degree of inter‐rater reliability was found at both evaluation visits, with an intra‐class correlation coefficient (ICC) = 0.908, P <.001, at the first evaluation and an ICC = 0.924, P <.001, at the second evaluation, demonstrating a validity of the scale. Global Fleiss kappa for intra‐rater reliability for all physicians was 0.514. Conclusion The PCP scale can be effectively used by any physician to predict hyperpigmentation risk.