The Adapted Classification of Male Pattern Hair Loss Improves Reliability

Abstract

Background: The Hamilton-Norwood classification (HNC) is used to assess the severity of pattern hair loss (PHL). Conflicting associations between PHL and cardiovascular disease (CVD) have been reported from studies that used different methods to assess alopecia severity. No classification including the HNC has been validated for population studies. We aimed to simplify the HNC, produce the adapted HNC and test its reliability for use in population studies. Methods: Identifying vertex alopecia as distinct allowed for a simpler alignment of alopecia figures where scores 4V and 5V in the adapted HNC replace IV and V in the original HNC. The two classifications were to be used by twelve of our staff (secretaries, nurses, dermatology trainees and dermatologists) to evaluate 16 men with PHL. Observer agreement was estimated using intraclass correlation coefficient (ICC) and a percentage method duplicated from the recent basic and specific (BASP) classification. Results: The ICC improved with the adapted HNC when assessed by both the nurses/secretaries (from 0.47 to 0.61) and dermatology residents/consultants (from 0.68 to 0.76). Agreement using the BASP percentage method for dermatologists was 62–69% for the original and 93–100% for the adapted HNC. Conclusions: The adapted HNC increased reliability at various staff levels, making it suitable for epidemiological studies; its use in future studies could help elucidate the association between PHL and CVD.