Reliability assessment and validation of the Melasma Area and Severity Index (MASI) and a new modified MASI scoring method.

BACKGROUND: The Melasma Area and Severity Index (MASI), the most commonly used outcome measure for melasma, has not been validated.

OBJECTIVE: We sought to determine the reliability and validity of the MASI.

METHODS: After standardized training, 6 raters independently rated 21 patients with mild to severe melasma once daily over a period of 2 days to determine intrarater and interrater reliability. Validation was performed by comparing the MASI with the melasma severity scale. The darkness component of the MASI was validated by comparing it with the difference between mexameter scores for affected versus adjacent normal-appearing skin. The area component of the MASI was validated by comparing it with the area of each section of the face determined by computer-based measurement software.

RESULTS: The MASI score showed good reliability within and between raters and was found to be valid when compared with the melasma severity scale, mexameter scores, and area measurements. Homogeneity assessment by raters showed the least agreement and can be removed from the MASI score without any loss of reliability.

LIMITATIONS: Patients were limited to Hispanic, African, and Asian backgrounds.

CONCLUSION: The MASI is a reliable measure of melasma severity. Area of involvement and darkness are sufficient for accurate measurement of the severity of melasma and homogeneity can be eliminated.