This tool is mainly used in research for measuring severity in patients who have melasma (chloasma, pregnancy mask).
It would be useful in the measurement of the melasma before and after a treatment for example.
Its measurement relies on the measurement in 4 areas:
- (F) forehead which accounts for 30% of the score
- (RMR) right and (LMR) left malar region which each account for 30% of the score
- (M) chin which accounts for 10% of the score
The area (A) of melasma involvement is graded from 0 to 6:
- 0 = no involvement
- 1 = less than 10% involvement
- 2 = 10% to 29% involvement
- 3 = 30% to 49% involvement
- 4 = 50% to 69% involvement
- 5 = 70% to 89% involvement
- 6 = 90% to 100% involvement
The degree of pigmentation (P) and homogeneity (H) graded from 0 to 4:
- 0 = absent
- 1 = slight
- 2 = mild
- 3= marked
- 4 = maximum
MASI score = 0.3 A(F) [P(F) + H(F)] + 0.3 A(RMR) [P(RMR) + H(RMR)] + 0.3 A(LMR) [P(LMR) + H(LMR)] + 0.1 A(M) [P (M) + H (M)].
This measurement is highly subjective and different values can be found in the same patient at the same time !
It is subjective not only because each parameter is subjective but also because it is so complicated that physicians will calculate an approximate score based on impressions.
It could be used clinically but for research a colorimeter would be a better option, especially if more precise and reproductible measurements are sought.
Dr Christophe HSU – dermatologist. Geneva, Switzerland
Source of Information: Alrawashdeh B. Melasma Update. Dubai World Dermatology & Laser Conference & Exhibition – Dubai Derma 13 – Dubai, United Arab Emirates (UAE)