- PASI calculating: the area and intensity of psoriasis: PASI=0, 1 (E+D+I) Ah+0, 2 (E+D+I) Au+0, 3 (E+D+I) At+ 0, 4 (E+D+I) Al In which: + Area: 0, 1 + 0, 2 + 0, 3 + 0, 4 = 1 To be specific: Head: 0, 1, upper limbs: 0, 2, trunk: 0, 3, lower limbs: 0, 4 + Intensity: Erythema (E); Desquamation (D); Infitration (I).