A COMPARISON OF SUBJECTIVE AND OBJECTIVE MEASURES OF REDUCTION OF PSORIASIS WITH THE USE OF ULTRASOUND, REFLECTANCE COLORIMETRY, COMPUTERIZED VIDEO IMAGE-ANALYSIS, AND NITRIC-OXIDE PRODUCTION

Background: Studies of antipsoriatic therapy often rely on subjective scoring. Objective measures have been developed but have not previousl y been compared with subjective scoring. Objective: Our purpose was to compare subjective and objective measures of reduction of psoriasis w ith topical therapy. Methods: A 2-week, double-blind, left-to-right co mparative trial of betamethasone valerate against white soft paraffin was performed in 12 patients. The subjective scores were erythema, ele vation, scale, and a composite total. Objective measures were nitric o xide production measured by chemiluminescence; erythema reflectance; u ltrasound scan for thickness, scale, and echo-poor zone; and computeri zed image analysis of video images. Results: Subjective and objective measures had similar power to detect therapeutic effect. The subjectiv e measures showed greater variation and relatively overestimated impro vement. There was correlation between measures and estimates for area, redness, and thickness. Nitric oxide production was the most powerful objective measure. Conclusion: Thickness determined by ultrasound sca n and nitric oxide production are useful measures of reduction of psor iasis, which lend themselves to more powerful statistical tests than s ubjective interval data.