Evaluation of efficacy of therapy for psoriasis : methodological issues

To the Editor

We read with interest the recent article on the efficacy of sulfasalazine versus methotrexate in the treatment of psoriasis.[1] The authors have concluded that the efficacy of sulfasalazine was comparable to methotrexate, and established drug for treating severe psoriasis. However, a few methodological issues relating to the study need to be addressed.

In each treatment group 15 patients were included. This number does not appear to be adequate for evaluation of antipsoriatic property of a medication.[2] Inadequate number of patients are likely to show no difference between two treatments when a real difference exists. Further, the assessment of efficacy was made by grading erythema, scaling, and thickness of the lesions without taking into account different regions of the body and their extent of involvement. It would have been more appropriate if an accepted method of grading psoriasis, e.g. Psoriasis Area and Severity Index,[3] was used to enable us to arrive at meaningful conclusions. Further more, the patients in the methotrexate group received 7.5 mg of the drug per week. As the antipsoriatic dose of methotrexate is 0.2 to 0.4 mg per kg body weight per weak,[4] it appears that the patients received a suboptimal dose. It is highly likely that with an optimum dose the response would have been much better with methotrexate.

Though the authors have provided interesting preliminary findings, in view of the foregoing discussion, it appears that the achievement of the objective of the study[1] would require further work.