Differences in efficacy between intention-to-treat and per-protocol analyses for patients with psoriasis vulgaris and atopic dermatitis: clinical and pharmacoeconomic implications.

Abstract

Pharmacoeconomic outcome research is based on three criteria: (i) evaluation of objective therapeutic effects; (ii) quality of life; and (iii) treatment costs. Evaluation of therapeutic effect is mainly based on the results of clinical trials using objective clinical measures, e.g: Psoriasis Area and Severity Index (PASI) (score for psoriasis vulgaris) and the Severity Scoring of Atopic Dermatitis (SCORAD) (score for atopic dermatitis). In most studies, only results for a treatment-optimized subpopulation (patients treated according to the protocol) are presented in publications. The relevance of such data for daily routine therapy is doubtful. Our purpose was to investigate the expected loss of effectiveness of switching from a clinical trial to daily routine therapy for the synchronous application of narrow-band ultraviolet (UV) B phototherapy (311 nm) and bathing in 10% Dead Sea salt solution (synchronous balneophototherapy) for patients with psoriasis vulgaris and atopic dermatitis. We conducted a multicentre, uncontrolled observational study of outpatients. To achieve data for 'clinical trial' and 'daily routine' situations, two populations were compared: (i) all patients strictly treated according to the protocol (ATP) with no protocol deviations (data published in clinical trials), and (ii) all patients participating in the study who received active treatment at least once, despite treatment irregularities, non-compliance, early withdrawal or other protocol violations [intention-to-treat-population (ITT), model for 'daily routine']. A total of 2526 patients were included in the ITT analysis for psoriasis vulgaris (n = 487 for atopic dermatitis), of which 818 patients could be analysed according to protocol (n = 104 for atopic dermatitis). Striking differences in the therapeutic effect between both groups (ITT and ATP) were found using relative PASI and SCORAD score improvement: 11% (57% 'daily routine' vs. 68% in 'clinical trial') for psoriasis vulgaris and 16% (39% 'daily routine' vs. 55% 'clinical trial') for atopic dermatitis. The main reasons for excluding patients from the 'clinical trial' group were early study withdrawal in 29% (atopic dermatitis, 47%) of patients and fewer treatments per week than planned in the protocol in 24% (atopic dermatitis, 52%). Our data clearly indicate that for the prediction of the therapeutic effect for daily routine therapy the ITT data appear to be more relevant than the ATP results (i.e. those presented in clinical trials). Although these data are only a first step for evaluating the 'real' therapeutic effect of a treatment modality in daily routine, they seem to support the requirements for ITT analyses in efficacy studies and demonstrate the necessity of ITT data for pharmacoeconomic evaluation.