Purpose: To investigate whether propensity score (ps) methods could reasonably be applied to estimate the treatment effect on mortality, based on a comparatively small sample of patients with severe cutaneous adverse reactions (SCAR) and who come from different countries where physicians prefer different treatment schemes.
Methods: Ps methods were applied to cope with confounding due to non-randomized treatment assignment for the analysis of the treatment data obtained in the case-control study EuroSCAR. For the study's purpose, the analysis focused on the comparison of the treatments: corticosteroids (STER) and supportive care only (SUPP).
Results: 206 French and German patients were treated either with SUPP or STER. Imbalances between treatment groups as well as between the countries were recognized. Concerning the balance between the treatment groups no ps model for the full cohort was satisfying. In addition, the inclusion of a variable for patient's country led to a separation of the patients by country. Thus, we developed ps models for each country separately and estimated the treatment effects (France: odds ratio (OR) 0.52, 95% confidence interval (CI) 0.09-3.10, Germany: OR 0.23, CI 0.06-0.92, Overall: OR 0.33 CI 0.11-1.04).
Conclusions: The application of the ps methods was successful and provided valuable information. We could confirm the findings of the original analysis which was based on standard logistic regression, especially concerning the necessity of a country-specific analysis. The observed country differences in the estimated treatment effects were less pronounced and thus seemed to be more reasonable than those of the past analysis.