Abstract
Data on treatment estimation from patients (n = 382) and their physicians (n = 358 guesses) in an RCT investigating the role of adjunct prednisone for community-acquired pneumonia in a tertiary care setting were analysed. At discharge, patients and their physicians had to guess whether they had been assigned to the prednisone or to the placebo group. The alternative possibility was “uncertain”. Percentages and confidence intervals (CIs) were calculated for the proportion of patients guessing correctly. Chance finding was defined as having 50% or less correct guesses. To test for predictors for prednisone treatment guess, a mixed effects logistic regression model was performed. In the prednisone group, 28.9% (55/190; 95% CI 22.6–36.0%) of the patients made a correct guess and the majority (61.6%, 117/190) was uncertain. In the placebo group, 13.0% (25/192; 95% CI 8.8–18.8%) guessed correctly, with the majority being uncertain (69.8%, 134/192). Physicians guessed correctly in 48.3% (87/180, 95% CI 40.8–55.9%) of cases in the prednisone group and in 66.3% (118/178, 95% CI 58.8–73.2%) of cases in the placebo group, which was above chance for the placebo group. The physicians were uncertain in 21.7% (39/180) of cases in the prednisone group, and in 15.2% (27/178) of cases in the placebo group. Significant predictors for guessing prednisone were the occurrence of hyperglycaemia (odds ratio [OR] 3.77, 95% CI 2.39–5.95; p<0.001) and a shorter time to clinical stability (OR 0.95, 95% CI 0.91–0.99; p = 0.02). We confirmed that patient blinding was achieved in this study. Physicians made correct guesses more often than patients. Treatment estimation by both patients and physicians was led not only by the expectations of treatment effects of the study drug but also by known side effects of prednisone. Trial registration no.: NCT00973154  .
Highlights
Randomised, placebo-controlled, double-blind studies (RCTs) have emerged as a gold standard in evaluating the effects of new drug treatments, but the internal validity of the process of double blinding has become a target of criticism [1]
Physicians guessed correctly in 48.3% (87/180, 95% confidence intervals (CIs) 40.8–55.9%) of cases in the prednisone group and in 66.3% (118/178, 95% CI 58.8–73.2%) of cases in the placebo group, which was above chance for the placebo group
Significant predictors for guessing prednisone were the occurrence of hyperglycaemia and a shorter time to clinical stability
Summary
Randomised, placebo-controlled, double-blind studies (RCTs) have emerged as a gold standard in evaluating the effects of new drug treatments, but the internal validity of the process of double blinding has become a target of criticism [1]. Two studies evaluating the effects of two antidepressant drugs compared with placebo showed that the majority of patients and physicians were able to distinguish active drug from placebo [2, 3] In these studies, the more certain the patients were about their guess, the higher was their probability of a correct guess. Even more striking is the effect of an antidepressant drug in chronic pain management: Pretreatment expectations of pain relief influenced the extent of pain relief in patients assigned to the intervention group. This was not observed in the placebo group, suggesting an effect beyond placebo [6]
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