Participation of epidemiologists and/or biostatisticians and methodological quality of published controlled clinical trials

Study objective-This study assessed several methodological aspects related to the quality of published controlled clinical trials (CCTs) in relation t o the participation of an epidemiologist/biostatistician (E/B). Design-Handsearch of CCTs published in four medical leading journals for 19 93-1995. Methods-quality variables, abstracted from a review, were related to author s' specialties. Five hundred and ninety four CCTs were identified via a han d search. The department/unit membership was used to attribute authors' spe cialties. Of 594 CCTs identified, in 127 the authors' specialties could not be known, leaving 467 trials for analysis. Results-E/B participation occurred in 178 trials (38.1%). This participatio n was more frequent in multicentric, bigger, and in those trials describing any funding agency. These factors were controlled for in the analysis. E/B participation was positively associated with pre-study sample size estimat ion (OR = 1.5, 95% confidence intervals (CI) 1.0, 2.3), with reporting the dates for starting/ending the study (OR = 2.1, 95% CI 1.4, 3.3), with using an objectively assessed outcome (OR = 2.4, 95% CI 1.2, 4.6) and with the i ntention to treat principle (OR = 2.0, 95% CI 1.3, 3.0). The overall qualit y score was higher in trials where E/B participated. Conclusions-The results suggest that E/B improve the quality (at least of r eports) of clinical trials. Given that quality of research is frequently us ed to evaluate potential sources of heterogeneity between trials, these res ults are relevant for meta-analysis.