Abstract
BACKGROUND: Randomised clinical trials are pivotal in guiding clinical practice. Trials with surrogate outcomes and industry sponsorship might be less reliable than those with hard outcomes and independent sponsorship. The types of interventions evaluated in randomised clinical trials might not reflect the diversity of those employed in clinical practice. METHODS: We assessed the types of primary outcome, types of intervention and sponsorship of 360 randomised clinical trials evaluating 416 interventions, published in seven major general medical journals and 10 speciality medical journals in five clinical disciplines. RESULTS: Primary outcomes were surrogate in 223/360 (62%) trials. Neither type of journal nor source of sponsorship was associated with type of primary outcome. Among the interventions evaluated, 233/416 (56%) were drugs, 17/416 (4%) devices and 49/416 (12%) procedures. The majority of trials were non-industry funded (220/360, 61%). Trials of drug interventions and those with industry sponsorship were more common in specialty than general journals (68% vs 48% and 55% vs 25%, respectively). Industry sponsorship was not associated with results for the primary outcome but was strongly associated with trials of drugs and devices. Within the groups of both general and speciality journals, there were wide ranges in the prevalence of industry funding (7-63% and 37-70%, respectively), but in all cases the prevalence of hard primary outcomes was <40%. CONCLUSIONS: Most randomised clinical trials published in influential journals reported surrogate primary outcomes and assessed drug interventions. Trials that evaluated devices and procedures were infrequently published, despite the prominence of each type of intervention in clinical practice. Industry funding was more common for trials published in specialty than general journals but was not associated with more positive results for primary outcomes or with a greater preponderance of surrogate outcomes.