Forty years of randomised trials in the New Zealand Medical Journal

Abstract

Aim: To identify all randomised trials published in the New Zealand Medical Journal, to document the basic characteristics of these trials and to count the number that were detectable on medline.

Methods: All issues of the New Zealand Medical Journal between 1943 and 1995 were systematically hand-searched. All trials identified were characterised and compared against the trials identified using an optimal medline search strategy.

Results: The handsearch identified 152 randomised controlled trials, the first published in 1955. Half the trials recruited less than 34 participants and more than 90% were of pharmaceutical interventions. Only 18% of studies reported on the method of randomisation and 13% provided evidence that final analyses were conducted on an intention to treat basis. Fifty one percent of trials employed a placebo control group and 28% involved a crossover design. Since 1966, when Medline became available, 143 trials were published of which 89 (62%) were identified by the Medline search.

Conclusions: Two of the major difficulties that face those preparing systematic reviews were illustrated by this survey. First, important information on design and analysis is often missing from reports of trials. Second, a large proportion of published randomised trials are not identifiable on Medline. Standard formats for reporting the results of trials and inclusion of trials identified by hand-searching on the Cochrane Collaboration's International Register of Randomised Controlled Trials of Health Care will facilitate the future production of reliable systematic reviews.