To the Editor.
— Imperiale and Petrulis report a meta-analysis of the use of low-dose aspirin to prevent pregnancy-induced hypertensive disease.1 Despite a review of the English-language literature, they are apparently unaware of a similar meta-analysis first published by Collins in May 1988 and regularly updated subsequently.2,3 Unlike Imperiale and Petrulis, Collins excluded all nonrandomized studies since such studies may introduce a bias in the assessment of treatment. Similarly, because of concerns about the selection biases that might arise by reviewing only the published data, Collins included data from unpublished studies as well as seeking information from investigators about relevant outcome measures that had not been reported. Thus, 13 studies contribute to his latest analysis including the results of the largest trial the results of which were presented publicly in January 1990 and published recently.4We would commend databases such as the Oxford Database of Clinical Trials3
Redman CWG, Lindheimer MD. Low-Dose Aspirin to Prevent Pregnancy-Induced Hypertensive Disease. JAMA. 1991;266(22):3127. doi:10.1001/jama.1991.03470220042016