The National Institutes of Health released the trial registry ClinicalTrials.gov in 2000 to increase public reporting and clinical trial transparency. This systematic review examined whether registered primary outcome specifications (POS; ie, definitions, timing, and analytic plans) in analgesic treatment trials correspond with published POS. Trials with accompanying publications (n = 87) were selected from the Repository of Registered Analgesic Clinical Trials (RReACT) database of all postherpetic neuralgia, diabetic peripheral neuropathy, and fibromyalgia clinical trials registered at ClinicalTrials.gov as of December 1, 2011. POS never matched precisely; discrepancies occurred in 79% of the registry-publication pairs (21% failed to register or publish primary outcomes [PO]). These percentages did not differ significantly between industry and non-industry-sponsored trials. Thirty percent of the trials contained unambiguous POS discrepancies (eg, omitting a registered PO from the publication, "demoting" a registered PO to a published secondary outcome), with a statistically significantly higher percentage of non-industry-sponsored than industry-sponsored trials containing unambiguous POS discrepancies. POS discrepancies due to ambiguous reporting included vaguely worded PO registration; or failing to report the timing of PO assessment, statistical analysis used for the PO, or method to address missing PO data. At best, POS discrepancies may be attributable to insufficient registry requirements, carelessness (eg, failing to report PO assessment timing), or difficulty uploading registry information. At worst, discrepancies could indicate investigator impropriety (eg, registering imprecise PO ["pain"], then publishing whichever pain assessment produced statistically significant results). Improvements in PO registration, as well as journal policies requiring consistency between registered and published PO descriptions, are needed.
Keywords: Analgesic medications; Clinical trials; Primary outcomes; Registry; Systematic review.
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