title: Epidemiologic studies of adverse effects of anti-retroviral drugs: how well is statistical power reported.
abstract: OBJECTIVE
  To determine whether there is a difference in average statistical power between pharmacoepidemiologic studies of anti-retroviral adverse drug effects (ADEs) sponsored by for-profit versus non-profit organizations.
  
  
  METHODS
  We studied all published pharmacoepidemiologic studies of ADEs associated with the 15 anti-retroviral drugs approved through the end of 1999. A priori, the primary outcome was the power of each study to detect a clinically important difference in the risk for an adverse effect among patients exposed to the study drug(s). We could not evaluate this outcome because of the infrequent reporting of power calculations. We instead report the distribution of studies across a 5-tiered measure of adequacy of reporting of statistical power, as well as the sponsorship of these studies.
  
  
  RESULTS
  Of 48 studies meeting our inclusion criteria, only 1 (2%) reported either a completed, a priori power calculation or sufficient details for readers to calculate the power to detect a pre-defined, clinically important effect. Thirty-five studies (73%) reported the minimum information required for sophisticated readers to determine the power to detect an event rate of interest to them; 6 additional studies (13%) reported confidence intervals around at least one summary effect measure and 6 (13%) provided no indication of power or uncertainty. Of the 41 studies for which sponsorship was determined, only 3 (7%) were sponsored by for-profit organizations.
  
  
  CONCLUSIONS
  The poor reporting of statistical power in this sample suggests a need for guidelines to improve the reporting of pharmacoepidemiologic studies of ADEs. Future research is needed to determine whether the observed paucity of industry-sponsored observational studies of anti-retroviral ADEs extends to other clinical areas, and if so, to identify the causes of this phenomenon.
authors.affiliation: Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Halpern
authors.forename: Todd D
authors.initials: TD
authors.lastname: Barton
authors.forename: Robert
authors.initials: R
authors.lastname: Gross
authors.forename: Sean
authors.initials: S
authors.lastname: Hennessy
authors.forename: Jesse A
authors.initials: JA
authors.lastname: Berlin
authors.forename: Brian L
authors.initials: BL
authors.lastname: Strom
mesh_terms: D016907:Adverse Drug Reaction Reporting Systems / Q000706:statistics & numerical data; D044966:Anti-Retroviral Agents / Q000009:adverse effects* / Q000627:therapeutic use; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D006801:Humans; D009935:Organizational Affiliation / Q000191:economics / Q000706:statistics & numerical data; D017891:Pharmacoepidemiology / Q000379:methods* / Q000706:statistics & numerical data; D012107:Research Design; D012109:Research Support as Topic / Q000191:economics / Q000706:statistics & numerical data; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D044966:Anti-Retroviral Agents