Ioannidis 1998.

Study characteristics
Methods	Multi‐centre trials groups in HIV sponsored by the National Institute of Health (NIH) conducted between 1986 and 1996. Publication status was obtained from the trial registry that sponsored the trial.
Data	66 multi‐centre AIDS trials.
Comparisons	Publication status of trials with positive findings compared with those with negative findings. Trials were classified as either positive if P < 0.05 (or favoured the experimental arm of the trial), or as negative if the difference had a P value above 0.05 (or favoured the control arm of the trial).
Outcomes	Trials with positive results were more likely to be published than those with negative results. Total published = 36/66 (54%) Positive = 20/27 (74%) Negative = 16/39 (41%) Other variables assessed included time to publication and sample size.
Notes	109 trials were identified of which 66 were included in the analysis. Reasons for exclusion were: closed as failed to accrue (n = 8); still open to accrual (n = 25); still open to follow up (n = 10).
Risk of bias
Item	Authors' judgement	Support for judgement
Inception cohort?	Yes	"All efficacy clinical trials conducted from 1986 until 1996 by the AIDS Clinical Trial Group (ACTG) and by the Terry Beirn Community Programs for Clinical Research on AIDS (CPCRA) were considered in the analysis." (page 282)
Complete follow up of all trials?	Yes	109 trials were identified of which 66 were included in the analysis. Reasons for exclusion were: closed as failed to accrue (n = 8); still open to accrual (n = 25); still open to follow up (n = 10) (page 282)
Publication ascertained through personal contact with investigators or sponsor?	Yes	"Supplemental information about recently analysed trials and clarifications on unclear or missing data were obtained from investigators and medical officers and staff responsible for the protocols." (page 282)
Definition of positive and negative findings clearly defined?	Yes	"In this article, a trial is called "positive" if a statistically significant finding (denoted by P < 0.05) had been found in the analysis of the data for a main efficacy end point defined in the protocol in favour of an experimental therapy arm. Trials with non statistically significant findings or favouring the control arm are called "negative ..." (page 282)
Possible confounders controlled for in the analysis	Yes	" .. the significance levels of the findings and other trial characteristics were used as covariates for the risk of publication in Cox proportional hazard regression. Trial characteristics included the actual sample size, the ratio of accrual compared with the originally anticipated (target) enrolment (typically based on power calculation), the trialist group, the age of the population (adult or paediatric), the trial domain (antiretroviral therapy vs complication of HIV), the presence or not of double blinding, and the place were data were managed (pharmaceutical industries or other)." (page 282)