A randomised controlled trial of the outcome of health assessment of people aged 75 years and over. Bias in reporting clinical trials. Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses?
To measure the outcomes of a health assessment, conducted by a nurse, of people aged 75 years and older (75+HA) living independently in their own homes.
                Randomised controlled trial (RCT).
                A convenience sample of six general practices within the Adelaide Western Division of General Practice (AWDGP). A random sample of 100 participants was drawn from practice age-sex registers. Data were collected in initial visits between 1 August 1998 and February 1999, then in follow-up visits one year later.
                Participants were aged 75 years and over on 1 August 1998 and living independently in the community. 145 eligible patients were invited to join the study, and 100 of these consented to enrol (69%).
                A 75+HA conducted in the participant's home by a nurse and reported to their usual general practitioner.
                Primary: number of problems in each group; number of participants with problems; and mortality. Secondary: physical function; psychological (including cognitive) function; falls; and admission to institution.
                There were no significant differences between the control and intervention groups at follow-up in the number of problems, the number of participants with problems, or mortality. In the intervention group, there was significant improvement in self-rated health, geriatric depression score (GDS 15), and number of falls.
                This RCT has not demonstrated improvement in health status of the intervention group which received a 75+HA compared with a control group left to usual care. The primary aim of the present study was to identify possible occurrence of selective reporting of the results of clinical trials to the Finnish National Agency for Medicines. Selective reporting may lead to poorly informed action or inaction by regulatory authorities.
                In 1987, 274 clinical drug trials were notified to the Finnish National Agency for Medicines. By December 1993, final reports had been received from 68 of these trials and statements that the trial had been suspended from 24 trials. The sponsors of the non-reported trials were requested to report the outcome. The outcomes, if any, of all reported and non-reported trials were classified as positive, inconclusive or negative.
                The total number of trials with positive, inconclusive or negative outcome were 111, 33 and 44, respectively; the outcomes of 86 trials could not be assessed. Final reports were received from 42/111 (38%) trials with positive, 6/33 (18%) with inconclusive and 9/44 (20%) with negative outcomes.
                Substantial evidence of selective reporting was detected, since trials with positive outcome resulted more often in submission of final report to regulatory authority than those with inconclusive or negative outcomes. The inclusion of only a subset of all available evidence in a meta-analysis may introduce biases and threaten its validity; this is particularly likely if the subset of included studies differ from those not included, which may be the case for published and grey literature (unpublished studies, with limited distribution). We set out to examine whether exclusion of grey literature, compared with its inclusion in meta-analysis, provides different estimates of the effectiveness of interventions assessed in randomised trials.
                From a random sample of 135 meta-analyses, we identified and retrieved 33 publications that included both grey and published primary studies. The 33 publications contributed 41 separate meta-analyses from several disease areas. General characteristics of the meta-analyses and associated studies and outcome data at the trial level were collected. We explored the effects of the inclusion of grey literature on the quantitative results using logistic-regression analyses.
                33% of the meta-analyses were found to include some form of grey literature. The grey literature, when included, accounts for between 4.5% and 75% of the studies in a meta-analysis. On average, published work, compared with grey literature, yielded significantly larger estimates of the intervention effect by 15% (ratio of odds ratios=1.15 [95% CI 1.04-1.28]). Excluding abstracts from the analysis further compounded the exaggeration (1.33 [1.10-1.60]).
                The exclusion of grey literature from meta-analyses can lead to exaggerated estimates of intervention effectiveness. In general, meta-analysts should attempt to identify, retrieve, and include all reports, grey and published, that meet predefined inclusion criteria.
It is not possible to draw any conclusions from this review. The number of people included in the studies is less than 50 and the reported results are inadequate.