Results from a blind and a non-blind randomised trial run in parallel: experience from the Estonian Postmenopausal Hormone Therapy (EPHT) Trial

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dc.contributor.author Veerus, Piret -
dc.contributor.author Fischer, Krista -
dc.contributor.author Hakama, Matti -
dc.contributor.author Hemminki, Elina -
dc.contributor.author The, EPHT Trial -
dc.date.accessioned 2012-06-17T20:15:39Z
dc.date.available 2012-06-16 08:47:32 -
dc.date.available 2012-06-17T20:15:39Z
dc.date.issued 2012 -
dc.identifier.issn 1471-2288 -
dc.identifier.uri http://tampub.uta.fi/handle/10024/66110
dc.description BioMed Central Open access -
dc.description.abstract Background The Estonian Postmenopausal Hormone Therapy (EPHT) Trial assigned 4170 potential participants prior to recruitment to blind or non-blind hormone therapy (HT), with placebo or non-treatment the respective alternatives. Before having to decide on participation, women were told whether they had been randomised to the blind or non-blind trial. Eligible women who were still willing to join the trial were recruited. After recruitment participants in the non-blind trial (N = 1001) received open-label HT or no treatment, participants in the blind trial (N = 777) remained blinded until the end of the trial. The aim of this paper is to analyse the effect of blinding on internal and external validity of trial outcomes. Methods Effect of blinding was calculated as the hazard ratio of selected chronic diseases, total mortality and all outcomes. For analysing the effect of blinding on external validity, the hazard ratios from women recruited to the placebo arm and to the non-treatment arm were compared with those not recruited; for analysing the effect of blinding on internal validity, the hazard ratios from the blind trial were compared with those from the non-blind trial. Results The women recruited to the placebo arm had less cerebrovascular disease events (HR 0.43; 95% CI: 0.26-0.71) and all outcomes combined (HR 0.76; 95% CI: 0.63-0.91) than those who were not recruited. Among women recruited or not recruited to the non-treatment arm, no differences were observed for any of the outcomes studied. Among women recruited to the trial, the risk for coronary heart disease events (HR 0.77; 95% CI: 0.64-0.93), cerebrovascular disease events (HR 0.66; 95%CI: 0.47-0.92), and all outcomes combined (HR 0.82; 95% CI: 0.72-0.94) was smaller among participants in the blind trial than in the non-blind trial. There was no difference between the blind and the non-blind trial for total cancer (HR 0.95; 95% CI: 0.64-1.42), bone fractures (0.93; 95% CI: 0.74-1.16), and total mortality (HR 1.03; 95% CI: 0.53-1.98). Conclusions The results from blind and non-blind trials may differ, even if the target population is the same. Blinding may influence both internal and external validity. The effect of blinding may vary for different outcome events. -
dc.language.iso en -
dc.title Results from a blind and a non-blind randomised trial run in parallel: experience from the Estonian Postmenopausal Hormone Therapy (EPHT) Trial -
dc.type fi=Artikkeli aikakauslehdessä | en=Journal article| -
dc.identifier.urn urn:nbn:uta-3-981 -
dc.identifier.doi 10.1186/1471-2288-12-44 -
dc.type.version fi=Kustantajan versio | en=Publisher's version| -
dc.subject.okm fi=Terveystiede | en=Health care science| -
dc.administrativeunit fi=Terveystieteiden yksikkö | en=School of Health Sciences| -
dc.journal.title BMC Medical Research Methodology -
dc.journal.volume 12 -
dc.journal.number 44 -
dc.journal.volumepagerange 1-11 -
dc.oldstats 19 -

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