Study | Adequate sequence generation | Concealment of allocation | Complete outcome reporting | Complete outcome data | Trial ended early (reason) | Overall risk of bias* |
---|---|---|---|---|---|---|
Guérin et al.,17 2013 | Yes | Centralized, Web-based | Yes | Yes | No | Low |
Taccone et al.,14 2009 | Yes | Central | Yes | No (mortality unknown for 1/175 in supine group, 1/169 in prone group) | No | Low |
Fernandez et al.,34 2008 | Yes | Central | Yes | No (mortality unknown for 1/20 in supine group, 1/22 in prone group) | Yes (slow enrolment) | Low |
Chan et al.,35 2007 | Yes | No (randomization table visible to person enrolling patients) | Yes | Yes | Yes (slow enrolment) | High† |
Mancebo et al.,36 2006 | Yes | Sealed opaque envelopes | Yes | No (mortality unknown for 2/62 in supine group, 4/80 in prone group) | Yes (slow enrolment) | Unclear‡ |
Curley et al.,37 2005 | Yes | Sealed opaque envelopes | Yes | Yes | Yes (futility stopping rule) | Low |
Voggenreiter et al.,38 2005 | Yes | Central | Yes | Yes | Yes (slow enrolment) | Low |
Guérin et al.,16 2004 | Yes | Sealed opaque envelopes | Yes | No (mortality unknown for 7/385 in supine group, 4/417 in prone group) | No | Unclear‡ |
Beuret et al.,39 2002 | Yes | Sealed opaque envelopes | Yes | No (mortality unknown for 2/28 in supine group, 0/25 in prone group) | Yes (slow enrolment) | Unclear‡ |
Watanabe et al.,40 2002 | No (alternate allocation) | No (alternate allocation) | No mortality data | NA | NR | High† |
Gattinoni et al.,15 2001 | Yes | Central | Yes | Yes | Yes (slow enrolment) | Low |
Note: NA = not applicable, NR = not reported.
↵* The Cochrane risk-of-bias tool22 was used to assess the risk of bias for each study. Low risk = bias, if present, is unlikely to alter the results seriously, unclear risk = bias raises some doubt about the results, high risk = bias may alter the results seriously.
↵† High risk of bias because of unconcealed allocation35 or alternate allocation.40
↵‡ Unclear risk of bias because of multiple possible sources of plausible bias: protective lung ventilation not mandated in both study arms,16,36,39 incomplete mortality data,16,36,39 early study termination36,39 and excessive crossover from prone to supine group (> 40%).16