Reply to Hurley

Excerpt

We thank A/Prof. Hurley for drawing further attention to the need for any meta-analysis to examine its candidate constituent trials for factors that might introduce bias. In the quoted example, the composite trials were potentially flawed in that antibiotic prophylaxis for ventilator-associated pneumonia might have increased the rate of pneumonia in control groups rather than decreasing the rate in intervention groups. We agree that identifying this situation is impossible if the data from the constituent trials are simply subjected to mathematical aggregation in a meta-analysis, whether the analysis is of aggregate or individual patient data (IPD). We therefore further agree that any meta-analysis must investigate the validity of its constituent studies. However, we disagree that coming to a misleading conclusion is more likely when individual patient data are properly used. Individual patient data increase the power of a meta-analysis to detect both overall and subgroup effects. As when using any more powerful tool, more care must be exercised to achieve the greater desired effects without undue danger. …