Entry criteria were too dissimilar for studies to be combined for meta-analysis

EDITOR—De Ferranti et al's meta-analysis on antibiotics in acute sinusitis could be criticised in many ways.1 Published in the General Practice section of the BMJ, it is presumably aimed at general practitioners.

The authors first looked at randomised controlled trials on the effectiveness of antibiotic against non-antibiotic management and then carried out a meta-analysis of the six placebo controlled trials they identified. It is implied that the patients being randomised were similar in each of the studies, so that a meta-analysis could be performed. This is not the case. One of the papers (that by Wald et al, in 1986) concerned the treatment of children and cannot be combined with the other five papers, which were adult studies.

Table 1 in the authors' paper shows the clinical settings and the entry criteria for the other five studies. In looking at this, readers have to identify which study is applicable to their own clinical setting. …