Four trials (n=429 wounds; 209 with drainage) were eligible for inclusion. The number of participants ranged from 96 to 127. Three studies received a Jadad score of 2 and the other a score of 3.
There was no statistical difference between patients with a drain and those without in the risk of wound infection (three trials). The pooled odds ratio for this outcome in the meta-analysis plot was 1.04 (95% CI 0.56, 1.91; p = 0.94), although it was reported as 1.56 in the text.
There was no statistical difference between groups for the outcomes of haematoma formation (three trials, odds ratio of 2.01, 95% CI 0.42, 9.93; p = 0.38) or seroma and lymphocele formation (four trials, pooled odds ratio 0.62, 95% CI 0.37, 1.04; p = 0.07).
There was no evidence of statistical heterogeneity between studies for any of the outcomes, but the authors stated that apparent methodological heterogeneity between studies may have influenced the meta-analytic results. There was evidence of publication bias for seroma/lymphocele formation (p = 0.02), but not for wound infection. There were too few studies to assess publication bias for haematoma formation.