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Apparently conflicting meta-analyses on prophylactic negative pressure wound therapy after cesarean delivery

Published:April 26, 2018DOI:https://doi.org/10.1016/j.ajog.2018.04.034
      To the Editors:
      We read with interest 2 apparently discordant meta-analyses on the prophylactic negative-pressure wound therapy after cesarean delivery recently published in the American Journal of Obstetrics and Gynecology (AJOG)
      • Yu L.
      • Kronen R.J.
      • Simon L.E.
      • Stoll C.R.
      • Colditz G.A.
      • Tuuli M.G.
      Prophylactic negative-pressure wound therapy after cesarean is associated with reduced risk of surgical site infection: a systematic review and meta-analysis.
      and in Obstetrics and Gynecology.
      • Smid M.C.
      • Dotters-Katz S.K.
      • Grace M.
      • et al.
      Prophylactic negative pressure wound therapy for obese women after cesarean delivery: a systematic review and meta-analysis.
      According to the latter, “currently available evidence does not support negative-pressure wound therapy use among obese women for cesarean wound complication prevention” and the former considered the results suggestive of “a reduction in surgical site infection and overall wound complications.”
      Several sources of discordance between systematic reviews/meta-analyses have been described, including differences in objectives and methods or errors in implementation.
      • Jadad A.R.
      • Cook D.J.
      • Browman G.P.
      A guide to interpreting discordant systematic reviews.
      Regarding these 2 articles, their objectives were essentially the same, but there were differences in the search strategies, in study designs, and in outcomes selected for analysis. In the AJOG, both randomized controlled trials (RCTs) and cohort studies were used to compute pooled relative risk (RR) estimates with 95% confidence intervals (95% CI), whereas in Obstetrics and Gynecology only data from RCTs were analyzed. In the AJOG, the conclusions were driven by results regarding surgical site infection (RCTs: RR, 0.55; 95% CI, 0.35–0.87; cohort: RR, 0.32; 95% CI, 0.18–0.57; all studies: RR, 0.45; 95% CI, 0.31–0.66), despite data regarding other outcomes were also presented, including composite wound complications (RCTs: RR, 0.82; 95% CI, 0.57–1.18; cohort: RR, 0.45; 95% CI, 0.26–0.78; all studies: RR, 0.68; 95% CI, 0.49–0.94); in Obstetrics and Gynecology, the authors focused mostly on the composite outcome of wound complications (RCTs: RR, 0.97; 95% CI, 0.63–1.49). A composite outcome of wound infections was analyzed as well (RCTs: RR, 0.79; 95% CI, 0.44–1.41).
      Despite the fact that the search strategies were comprehensive and covered analogous periods in both reviews, there was no complete overlap between them. There was 1 additional RCT in the AJOG article;
      • Hyldig N.
      Incisional negative pressure wound therapy: the clinical effect on post-caesarean wound complications in obese women.
      had it been included in the Obstetrics and Gynecology meta-analysis, the conclusions would be essentially the same for composite wound complications (RR, 0.82; 95% CI, 0.57–1.18), and a negative significant association would have been obtained for surgical site infection. Also, 2 additional cohort studies were identified in the Obstetrics and Gynecology report but were not eligible for this meta-analysis.
      Summing up, weaker associations were obtained from RCTs and for the composite outcome of wound complications; the differences in the conclusions of these reviews were determined mostly by the choice of distinct primary outcomes by their authors. This is an example of how the conclusions of transparent systematic reviews/meta-analyses may be subjective and influenced by methodologic options made by the authors.

      References

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        • Kronen R.J.
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        Prophylactic negative-pressure wound therapy after cesarean is associated with reduced risk of surgical site infection: a systematic review and meta-analysis.
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        Prophylactic negative pressure wound therapy for obese women after cesarean delivery: a systematic review and meta-analysis.
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        A guide to interpreting discordant systematic reviews.
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        Incisional negative pressure wound therapy: the clinical effect on post-caesarean wound complications in obese women.
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