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Single fetal demise following fetoscopic ablation for twin-to-twin transfusion syndrome—cohort study, systematic review and meta-analysis: a comment

Published:April 12, 2022DOI:https://doi.org/10.1016/j.ajog.2022.04.006
      To the Editors:
      We read with interest the cohort study, systematic review, and meta-analysis conducted by Mustafa et al.
      • Mustafa H.J.
      • Javinani A.
      • Goetzinger K.
      • et al.
      Single fetal demise following fetoscopic ablation for twin-to-twin transfusion syndrome-cohort study, systematic review, and meta-analysis.
      The study addressed pregnancies with twin-to-twin transfusion syndrome that underwent fetoscopic laser photocoagulation (FLP) to identify risk factors for donor and recipient demise. For operative factors, the study used the standardized mean differences (SMDs) to investigate the influence of gestational age (GA) at FLP, procedure duration, and number of anastomoses on donor demise and fetal demise. Based on the findings, the study concluded that earlier GA at FLP had no to a very small negative effect in increasing donor and recipient demise (donor demise: SMD, −0.14 [95% confidence interval (CI), −0.26 to −0.03]; recipient demise: SMD, −0.18 [95% CI, −0.32 to −0.04]), longer procedure duration had a small positive effect in decreasing donor demise (SMD, 0.30; 95% CI, 0.04–0.57), and total number of anastomoses had no effect on fetal demise (SMD, −0.04; 95% CI, −0.18 to 0.10). However, when considering the limitation of SMD, this conclusion might be inappropriate.
      It could be misleading to conclude by relying on SMD results (particularly when the SMD effect is small) in a meta-analysis, because the SMD method has difficulties, including (1) ignoring a critical question (whether the effect is clinically important) and (2) vulnerability to varying degrees of heterogeneity in the underlying populations and difficulties in interpretation.
      • Thorlund K.
      • Walter S.D.
      • Johnston B.C.
      • Furukawa T.A.
      • Guyatt G.H.
      Pooling health-related quality of life outcomes in meta-analysis-a tutorial and review of methods for enhancing interpretability.
      ,
      • Murad M.H.
      • Wang Z.
      • Chu H.
      • Lin L.
      When continuous outcomes are measured using different scales: guide for meta-analysis and interpretation.
      To minimize the bias, we suggest that the authors consider referring to the minimally important difference (MID; defined as the smallest amount of improvement in a treatment outcome that patients recognize as important
      • Schünemann H.J.
      • Guyatt G.H.
      Commentary--goodbye M(C)ID! Hello MID, where do you come from?.
      ), which would help readers further understand whether the small effect is clinically important. The authors could identify the specific MID from the publications; if not available, they could also define the MID based on clinical experts’ consensus. We believe this would help readers further understand the findings and would also provide valuable information to achieve more reliable conclusions.

      References

        • Mustafa H.J.
        • Javinani A.
        • Goetzinger K.
        • et al.
        Single fetal demise following fetoscopic ablation for twin-to-twin transfusion syndrome-cohort study, systematic review, and meta-analysis.
        Am J Obstet Gynecol. 2022; ([Epub ahead of print])
        • Thorlund K.
        • Walter S.D.
        • Johnston B.C.
        • Furukawa T.A.
        • Guyatt G.H.
        Pooling health-related quality of life outcomes in meta-analysis-a tutorial and review of methods for enhancing interpretability.
        Res Synth Methods. 2011; 2: 188-203
        • Murad M.H.
        • Wang Z.
        • Chu H.
        • Lin L.
        When continuous outcomes are measured using different scales: guide for meta-analysis and interpretation.
        BMJ. 2019; 364: k4817
        • Schünemann H.J.
        • Guyatt G.H.
        Commentary--goodbye M(C)ID! Hello MID, where do you come from?.
        Health Serv Res. 2005; 40: 593-597

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