Effect of conventional combined orthodontic-surgical treatment on oral health-related quality of life: A systematic review and meta-analysis. Yi J, Lu W, Xiao J, Li X, Li Y, Zhao Z. Am J Orthod Dentofacial Orthop 2019; 156:29-43.
Government National Natural Science Foundation of China (grant 81801018) and Orthodontic National Key Clinical Specialty Program of China, West China Hospital of Stomatology, Sichuan University.
Systematic review with meta-analysis.

Combined Orthodontic-Surgical Treatment May Be an Effective Choice to Improve Oral Health-Related Quality of Life for Individuals Affected With Severe Dentofacial Deformities.

Analysis of rare binary events is an important problem for biomedical researchers. Due to the sparsity of events in such problems, meta-analysis that integrates information across multiple studies can be applied to increase the efficiency of statistical inference. Although it is critical to examine whether the effect sizes are homogeneous across all studies, a comprehensive review of homogeneity tests has been lacking, and in particular, no attention has been paid to infrequent dichotomous outcomes. We systematically review statistical methods for homogeneity testing. By conducting an extensive simulation analysis and two case studies, we examine the performance of 30 tests in meta-analysis of rare binary outcomes. When using log-odds ratio as the association measure, our simulation results suggest that there is no uniform winner. However, we recommend the test proposed by Kulinskaya and Dollinger (BMC Med Res Methodol, 2015, 15), which uses a gamma distribution to approximate the null distribution, for its generally good performance; for very rare events coupled with small within-study sample sizes, in addition to the Kulinskaya-Dollinger test, we further recommend the conditional score test based on the random-effects hypergeometric model proposed by Liang and Self (Biometrika, 1985, 72:353-358). One should be cautious about the use of the Wald tests, the Lipsitz tests (Biometrics, 1998, 54:148-160), and tests proposed by Bhaumik et al (J Am Stat Assoc, 2012, 107:555-567).

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