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. 2014 May 11:14:64.
doi: 10.1186/1471-2288-14-64.

Comparison of intervention effects in split-mouth and parallel-arm randomized controlled trials: a meta-epidemiological study

Violaine Smaïl-Faugeron  1 , Hélène Fron-Chabouis, Frédéric Courson, Pierre Durieux
Affiliations

Comparison of intervention effects in split-mouth and parallel-arm randomized controlled trials: a meta-epidemiological study

Violaine Smaïl-Faugeron et al. BMC Med Res Methodol. .

Erratum in

Abstract

Background: Split-mouth randomized controlled trials (RCTs) are popular in oral health research. Meta-analyses frequently include trials of both split-mouth and parallel-arm designs to derive combined intervention effects. However, carry-over effects may induce bias in split- mouth RCTs. We aimed to assess whether intervention effect estimates differ between split- mouth and parallel-arm RCTs investigating the same questions.

Methods: We performed a meta-epidemiological study. We systematically reviewed meta- analyses including both split-mouth and parallel-arm RCTs with binary or continuous outcomes published up to February 2013. Two independent authors selected studies and extracted data. We used a two-step approach to quantify the differences between split-mouth and parallel-arm RCTs: for each meta-analysis. First, we derived ratios of odds ratios (ROR) for dichotomous data and differences in standardized mean differences (∆SMD) for continuous data; second, we pooled RORs or ∆SMDs across meta-analyses by random-effects meta-analysis models.

Results: We selected 18 systematic reviews, for 15 meta-analyses with binary outcomes (28 split-mouth and 28 parallel-arm RCTs) and 19 meta-analyses with continuous outcomes (45 split-mouth and 48 parallel-arm RCTs). [corrected]. Effect estimates did not differ between split-mouth and parallel-arm RCTs (mean ROR, 0.96, 95% confidence interval 0.52-1.80; mean ∆SMD, 0.08, -0.14-0.30).

Conclusions: Our study did not provide sufficient evidence for a difference in intervention effect estimates derived from split-mouth and parallel-arm RCTs. Authors should consider including split-mouth RCTs in their meta-analyses with suitable and appropriate analysis.

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Figures

Figure 1
Figure 1
Flow diagram.
Figure 2
Figure 2
Difference in intervention effect estimates between split-mouth and parallel-arm randomized controlled trials for binary outcome data.
Figure 3
Figure 3
Difference in intervention effect estimates between split-mouth and parallel-arm randomized controlled trials for continuous outcome data.
See this image and copyright information in PMC

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