Study search and study characteristics
A total of 8645 publications were retrieved; of these, 22 RCTs (n = 1079 participants) were included in the present network meta-analysis. A flow chart depicting the literature search process based on PICO is presented in Figure 1. Overall, two studies evaluated and compared Myo-inositol (MI) and Myo-inositol + D-chiro-inositol (MI + DCI) combination treatment (72 women), one study compared MI and DCI (50 women), and the remaining RCTs offered a comparison of Met (19 trials; 455 women) and the following interventions: thiazolidinediones (TZDs) (ten trials; 280 women), Met + TZDs (three trials; 89 women), MI (four trials; 110 women), MI + DCI (one trial; 32 women), berberine (BBR) (one trial; 26 women), and Met + BBR (two trials; 70 women). The evidence map for the aforementioned interventions is shown in Figure 2.
Table 1 shows the characteristics of the included studies. These RCTs were conducted in various countries, published in English or Chinese, and participants were recruited from an outpatient clinic or a hospital. Trials were generally similar with respect to patient baseline characteristics for most outcomes. In summary, a total of 1079 women with PCOS were randomized to receive eight different interventions (Met, TZDs, BBR, MI, DCI, MI + DCI, Met + TZDs, and Met + BBR).
The risk of bias assessment is shown in Figure 3. Of the 22 included trials, seven were at a high risk of bias due to lack of blinding, leading to performance and detection bias; and six studies were at a high risk of bias for incomplete outcome data, leading to attrition bias. All Egger regression asymmetry tests showed P > 0.05 (Supplementary Appendix 1).
Efficacy outcomes
Table 2A and Table 2B summarizes the NMA and TMA results for positive efficacy outcomes. Furthermore, other efficacy outcomes, details of the Forest plots, and SUCRA curves are presented in Supplementary Appendix 2.
Menstrual frequency
With respect to improving menstrual frequency, our TMA showed that Met + TZDs (OR 3.91 [95% CI 1.75-8.72]; P = 0.88, I² = 0%) was more efficacious than Met alone, while MI + DCI (OR 21.92 [95% CI 2.99-160.44]; P = 0.38, I² = 0%) was more efficacious than MI alone. The NMA revealed that MI + DCI was more efficacious than Met (OR 14.70 [95% CI 2.31-93.58]) and MI (OR 16.51 [95% CI 2.56-106.64]). MI + DCI was ranked best at improving menstrual frequency.
Hyperandrogenism
In terms of reducing TT, the TMA and NMA both revealed that Met + BBR [(TMA: MD -11.53 [95% CI (-16.91)-(-6.15)]; P = 1.00, I² = 0%; NMA: MD -11.53 [95% CI (-17.62)-(-5.44)]) and Met + TZDs [(TMA: MD -3.14 [95% CI (-6.19)-(-0.09)]; P = 0.44, I² = 0%; NMA: MD -3.66 [95% CI (-6.60)-(-0.72)] were superior to Met alone. The NMA revealed that MI + DCI was more efficacious than Met, MI, and DCI [MDs ranging from -6.72 [95% CI (-10.24) -(-3.20)] for Met to -7.70 [95% CI (-14.90)-(-0.50)] for DCI]). Treatment with TZDs was less efficacious than Met (MD 3.90 [95% CI 1.10-6.71]). The SUCRA values were as follows: Met + BBR (92.2%), MI + DCI (75.4%), and Met + TZDs (59.4%). No difference was found in comparisons of SHBG, AND, and mF-G scores.
Obesity
With respect to BMI reduction, the TMA showed that Met + BBR (MD -1.85 [95% CI (-2.76)-(-0.94)]; P = 0.32, I² = 0%) was superior to Met monotherapy, whereas the NMA revealed that Met + BBR was more efficacious than Met, MI, TZDs, and Met + TZDs (MDs ranging from -1.85 [95% CI (-2.76)-(-0.94)] for Met to -3.08 [95% CI (-4.10)-(-2.05)] for TZDs). Met + BBR ranked best among all the treatments at reducing BMI. However, both the TMA and NMA revealed that there was no significant difference between the groups with respect to WHR reduction.
Glycometabolism
With respect to lowering FPG, the TMA revealed that there were no significant differences between each of the investigated agents. The NMA revealed that TZDs (MD -0.21 [95% CI (-0.21)-(-0.02)]) were more efficacious than Met. Additionally, with respect to lowering FINS, the TMA revealed that Met + TZDs (MD -1.83 [95% CI (-3.12)-(-0.55)]; P = 0.19, I² = 37%) was more efficacious than Met alone. The NMA did not reveal any significant differences among the groups.
With respect to decrease in HOMA-IR, the TMA showed that TZDs (MD -0.92 [95% CI (-1.64)-(-0.19)]; P <0.00001, I² = 97%), Met + TZDs (MD -0.85 [95% CI (-1.21)-(-0.49)]; P = 0.04, I² = 65%), and Met + BBR (MD -0.25 [95% CI (-0.36)-(-0.14)]; P = 0.37, I² = 0%) were more efficacious than Met alone. The NMA revealed that TZDs, Met + TZDs, and MI + DCI were all superior to Met (MDs ranging from -0.72 [95% CI (-1.11)-(-0.34)] for TZDs to -0.89 [95% CI (-1.46)-(-0.32)] for MI + DCI), with MI + DCI being ranked the best with a SUCRA value of 80.8%. The SUCRA values for the other agents were as follows: 79.9% and 68.6% for Met + TZDs and TZDs, respectively.
Lipid levels
Parameters assessed for improvement in blood lipids included TG, TC, HDL-C, and LDL-C. In terms of reducing TG and TC levels, the TMA revealed that Met + TZDs (TG: MD -0.24 [95% CI (-0.43)-(-0.06)]; P = 0.74, I² = 0%; TC: MD -0.30 [95% CI (-0.53)-(-0.07)]; P = 0.98, I² = 0%) was more efficacious than Met alone. In terms of reducing levels of TG, the NMA showed that Met + TZDs was superior to Met (MD -0.08 [95% CI (-0.16)-(0.00)]) and TZDs (MD -0.51 [95% CI (-0.88)-(-0.14)]), and was the best intervention among treatments. The NMA also showed that BBR (MD -0.03 [95% CI (-0.06)-(0.00)]) was more efficacious than Met. However, for TC no significant differences were found in the NMA.
Furthermore, the TMA also suggested that MI (MD 0.05 [95% CI 0.03-0.07]; P = 0.10, I² = 57%) was associated with higher HDL-C than Met. The NMA revealed that treatment with TZDs was superior to Met in increasing HDL-C (MD 0.13 [95% CI 0.03-0.24]) and decreasing LDL-C (MD -0.19 [95% CI (-0.27)-(-0.11)]) and was the best intervention among the different treatments.
Adverse events
In terms of the frequency of gastrointestinal adverse events during treatment, both TMA and NMA revealed that treatment with TZDs (TMA: OR 0.11 [95% CI 0.03-0.41]; P = 0.88, I² = 0%; NMA: OR 0.13 [95% CI 0.04-0.46]) was inferior to Met. With respect to the incidence of peripheral edema, the TMA revealed that TZDs were more frequent than Met (OR 67.89 [95% CI 3.96, 1163.28]; P&I² NA), no significant differences were found in the NMA. Furthermore, both the TMA and NMA did not show any significant differences between the different treatment regimens for the incidence rate of muscle spasms, while no drug increased odds of transaminase abnormalities. Of note, these results should be interpreted with caution since results for MI, MI + DCI, and BBR were based on a single trial, and in some of the trials the description of adverse events was subjective and unclear.