The authors reported that fifteen RCTs were included (n=2,035 patients). The Jadad scores ranged from 2 to 5 (nine trials scored 5). However, there appeared to be thirteen unique references to trials in the tables.
There was evidence of statistical heterogeneity (p=0.0001, χ2=41.73) and the authors also reported clinical heterogeneity was present. The funnel plot and the Begg and Egger test did not indicate publication bias was present.
The relative risks and confidence intervals (CIs) of the 15 RCTs were reported individually due to heterogeneity. Twelve RCTs reported a statistically significant increase in analgesia with an anticonvulsant in diabetic neuropathy including: one trial of phenytoin, two trials of gabapentin, one trial of lamotrigine, one trial of valproic acid, five trials of pregabalin, one trial of topiramate and one trial of oxcarbazepine.
Subgroup analysis was performed on six RCTs (n=1,129 patients) that reported 50% or greater improvement in pain as the criteria for clinical effectiveness of the drug, had similar methodology and had a minimum five weeks follow-up. These investigated pregabalin, topiramate and oxcarbazepine. There was a statistically significant improvement in analgesia with an anticonvulsant (relative risk 2.33, 95% CI: 1.88 to 2.89). Pregabalin had the lowest necessary-number-to-treat of 3.24 (95% CI: 2.12 to 6.81). There was no evidence of statistical heterogeneity or publication bias in this subgroup.