What can we learn from Chinese randomized controlled trials? A systematic review and meta-analysis of Chinese venlafaxine studies.

This systematic review evaluated Chinese trials examining the efficacy of venlafaxine in the treatment of depression. Chinese databases CNKI and VIP and western databases were searched for blinded randomized controlled trial publications comparing venlafaxine to other antidepressants or placebo (in English or Chinese). Trials had to establish diagnosis of depression according to the Chinese Classification of Mental Disorders, Diagnostic and Statistical Manual of Mental Disorders, or International Classification of Diseases. Studies were excluded if more than 20% of participants had a primary diagnosis of dysthymia or if more than 15% had a primary diagnosis of bipolar disorder. Effect sizes were calculated as Hedges' g for rating scale scores and Mantel-Haenszel risk ratios (MH RR) for response and remission data. Effect sizes were combined in a fixed-effects model. A total of 25 studies were included. Nine trials compared venlafaxine to selective serotonin reuptake inhibitor; placebo-controlled trials were lacking. Quality was at best modest, and all trials were underpowered. There were more responders (MH RR, 1.08; 95% confidence interval [CI], 1.02-1.15) and remitters (MH RR, 1.12; 95% CI, 1.02-1.24) in venlafaxine groups compared with those in tricyclic antidepressant group. Hamilton Depression Rating Scale end point scores in the venlafaxine groups were lower (Hedges' g = 0.16; 95% CI, 0.04-0.27), and venlafaxine was better tolerated than tricyclic antidepressant (Hedges' g = 0.56; 95% CI, 0.37-0.74). There were no significant differences between venlafaxine and selective serotonin reuptake inhibitor on any of these parameters. Analyses of publication bias were inconclusive. Chinese researchers have published a number of randomized controlled trials comparing venlafaxine to active comparators, but study quality was found to be low. To make optimal use of their research potential Chinese, researchers will have to improve trial reporting and the peer-review process.