Fig 11. Contour-Enhanced Funnel Plot of Acupuncture versus Sham-acupuncture for CLBP in Pain at immediate term.

Visual inspection of the funnel plot suggested some degree of asymmetry. Specifically, there was a relative lack of trials with negative results (i.e., fewer trials in areas of statistical nonsignificance), indicating a potential for publication bias; meanwhile, the dot on the lower left part of the Figure suggested an evidence of small-study effect.