Fig. 4

Funnel plot of published studies evaluating the unstimulated whole salivary flow rate in patients with Sjögren’s Syndrome compared to controls (healthy subjects and patients with non-SS sicca). It shows an important publication bias with an asymmetric article distribution. A funnel plot of standard error versus the unstimulated whole salivary flow difference in means is shown. Visual inspection of the funnel plot (scatter diagram) shows asymmetric article distribution confirmed by an Egger’s regression test (P=0.0001). MD: mean difference; SE: Standard error