Figure Summary receiver operator characteristic curve (SROC) for the most sensitive assay type reported from each of the 22 studies with complete values for true positive, false positive, true negative, false negative. This included papers with a range of different positivity thresholds for stimulation index (SI) (SI range between 2 to 3). Individual study values plotted and colour coded to reflect the assay type and size to represent number of participants. AUC 0.788, I2 55.3% (27.9% - 72.4%), tau2 = 0.252, p-value <0.0001