Figure 1: Published positivity rates of tilt testing in different populations. The upper band in black shows studies, which estimate the sensitivity of the test when the history strongly suggested vasovagal syncope. The middle band in red show studies of patients considered likely to have arrhythmia or structural heart disease as cause of syncope or unexplained syncope. The lower band in green reports studies using tilt testing in populations with no history of syncope yielding estimates of specificity. The drug challenge used or none (passive) is quoted in brackets and the references are given in subsequent brackets. Clom = Clomipramine, GTN = Glyceryl trinitrate.