Text Box: HEAD-UP TILT TEST WITHOUT INTRAVASCULAR CANNULATION IN CHILDREN AND ADOLESCENTS Sung RYT1, Yu CW1, Ng Eddie2, Du ZD1, Tomlinson Brian3, Tam Michael SC 2 Departments of 1Paediatrics, 3Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong; 2Department of Physiology, Chinese University of Hong Kong Background: Previous studies of head-up tilt test have shown that testing at high degrees lacks specificity in children. We suspected that the high false positive rate might be related to the intravascular catheter and other maneuvers incorporated in the test and therefore studied the sensitivity and specificity of standing and HUT at 80° without any invasive procedure and other maneuvers in children and adolescents. Methods: 23 patients (11.8 + 2.7 years) with recurrent typical neurally mediated syncope and 35 normal control children (11.6 + 3.0 years) underwent motionless standing for 15 minutes and tilting to 80° for 30 minutes. Continuous finger arterial pressure monitoring and ECG were performed during the test. Results: Eight (35%) of the 23 patients developed symptoms of near syncope during motionless standing. 13(57%) of them had positive results at 80° tilting for 30 minutes. The symptoms of syncope were not always corresponding to excessive haemodynamic changes. None of the controls developed any symptoms or excessive hemodynamic changes. Conclusion: Without intravascular instrumentation and other autonomic maneuvers, active motionless standing or HUT at 80° for 30 minutes is highly specific but of limited sensitivity for the investigation of vasovagal syncope. 2374