The head-up tilt test with haemodynamic instability score in diagnosing chronic fatigue syndrome

Summary Background: Studying patients with chronic fatigue syndrome (CFS), we have developed a method that uses a head-up tilt test (HUTT) to estimate BP and HR instability during tilt, expressed as a ‘haemodynamic instability score’ (HIS). Aim: To assess HIS sensitivity and specificity in the diagnosis of CFS. Design: Prospective controlled study. Methods: Patients with CFS (n= 40), non-CFS chronic fatigue (n=73), fibromyalgia (n =41), neurally mediated syncope (n= 58), generalized anxiety disorder (n =28), familial Mediterranean fever (n= 50), arterial hypertension (n=28), and healthy subjects (n =59) were evaluated with a standardized head-up tilt test (HUTT). The HIS was calculated from blood pressure (BP) and heart rate (HR) changes during the HUTT. Results: The tilt was prematurely terminated in 22% of CFS patients when postural symptoms occurred and the HIS could not be calculated. In the remainder, the median(IQR) HIS values were: CFS q2.14(4.67), non-CFS fatigue � 3.98(5.35), fibromyalgia � 2.81(2.62), syncope � 3.7(4.36), generalized anxiety disorder � 0.21(6.05), healthy controls � 2.66(3.14), FMF � 5.09(6.41), hypertensives � 5.35(2.74) (p-0.0001 vs. CFS in all groups, except for anxiety disorder, p=NS). The sensitivity for CFS at HIS )� 0.98 cut-off was 90.3% and the overall specificity was 84.5%. Discussion: There is a particular dysautonomia in CFS that differs from dysautonomia in other disorders, characterized by HIS )� 0.98. The HIS can reinforce the clinician’s diagnosis by providing objective criteria for the assessment of CFS, which until now, could only be subjectively inferred.