Q J Med 2003; 96: 379-380
© 2003 Association of Physicians
Correspondence |
The head-up tilt test for diagnosing chronic fatigue syndrome
Mayo Clinic, Rochester, Minnesota, USA e-mail: ghosh.amit{at}mayo.edu
Sir,
The recent paper by Naschitz et al.1 on the use of the head-up tilt test with haemodynamic instability score (HIS) in the diagnosis of chronic fatigue syndrome (CFS) provides additional insight about the role of dysautonomia in the pathogenesis of CFS. We would like to raise some points regarding the patient group studied.
The enrolment of clinically-diagnosed CFS patients and the awareness of diagnosis by technicians prior to performing the tilt test, could result in selection bias. Additionally, generalizing the result of the study, whose population was rich in patients with CFS (40/349, or 11%) to the general population (prevalence of CFS 0.07–0.2%) could be misleading. Using their results of a sensitivity of 90.3% and specificity of 84.5% for a cutoff of HIS >-0.98, a positive head-up tilt test in a patient presenting with fatigue in the general population would have a positive predictive value of only 0.37–1.15. This result, taken with the fact that around one-fifth of the patients developed a presyncopal or syncopal episode, would make the test less appealing to patients. However, in a patient presenting with fatigue where clinical diagnosis remained unclear despite lengthy evaluation, the head-up tilt test could be useful for narrowing down the range of diagnoses.
References
1. Naschitz JE, Rosner I, Rozenbaum M, et al. The head-up tilt test with haemodynamic instability score in diagnosing chronic fatigue syndrome. Q J Med 2003; 96:133–42.
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