Assessment issues from biological to behavioral

Session 6

Structural Equation Modeling (SEM) is a data-analytic technique. Brian Gurbaxani (Zurich, Switzerland) has used it to look at CFS heterogeneity. This is an attempt to integrate the variables in CFS particularly in relation to HPA and stress-related variables.

Leighton Barnden (Adelaide, Australia) analyzed brain MRI images in 25 CFS subjects and 25 matching controls. Voxel-based analysis of the images was used, and a voxel was described as a 3D pixel. There were changes in the midbrain of patients, which could account for some of the CFS symptoms, such as changes in the reticular activating system and the red nucleus. No changes were seen in the amygdala and there was no significant difference in grey or white matter. Changes in the medulla and insular were consistent with the autonomic dysfunction seen in CFS.

A diagnostic test for the identification of metabolic dysfunction was discussed by J.Mark VanNess (Stockton, USA). Two graded exercise tests with cardio-pulmonary analysis were performed within 24 hours of each other. There was a "fatigue effect" of prior physical activity not characteristic of other illnesses. There was reduction of peak oxygen consumption and/or oxygen consumption at anaerobic threshold in CFS patients and in particular those with a high viral load. This provides evidence of metabolic dysfunction.

Norman Booth (Oxford, UK) described work on mitochondrial dysfunction in CFS. An "ATP profile test" has been designed for CFS and other energy depleted conditions. 5 factors were collated and multiplied together to produce the mitochondrial energy score. CFS affects every cell in the body and a mitochondrial disorder seems a likely possibility. This test is able to differentiate patients whose fatigue is due to psychological factors from those who have insufficient energy due to cellular respiration dysfunction.