Diagnostic accuracy of symptoms characterising chronic fatigue syndrome (PFL, 2010)

WillowJ

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Davenport TE, Stevens SR, Baroni K, Van Ness M, Snell CR. "Diagnostic accuracy of symptoms characterising chronic fatigue syndrome." Disabil Rehabil. 2011 Jan 6. [Epub ahead of print] PMID: 21208154

Department of Physical Therapy, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA, USA.

Abstract
Purpose. To determine the diagnostic accuracy for single symptoms and clusters of symptoms to distinguish between individuals with and without chronic fatigue syndrome (CFS). Methods. A cohort study was conducted in an exercise physiology laboratory in an academic setting. Thirty subjects participated in this study (n = 16 individuals with CFS; n = 14 non-disabled sedentary matched control subjects). An open-ended symptom questionnaire was administered 1 week following the second of two maximal cardiopulmonary exercise tests administered 24 h apart.

Results. Receiver operating characteristics (ROC) curve analysis was significant for failure to recover within 1 day (area under the curve = 0.864, 95% confidence interval [CI]: 0.706-1.00, p = 0.001) but not within 7 days. Clinimetric properties of failure to recover within 1 day to predict membership in the CFS cohort were sensitivity 0.80, specificity 0.93, positive predictive value 0.92, negative predictive value 0.81, positive likelihood ratio 11.4, and negative likelihood ratio 0.22.

Fatigue demonstrated high sensitivity and modest specificity to distinguish between cohorts, while neuroendocrine dysfunction, immune dysfunction, pain, and sleep disturbance demonstrated high specificity and modest sensitivity. ROC analysis suggested cut-point of two associated symptoms (0.871, 95% CI: 0.717-1.00, p < 0.001). A significant binary logistic regression model (p < 0.001) revealed immune abnormalities, sleep disturbance and pain accurately classified 92% of individuals with CFS and 88% of control subjects.

Conclusions. A cluster of associated symptoms distinguishes between individuals with and without CFS. Fewer associated symptoms may be necessary to establish a diagnosis of CFS than currently described.
 

Dolphin

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I had wondered could this be some of the same data set as:

Postexertional malaise in women with chronic fatigue syndrome.
VanNess JM, Stevens SR, Bateman L, Stiles TL, Snell CR.
J Womens Health (Larchmt). 2010 Feb;19(2):239-44.
but no, it was confirmed to me that they are different patients which is good.
 
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Davenport TE, Stevens SR, Baroni K, Van Ness M, Snell CR. "Diagnostic accuracy of symptoms characterising chronic fatigue syndrome." Disabil Rehabil. 2011 Jan 6. [Epub ahead of print] PMID: 21208154

Department of Physical Therapy, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA, USA.
Anyone got a copy of this? I'd love to read it.
thanks
 
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Oh. Is that it?

My main response on reading this study was a long sigh.

This paper from Pacific Labs has been expected for some time and I'd hoped it would give us at least a few drops from the Holy Grail: objective measures of redcued CFS patient capability. Eg reduced Anaerobic Threshold VO2 after a second round of maximal exercise, as discussed by Lannie on her excellent blog about Pacific testing.

Instead the study gave some not-that-impressive diagnostic tests based on subjective response to maximal exercise. I'm pretty sure that Lenny Jason achieved diagnostic results as good as this using a simple questionnaire about post-exertional fatigue.

I wonder if this study originally aimed to provide the sort of objective measures discussed by Lannie, since it used TWO maximal exercise tests within 24 hours, a key part of testing for objective changes. To just measure PEM after a maximal exercise test you only really need the one test - which is exactly the approach used by this same group last year: Postexertional malaise in women with chronic fatigue syndrome.

That aside, the small convenience sample used for this study looks rather suspect. 25% (4/16) reported making a full recovery within 24 hours of the the two maximal tests. This strikes me as extraordinary and I suspect it is not at all representative of the CFS patient population as the whole. These surprisingly good recovery rates also probably explain the relatively low specificity of the tests: if none of the CFS patients had fully recovered within 24 hours (as was the case in the 2010 paper mentioned above) then the tests would have given very high specificity - and sensitivity too.

Finally, given how many CFS patients report problems with Graded Exercise therapy, which is rarely maximal, requiring 2 maximal exertion tests within 24 hours for diagnosis is probably neither feasible nor ethical, at least not for all patients,

I should say that I am very interested in what Pacific Labs are trying to do here, not so much as a diagnositic test but in terms of trying to understand what is really going in on CFS. But unfortunately this particular paper doesn't seem to take us any further forward.