Fatigue Scales and Chronic Fatigue Syndrome: Issues of Sensitivity and Specificity

Dolphin

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The full text of this is available for free at:
http://www.dsq-sds.org/article/view/1375/1540

Disability Studies Quarterly, Vol 31, No 1 (2011)

Fatigue Scales And Chronic Fatigue Syndrome: Issues Of Sensitivity And Specificity

*Leonard Jason, Jason Meredyth Evans, Molly Brown, Nicole Porter, Abigail Brown, Jessica Hunnell, Valerie Anderson, Athena Lerch*

Keywords:
chronic fatigue syndrome, fatigue, fatigue scales, sensitivity and specificity

Abstract (one paragraph - I've given each line a paragraph)

Few studies have explored issues of sensitivity and specificity for using the fatigue construct to identify patients meeting chronic fatigue syndrome (CFS) criteria.

In this article, we examine the sensitivity and specificity of several fatigue scales that have attempted to define severe fatigue within CFS.

Using Receiver Operating Characteristic (ROC) curve analysis, we found most scales and sub-scales had either significant specificity and/or sensitivity problems. However, the post-exertional subscale of the ME/CFS Fatigue Types Questionnaire (Jason, Jessen, et al., 2009) was the most promising in terms of specificity and sensitivity.

Among the more traditional fatigue scales, Krupp, LaRocca, Muir-Nash, and Steinberg's (1989) Fatigue Severity Scale had the best ability to differentiate CFS from healthy controls.

Selecting questions, scales and cut off points to measure fatigue must be done with extreme care in order to successfully identify CFS cases.
 

Dolphin

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2nd part of this study shows the problems with empiric criteria (Reeves et al., 2005)

The 2nd part of this study shows the problems with empiric criteria (Reeves et al., 2005).

This part (part 2) is basically the same data that is in:
L. A. Jason, N. Najar, N. Porter and C. Reh, “Evaluating the Centers for Disease Control’s Empirical Chronic Fatigue Syndrome Case Definition,” Journal of Disability Policy Studies, Vol. 20, 2009, pp. 93-100.
but is now available in open access form.
 

Dolphin

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One way this paper can be put into practice

One way this paper can be put into practice
Endnotes

1.Five of these MFTQ Post-Exertion items with the highest factor loadings included: dead, heavy feeling after starting to exercise; next day soreness or fatigue after non-strenuous everyday activities; mentally tired after the slightest effort; physically drained or sick after mild activity; and minimum exercise makes you physically tired. Given the importance of this sub-scale, in addition to a total score, we decided to investigate how many items might be needed to differentiate CFS from controls. We scored an item as being a positive indicator of CFS if it had a frequency of "often" or more and a severity rating of 50 or higher on a 100 point severity scale. We created a variable that indicated whether a person had 0 to 5 Post-Exertional items, and then used this variable in a ROC analysis. The ROC resulted in an AUC of .94 (SE = .02, 95% CI, .90 to .97). The highest sensitivity and specificity occurred for one or more items (.91 and .90, respectively). We therefore recommend that if a person has one or more symptoms, they would meet criteria for Post-Exertional fatigue.
(I checked the original paper and there are actually 7 items in the full scale. The other two are: "Muscle weakness even after resting" and "Limbs feel heavy when not moving them": link: http://www.dsq-sds.org/article/view/938/1113
 

WillowJ

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Identification of CFS samples using methods with optimal sensitivity and specificity will allow for a comparison of findings across different studies, as well as enhance the capability of researchers to identify biological markers for this illness. Substantial implications arise for the CFS patient community if CFS research is improved through the consistent utilization of empirically-derived screening instruments. For example, patients with CFS often report dissatisfaction with treatments they receive, which is in part due to the poor understanding of the etiology of this disabling condition (Ax, Gregg, & Jones, 1997; Deale & Wessely, 2001). If research is conducted on more homogeneous samples and key biological markers are found across studies, then more appropriate treatment options can be developed for CFS. Furthermore, if greater credibility is given to CFS as a medical illness among medical professionals, patients may garner improved support from their health care providers (Ax et al., 1997).
Very good point. Thanks so much, Jason & team!

Ax, S., Gregg, V. H., & Jones, D. (1997). Chronic fatigue syndrome: Sufferers' evaluation of medical support. Journal of the Royal Society of Medicine, 90, 250-254.
 

CBS

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Dolphin,

Thanks for the post. I have to say, I'm not surprised by the findings. While I am a huge fan of Jason and his team, I think we're wasting our time focusing on fatigue.

I am going to say this until it sinks in - Most of us are tired but not fatigued. We do not meet the criteria for fatigue as it is traditionally defined in physiological research (Alan Light - CFSAC; Oct, 2010). Fatigue as it is used by the CDC in their name "CFS" is done so in the most general poorly defined popular sense (and in a manner that is consistent with depression). Those of us that meet the Canadian Consensus Dx criteria couldn't get into a CDC study (quite literally for the life of us) if we tried.

The best outcome of this study would be if it served to move the focus off of fatigue and on to the other increasingly well documented biomarkers.

WE MUST STOP USING THE WORD FATIGUE UNLESS WE"RE TALKING ABOUT A CDC DEFINITION OR A CDC STUDY!
 

Dolphin

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Dolphin,

Thanks for the post. I have to say, I'm not surprised by the findings. While I am a huge fan of Jason and his team, I think we're wasting our time focusing on fatigue.

I am going to say this until it sinks in - Most of us are tired but not fatigued. We do not meet the criteria for fatigue as it is traditionally defined in physiological research (Alan Light - CFSAC; Oct, 2010). Fatigue as it is used by the CDC in their name "CFS" is done so in the most general poorly defined popular sense (and in a manner that is consistent with depression). Those of us that meet the Canadian Consensus Dx criteria couldn't get into a CDC study (quite literally for the life of us) if we tried.

The best outcome of this study would be if it served to move the focus off of fatigue and on to the other increasingly well documented biomarkers.
While I agree that fatigue is not a great term, to screen for studies for the time being, researchers are likely to continue to use questionnaires.
And even if the Light study works out, there may be continue to be cases where one wouldn't put people through exercise tests for a study.

The study found that there were lots of problems with most of the fatigue scales.
So this study can be used to say that if researchers are using a questionnaire to help diagnose patients (the Canadian criteria are even questionnaires), the part of the ME/CFS Fatigue Types Questionnaire that asks about post-exertional symptoms e.g.

dead, heavy feeling after starting to exercise;
next day soreness or fatigue after non-strenuous everyday activities;
mentally tired after the slightest effort;
physically drained or sick after mild activity;
and minimum exercise makes you physically tired
can be useful.

Also, even if some people switch to readily used biomarkers, some "bad guys" may not and we can challenge questionnares they use.
 

WillowJ

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Dolphin,

Thanks for the post. I have to say, I'm not surprised by the findings. While I am a huge fan of Jason and his team, I think we're wasting our time focusing on fatigue.

I am going to say this until it sinks in - Most of us are tired but not fatigued. We do not meet the criteria for fatigue as it is traditionally defined in physiological research (Alan Light - CFSAC; Oct, 2010). Fatigue as it is used by the CDC in their name "CFS" is done so in the most general poorly defined popular sense (and in a manner that is consistent with depression). Those of us that meet the Canadian Consensus Dx criteria couldn't get into a CDC study (quite literally for the life of us) if we tried.

The best outcome of this study would be if it served to move the focus off of fatigue and on to the other increasingly well documented biomarkers.

WE MUST STOP USING THE WORD FATIGUE UNLESS WE"RE TALKING ABOUT A CDC DEFINITION OR A CDC STUDY!
I agree that fatigue as usually defined in medicine does NOT describe us. Most medical dictionaries describe fatigue as a tiredness which is not related to physical ability to carry out activity. Obviously that has nothing to do with us, at least not the part that makes us so disabled.

However, I think this is what Jason et al. are getting at here. We don't have the fatigue they (ppl in general, researchers in general) were thinking of. We have a totally different nature of "fatigue."

But I agree with your point, too... yes, let's not say fatigue.

Last time I did that in my doctor's office, though (insisted I had weakness rather than fatigue), she diagnosed me with "tiredness" and didn't credit my CFS diagnosis. On the other hand, maybe that's a useful diagnosis in the pre-legitimate era for ME/CFS.

If she was using 780.79, that's

*Weakness; lack of energy and strength.
*Physical weakness, lack of strength and vitality, or a lack of concentration.
*Exhaustion that interferes with physical and mental activities.
state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.
*An overwhelming sustained sense of exhaustion and decreased capacity for physical and mental work at usual level
*That state, following a period of mental or bodily activity, characterized by a lessened capacity for work and reduced efficiency of accomplishment, usually accompanied by a feeling of weariness, sleepiness, or irritability.