On 2014 Jan 08, Tom Kindlon commented:

Questioning the use of the Role Emotional (RE) subscale of the SF-36 questionnaire in the diagnosis of CFS

As background to my previous comment, I thought I'd point out that if people would like to see what makes up the Role Emotional (RE) subscale of the SF-36, a copy of a sample SF-36 questionnaire can be seen at: https://clinicalresearch.ccf.org/fsgs/docs/WEBdocs/Form36.pdf .It is question 14 i.e. 3 questions with only yes or no as possible answers.

The cut off point used in the current study is less than or equal to a score of 66 [1], so two "yes" answers (out of the three questions) is the cut off point for functional impairment.

References:

[1] Chronic Fatigue Syndrome – A clinically empirical approach to its definition and study. William C Reeves, Dieter Wagner, Rosane Nisenbaum, James F Jones, Brian Gurbaxani, Laura Solomon, Dimitris A Papanicolaou, Elizabeth R Unger, Suzanne D Vernon and Christine Heim BMC Medicine 2005, 3:19 doi:10.1186/1741-7015-3-19 http://www.biomedcentral.com/1741-7015/3/19

On 2014 Jan 08, Tom Kindlon commented:

Does the use of the "Role emotional" subscale of the SF-36 help with sensitivity and specificity rates? Can we find out the prevalence rate if this subscale hadn't been used?

It is to be welcomed that attempts are being made to operationalize the CDC (94) CFS criteria [1], enabling easier comparisons between studies and making it easier for researchers to try to replicate findings. So, for example, having some sort of numerical value on a symptom so that one can say whether a symptom is present or not in a patient seems to be a good idea.

However, if one is aiming to do this, it would seem preferable to choose methods that have good sensitivity and specificity rates for the condition in question. And it's questionnable whether the methods used in this study have good sensitivity and specificity.

The authors claim that they "used stringent (i.e., <= 25th percentile population norms on any of the 4 SF-36 scales) to define severe functional impairment". One of the SF-36 subscales in question is the "role emotional" subscale. This involves questions such as: "During the past 4 weeks, have you accomplished less than you would like as a result of any emotional problems?" Does this really capture whether there has been a "substantial reduction in previous levels of .. personal activities"? [Full quote from paper[1]: 1) clinically evaluated, unexplained, persistent or relapsing chronic fatigue that is of new or definite onset [has not been lifelong]; is not the result of ongoing exertion; is not substantially alleviated by rest; and results in substantial reduction in previous levels of occupational, educational, social, or personal activities] Perhaps the other three sub-scales cover this? For example, a better measure of whether the condition is having an effect on somebody's "personal activities" might be got from using the physical functioning subscales which asks about ability to walk distances, bath or dress oneself, etc. If this score is low, it's likely one's ability to do "personal activities" has been impaired.

Baraniuk[2] used the CDC '94 not operationalized in the same way as this study and found that CFS patients scores did have lower scores on some of the SF-36 subscales - but role emotional was one of the ones that weren't different (the others that weren't different were mental health and general health change). Would it be possible for the authors to calculate the all important overall prevalence rate if those people who only satisfied this part of the "functional impairment" criteria are excluded? This data would be be useful not just in the US but around the world - countries around the world have been depending on the US to undertake such large scale (and expensive) studies on CFS.

Even before the recent broadening of the criteria, it had been felt by some that the CDC '94 criteria lacked specificity. For example, Kennedy[3] investigated "patients with self-reported symptoms which developed sporadically (sCFS, n=48); after Gulf War service (GW, n=24); and following exposure to organophosphate insecticides (OP, n=25)" all of whom fulfilled the CDC '94 criteria[1]. Based on their findings, they concluded that "differences in simple, easily performed clinical outcome measurements can be observed between groups of patients, all of whom fulfill the CDC-1994 criteria for CFS. It is likely that their response to treatment may also vary. The specificity of the CFS case definition should be improved to define more homogeneous groups of patients for the purposes of treatment and research."

Perhaps what is required is a totally new set of criteria?

References:

[1] Fukuda, K., Straus, S.E., Hickie, I., Sharpe, M.C., Dobbins, J.G., & Komaroff, A. (1994). The chronic fatigue syndrome: A comprehensive approach to its definition and study. Annals of Internal Medicine, 121 (12):953-959. http://www.annals.org/cgi/content/full/121/12/953

[2] James N Baraniuk, Begona Casado, Hilda Maibach, Daniel J Clauw, Lewis K Pannell and Sonja Hess S. A chronic fatigue syndrome - related proteome in human cerebrospinal fluid. BMC Neurology 2005, 5:22 doi:10.1186/1471-2377-5-22http://www.biomedcentral.com/1471-2377/5/22

[3] Kennedy G, Abbot NC, Spence V.A, Underwood C, Belch JJF. The specificity of the CDC-1994 criteria for chronic fatigue syndrome: comparison of health status in three groups of patients who fulfil the criteria. Ann Epidemiol 2004; 14: 95–100.

On 2014 Jan 08, Tom Kindlon commented:

Does the use of the "Role emotional" subscale of the SF-36 help with sensitivity and specificity rates? Can we find out the prevalence rate if this subscale hadn't been used?

It is to be welcomed that attempts are being made to operationalize the CDC (94) CFS criteria [1], enabling easier comparisons between studies and making it easier for researchers to try to replicate findings. So, for example, having some sort of numerical value on a symptom so that one can say whether a symptom is present or not in a patient seems to be a good idea.

However, if one is aiming to do this, it would seem preferable to choose methods that have good sensitivity and specificity rates for the condition in question. And it's questionnable whether the methods used in this study have good sensitivity and specificity.

The authors claim that they "used stringent (i.e., <= 25th percentile population norms on any of the 4 SF-36 scales) to define severe functional impairment". One of the SF-36 subscales in question is the "role emotional" subscale. This involves questions such as: "During the past 4 weeks, have you accomplished less than you would like as a result of any emotional problems?" Does this really capture whether there has been a "substantial reduction in previous levels of .. personal activities"? [Full quote from paper[1]: 1) clinically evaluated, unexplained, persistent or relapsing chronic fatigue that is of new or definite onset [has not been lifelong]; is not the result of ongoing exertion; is not substantially alleviated by rest; and results in substantial reduction in previous levels of occupational, educational, social, or personal activities] Perhaps the other three sub-scales cover this? For example, a better measure of whether the condition is having an effect on somebody's "personal activities" might be got from using the physical functioning subscales which asks about ability to walk distances, bath or dress oneself, etc. If this score is low, it's likely one's ability to do "personal activities" has been impaired.

Baraniuk[2] used the CDC '94 not operationalized in the same way as this study and found that CFS patients scores did have lower scores on some of the SF-36 subscales - but role emotional was one of the ones that weren't different (the others that weren't different were mental health and general health change). Would it be possible for the authors to calculate the all important overall prevalence rate if those people who only satisfied this part of the "functional impairment" criteria are excluded? This data would be be useful not just in the US but around the world - countries around the world have been depending on the US to undertake such large scale (and expensive) studies on CFS.

Even before the recent broadening of the criteria, it had been felt by some that the CDC '94 criteria lacked specificity. For example, Kennedy[3] investigated "patients with self-reported symptoms which developed sporadically (sCFS, n=48); after Gulf War service (GW, n=24); and following exposure to organophosphate insecticides (OP, n=25)" all of whom fulfilled the CDC '94 criteria[1]. Based on their findings, they concluded that "differences in simple, easily performed clinical outcome measurements can be observed between groups of patients, all of whom fulfill the CDC-1994 criteria for CFS. It is likely that their response to treatment may also vary. The specificity of the CFS case definition should be improved to define more homogeneous groups of patients for the purposes of treatment and research."

Perhaps what is required is a totally new set of criteria?

References:

[1] Fukuda, K., Straus, S.E., Hickie, I., Sharpe, M.C., Dobbins, J.G., & Komaroff, A. (1994). The chronic fatigue syndrome: A comprehensive approach to its definition and study. Annals of Internal Medicine, 121 (12):953-959. http://www.annals.org/cgi/content/full/121/12/953

[2] James N Baraniuk, Begona Casado, Hilda Maibach, Daniel J Clauw, Lewis K Pannell and Sonja Hess S. A chronic fatigue syndrome - related proteome in human cerebrospinal fluid. BMC Neurology 2005, 5:22 doi:10.1186/1471-2377-5-22http://www.biomedcentral.com/1471-2377/5/22

[3] Kennedy G, Abbot NC, Spence V.A, Underwood C, Belch JJF. The specificity of the CDC-1994 criteria for chronic fatigue syndrome: comparison of health status in three groups of patients who fulfil the criteria. Ann Epidemiol 2004; 14: 95–100.

On 2014 Jan 08, Tom Kindlon commented:

Questioning the use of the Role Emotional (RE) subscale of the SF-36 questionnaire in the diagnosis of CFS

As background to my previous comment, I thought I'd point out that if people would like to see what makes up the Role Emotional (RE) subscale of the SF-36, a copy of a sample SF-36 questionnaire can be seen at: https://clinicalresearch.ccf.org/fsgs/docs/WEBdocs/Form36.pdf .It is question 14 i.e. 3 questions with only yes or no as possible answers.

The cut off point used in the current study is less than or equal to a score of 66 [1], so two "yes" answers (out of the three questions) is the cut off point for functional impairment.

References:

[1] Chronic Fatigue Syndrome – A clinically empirical approach to its definition and study. William C Reeves, Dieter Wagner, Rosane Nisenbaum, James F Jones, Brian Gurbaxani, Laura Solomon, Dimitris A Papanicolaou, Elizabeth R Unger, Suzanne D Vernon and Christine Heim BMC Medicine 2005, 3:19 doi:10.1186/1741-7015-3-19 http://www.biomedcentral.com/1741-7015/3/19