On 2014 Feb 02, Tom Kindlon commented:

Observations on apparent changes in methods of assessing symptoms

(This was originally posted here: http://www.pophealthmetrics.com/content/3/1/8/comments but the formatting has been removed and some people may not read the paper there either).

I notice that the "Symptom Inventory collects information about the presence, frequency, and intensity of .. symptoms during the month preceding the interview". However the Fukuda et al '94 definition [1] is supposed to look for "the concurrent occurrence of four or more of the following symptoms, all of which must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue".

Was there a particular reason why a time frame of one month was chosen? This would suggest that relatively short-lived symptoms would be counted. If the reasoning was that asking people detailed questions about symptom severity and frequency over a longer period would might not be as accurate, perhaps a two-stage question could be asked: firstly asking whether symptoms "have persisted or recurred during 6 or more consecutive months of illness" and then asking a more detailed question about frequency and intensity.

I also see no mention of the requirement, that was in the initial definition [1], that the symptoms didn't predate the fatigue. Again, if this is a change, it would seem to risk reducing the specificity of the symptom criteria (i.e. increasing the chances that symptoms from other causes are counted) so perhaps again a yes/no question would be good.

References:

[1] Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A: The chronic fatigue syndrome; a comprehensive approach to its definition and study. Ann Int Med 1994, 121:953-959.

On 2014 Feb 02, Tom Kindlon commented:

More symptoms could be added to a CFS Symptom Inventory

(This was originally posted here: http://www.pophealthmetrics.com/content/3/1/8/comments but the formatting has been removed and some people may not read the paper there either).

Many would feel that the 8 symptoms used in the CDC '94 definition [1] were chosen in a somewhat arbitrary fashion; so it is to be welcomed that the CDC itself has started to look beyond these symptoms with the CDC CFS Symptom Inventory. The idea of a Short Form of the CDC Symptom Inventory is also interesting.

However, it is not clear to me where the extra symptoms that are on the CDC CFS Symptom Inventory came from. For example, I didn't see some of the symptoms listed in Reeves et al [2].

In 2001, De Becker et al [3] published data on the symptoms found in over 2500 patients. They tried to improve on the 1988 [4] and 1994 CDC criteria. They suggested a list of symptoms that could be used to strengthen the ability to select ME/CFS patients. Many of the symptoms they mentioned are not in the CDC CFS Symptom Inventory.

So to claim that the "CDC Symptom Inventory assesses the full range of CFS associated symptoms" seems questionable. It would be interesting if in future these symptoms (that De Becker et al were suggesting) were added before statistical analyses are performed. The fatigue criteria and functional impairment criteria have become much less restrictive [5]. For example, to satisfy the fatigue criteria, the fatigue is required to be greater than or equal to the medians of the MFI general fatigue (≥ 13) or reduced activity (≥ 10) scales. So it now seems particularly important that the symptom criteria have good sensitivity and specificity or one is going to end up with a definition that leads to very heterogeneous samples.

References:

[1] Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A: The chronic fatigue syndrome; a comprehensive approach to its definition and study.Ann Int Med 1994, 121:953-959.

[2] Reeves WC, Lloyd A, Vernon SD, Klimas N, Jason LA, Bleijenberg G, Evengard B, White PD, Nisenbaum R, Unger ER, International Chronic Fatigue Syndrome Study Group: Identification of ambiguities in the 1994 chronic fatigue syndrome research case definition and recommendations for resolution.BMC Health Services Research 2003, 3:25.http://dx.doi.org/10.1186/1472-6963-3-25

[3] A definition-based analysis of symptoms in a large cohort of patients withchronic fatigue syndrome, P. De Becker, N. McGregor, and K. De Meirleir.Journal of Internal Medicine 2001;250:234-240

[4] Holmes GP, Kaplan JE, Gantz NM, Komaroff AL, Schonberger LB, Straus SE, et al.: Chronic fatigue syndrome: a working case definition. Ann Intern Med 1988, 108:387-389.

[5] Reeves WC, Wagner D, Nisenbaum R, Jones JF, Gurbaxani B, Solomon L, Papanicolaou DA,Unger ER, Vernon SD, Heim C: Chronic fatigue syndrome — a clinically empirical approachto its definition and study. BMC Medicine 2005, 3:16.

On 2014 Feb 02, Tom Kindlon commented:

More symptoms could be added to a CFS Symptom Inventory

(This was originally posted here: http://www.pophealthmetrics.com/content/3/1/8/comments but the formatting has been removed and some people may not read the paper there either).

Many would feel that the 8 symptoms used in the CDC '94 definition [1] were chosen in a somewhat arbitrary fashion; so it is to be welcomed that the CDC itself has started to look beyond these symptoms with the CDC CFS Symptom Inventory. The idea of a Short Form of the CDC Symptom Inventory is also interesting.

However, it is not clear to me where the extra symptoms that are on the CDC CFS Symptom Inventory came from. For example, I didn't see some of the symptoms listed in Reeves et al [2].

In 2001, De Becker et al [3] published data on the symptoms found in over 2500 patients. They tried to improve on the 1988 [4] and 1994 CDC criteria. They suggested a list of symptoms that could be used to strengthen the ability to select ME/CFS patients. Many of the symptoms they mentioned are not in the CDC CFS Symptom Inventory.

So to claim that the "CDC Symptom Inventory assesses the full range of CFS associated symptoms" seems questionable. It would be interesting if in future these symptoms (that De Becker et al were suggesting) were added before statistical analyses are performed. The fatigue criteria and functional impairment criteria have become much less restrictive [5]. For example, to satisfy the fatigue criteria, the fatigue is required to be greater than or equal to the medians of the MFI general fatigue (≥ 13) or reduced activity (≥ 10) scales. So it now seems particularly important that the symptom criteria have good sensitivity and specificity or one is going to end up with a definition that leads to very heterogeneous samples.

References:

[1] Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A: The chronic fatigue syndrome; a comprehensive approach to its definition and study.Ann Int Med 1994, 121:953-959.

[2] Reeves WC, Lloyd A, Vernon SD, Klimas N, Jason LA, Bleijenberg G, Evengard B, White PD, Nisenbaum R, Unger ER, International Chronic Fatigue Syndrome Study Group: Identification of ambiguities in the 1994 chronic fatigue syndrome research case definition and recommendations for resolution.BMC Health Services Research 2003, 3:25.http://dx.doi.org/10.1186/1472-6963-3-25

[3] A definition-based analysis of symptoms in a large cohort of patients withchronic fatigue syndrome, P. De Becker, N. McGregor, and K. De Meirleir.Journal of Internal Medicine 2001;250:234-240

[4] Holmes GP, Kaplan JE, Gantz NM, Komaroff AL, Schonberger LB, Straus SE, et al.: Chronic fatigue syndrome: a working case definition. Ann Intern Med 1988, 108:387-389.

[5] Reeves WC, Wagner D, Nisenbaum R, Jones JF, Gurbaxani B, Solomon L, Papanicolaou DA,Unger ER, Vernon SD, Heim C: Chronic fatigue syndrome — a clinically empirical approachto its definition and study. BMC Medicine 2005, 3:16.

On 2014 Feb 02, Tom Kindlon commented:

Observations on apparent changes in methods of assessing symptoms

(This was originally posted here: http://www.pophealthmetrics.com/content/3/1/8/comments but the formatting has been removed and some people may not read the paper there either).

I notice that the "Symptom Inventory collects information about the presence, frequency, and intensity of .. symptoms during the month preceding the interview". However the Fukuda et al '94 definition [1] is supposed to look for "the concurrent occurrence of four or more of the following symptoms, all of which must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue".

Was there a particular reason why a time frame of one month was chosen? This would suggest that relatively short-lived symptoms would be counted. If the reasoning was that asking people detailed questions about symptom severity and frequency over a longer period would might not be as accurate, perhaps a two-stage question could be asked: firstly asking whether symptoms "have persisted or recurred during 6 or more consecutive months of illness" and then asking a more detailed question about frequency and intensity.

I also see no mention of the requirement, that was in the initial definition [1], that the symptoms didn't predate the fatigue. Again, if this is a change, it would seem to risk reducing the specificity of the symptom criteria (i.e. increasing the chances that symptoms from other causes are counted) so perhaps again a yes/no question would be good.

References:

[1] Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A: The chronic fatigue syndrome; a comprehensive approach to its definition and study. Ann Int Med 1994, 121:953-959.