Thresholds for recovery were set very very "low" (perhaps the bottom percentile and 5th lowest percentile of the healthy adult population on the two scales used)
Tom Kindlon, Irish ME/CFS Association - for Information, Support & Research
23 January 2009
The thresholds for recovery seem very very low:
"Patients were defined as being CSI at post treatment if they had a reliable change index > 1.96 on the CIS fatigue severity subscale [22], a fatigue severity score <= 35 and a Rand-36 physical functioning score > = 65".
Many of the patients already likely had a "physical functioning score >=65" given the mean (SD) values before treatment were: "Physical impairment (Rand 36) 54.0(23.4)"
And the threshold for recovery was only 0.47 SDs above the initial mean score.
I am aware of the questions on the SF-36 PF subscale (scores can range from 0 to 100 with the higher the score, the better their "physical functionaling") and I don't believe most healthy adults would believe scoring 65 on the SF-36 PF scale would mean they were recovered.
As a study[1], that was co-written by one of the authors of this study (Gijs Bleijenberg), pointed out, a community study found that "healthy adults without a chronic condition" had "a mean score of 93.1 (SD 11.7)." The authors of that study[1] pointed out they did not know the exact distribution of the SF-36 subscales - they just made the assumption that the mean - 1SD would represent a threshold for the 85th percentile and rounded this figure to 80.
The threshold in the current study is 65. That is 2.4 SDs below the healthy population's mean score. If the same assumptions were made (i.e. that the curve was normally distributed), this would represent the bottom percentile!
For the CIS fatigue severity subscale (where the possible scores are 8-56 with the higher the score, the greater the fatigue), that same study that Gijs Bleijenberg co-wrote[2] used (to calculate thresholds i.e. from another study) a "normal group of 53 healthy adults with a mean age of 37.1 (SD 11.5)" who had "a mean score on the CIS-fatigue of 17.3 (SD 10.1)."[3]
The ages of those healthy adults are similar to the ages of the CFS patients in this study: Mean (SD) 38.1 (10.2).
In that study[1], they estimated that the 85th percentile (mean+1SD) would be 27 (due to rounding). This study uses 35 or the mean + 1.7525SD or the 95th percentile.
Put another way, patients in this study could be considered recovered if they scored in the bottom percentile on the physical functioning subscale (of the SF-36) and in the 5th lowest percentile on the CIS-fatigue scale!
Tom Kindlon
[1] Knoop H, Bleijenberg G, Gielissen MF, van der Meer JW, White PD. Is a full recovery possible after cognitive behavioural therapy for chronic fatigue syndrome? Psychother Psychosom. 2007;76(3):171-6.
[2] Aaronson NK, Muller M, Cohen PD, Essink-Bot ML, Fekkes M, Sanderman R, Sprangers MA, te Velde A, Verrips E: Translation, validation, and norming of the Dutch language version of the SF-36 Health Survey in community and chronic disease population. J Clin Epidemiol 1998; 51: 1055-1068.
[3] Vercoulen JHMM, Alberts M, Bleijenberg G: De Checklist Individual Strength (CIS) (The Checklist Individual Strength). Gedragstherapie (Behavioural Therapy) 1999; 32: 642-649.
Thresholds for recovery were set very very "low" (perhaps the bottom percentile and 5th lowest percentile of the healthy adult population on the two scales used)
23 January 2009
The thresholds for recovery seem very very low:
"Patients were defined as being CSI at post treatment if they had a reliable change index > 1.96 on the CIS fatigue severity subscale [22], a fatigue severity score <= 35 and a Rand-36 physical functioning score > = 65".
Many of the patients already likely had a "physical functioning score >=65" given the mean (SD) values before treatment were: "Physical impairment (Rand 36) 54.0(23.4)"
And the threshold for recovery was only 0.47 SDs above the initial mean score.
I am aware of the questions on the SF-36 PF subscale (scores can range from 0 to 100 with the higher the score, the better their "physical functionaling") and I don't believe most healthy adults would believe scoring 65 on the SF-36 PF scale would mean they were recovered.
As a study[1], that was co-written by one of the authors of this study (Gijs Bleijenberg), pointed out, a community study found that "healthy adults without a chronic condition" had "a mean score of 93.1 (SD 11.7)." The authors of that study[1] pointed out they did not know the exact distribution of the SF-36 subscales - they just made the assumption that the mean - 1SD would represent a threshold for the 85th percentile and rounded this figure to 80.
The threshold in the current study is 65. That is 2.4 SDs below the healthy population's mean score. If the same assumptions were made (i.e. that the curve was normally distributed), this would represent the bottom percentile!
For the CIS fatigue severity subscale (where the possible scores are 8-56 with the higher the score, the greater the fatigue), that same study that Gijs Bleijenberg co-wrote[2] used (to calculate thresholds i.e. from another study) a "normal group of 53 healthy adults with a mean age of 37.1 (SD 11.5)" who had "a mean score on the CIS-fatigue of 17.3 (SD 10.1)."[3]
The ages of those healthy adults are similar to the ages of the CFS patients in this study: Mean (SD) 38.1 (10.2).
In that study[1], they estimated that the 85th percentile (mean+1SD) would be 27 (due to rounding). This study uses 35 or the mean + 1.7525SD or the 95th percentile.
Put another way, patients in this study could be considered recovered if they scored in the bottom percentile on the physical functioning subscale (of the SF-36) and in the 5th lowest percentile on the CIS-fatigue scale!
Tom Kindlon
[1] Knoop H, Bleijenberg G, Gielissen MF, van der Meer JW, White PD. Is a full recovery possible after cognitive behavioural therapy for chronic fatigue syndrome? Psychother Psychosom. 2007;76(3):171-6.
[2] Aaronson NK, Muller M, Cohen PD, Essink-Bot ML, Fekkes M, Sanderman R, Sprangers MA, te Velde A, Verrips E: Translation, validation, and norming of the Dutch language version of the SF-36 Health Survey in community and chronic disease population. J Clin Epidemiol 1998; 51: 1055-1068.
[3] Vercoulen JHMM, Alberts M, Bleijenberg G: De Checklist Individual Strength (CIS) (The Checklist Individual Strength). Gedragstherapie (Behavioural Therapy) 1999; 32: 642-649.
Competing interests
No competing interests