This is an interesting study. However, the issue of the use of
appropriate outcome measures is an important one in
the area of Chronic Fatigue Syndrome (CFS) research. Problems have been
reported with the use of self-report outcome measures.
An earlier Nijmegen team incl. Gijs Bleijenberg (one of the co-
authors) investigated this area[1]: "It is not clear whether subjective
accounts of physical activity level adequately reflect the actual level of
physical activity. Therefore the primary aims of the present study were to
assess actual activity level in patients with CFS to validate claims of
lower levels of physical activity and to validate the reported
relationship between fatigue and activity level that was found on self-
report questionnaires. In addition, we evaluated whether physical activity
level adequately can be assessed by self-report measures. An Accelerometer
was used as a reference for actual level of physical activity.". The
authors reported on the correlations on 7 outcome measures in relation to
the
actometer readings: "none of the self-report questionnaires had strong
correlations with the Actometer. Thus, self-report questionnaires are no
perfect parallel tests for the Actometer." The authors pointed out that
"the subjective instruments do not measure actual behaviour. Responses on
these instruments appear to be an expression of the patients' views about
activity and may be biased by cognitions concerning illness and
disability." This was
re-iterated in another paper from a different Nijmegen team involving Gijs
Bleijenberg[2]: "In earlier studies of our research group, actual motor
activity has been recorded with an ankle-worn motion-sensing device
(actometer) in conjunction with self-report measures of physical activity.
The data of these studies suggest that self-report measures of activity
reflect the patients' view about their physical activity and may have been
biased by cognitions concerning illness and disability."
It is thus disappointing that in this current study actometers were
not either not reported or not used following the intervention. The
authors do report that they had used actometers before the intervention:
"In the original trial, 2 treatment protocols were used: 1 for patients
with a passive physical activity pattern and 1 for relatively active
patients. The physical activity pattern of the adolescent patient with CFS
was measured with an actometer, a motion-sensing device attached to the
ankle."
A recent uncontrolled study[3] highlights the problems that can occur
with self-report measures following CBT for CFS. It involved testing a
form Cognitive Behavior Therapy (CBT) for CFS which included encouraging
patients to go for longer walks. It found that on the SF-36 Physical
Functioning (PF) scale, patients improved from a pre-treatment mean (SD)
of 49.44 (25.19) to 58.18 (26.48) post-treatment, equivalent to a Cohen's
d value of 0.35. On the Fatigue Severity Scale (FSS), the improvement as
measured by the cohen's d value was even great (0.78) from an initial pre-
treatment mean (SD) of 5.93 (0.93) to a 5.20
(0.95) post-treatment.
However on actigraphy there was actually a numerical decrease from a
pre-treatment mean (SD) of 224696.90 (158389.64) to 203916.67 (122585.92)
post-treatment (cohen's d: -0.13). So just because patients report lower
fatigue and better scores on the SF-36 PF scale, it does not mean they are
doing more, which is what GET and CBT based on GET claim to bring about.
These results seem particularly pertinent given two of the three primary
outcome measures in this study are the SF-36 PF scale and a fatigue scale.
Being able to work full-time probably involves a reasonable test of
somebody's functioning.
However the usefulness of CBT to bring about improvement in hours
worked is far from clear. For example, another Dutch study of CBT
reported a recovery rate of 37%[4]. It used the following definition for
recovery: "Patients were defined as being CSI at post treatment if they
had a reliable change index > 1.96 on the CIS fatigue severity
subscale, a fatigue severity score <= 35 and a Rand-36 physical
functioning score > = 65". However, the improvement with regards to
hours worked was much smaller. Before the intervention, participants
worked an average of 9.4 hours (standard deviation: 13.5); after the
intervention, they worked 11.4 hours (standard deviation: 14.7), a non-
significant change. The median number of contracted hours before the
intervention was 10 hours;
after it was 7 hours. In the discussion section, the authors point that
fewer participants had a paid job following the intervention than before.
Attendance at school is probably not as good a measure of functioning
as hours worked. Education systems do not generally base assessments of a
child's performance on the number of days they attend! Instead, they use
measures such as outcomes in examinations. Charities for ME and CFS can
encourage some children that some sort of education at home may be more
beneficial for both their health and also their education[5] than
attendance at school. CBT can encourage school attendance but by itself,
attendance at school should not necessarily be seen as successful
result in itself if, for example, the children are not learning that much
or are under-performing relative to their ability[6].
However if, as the authors may do, one believes that full attendance
at school is a good measure of activity and functioning, it would have
been good if the paper had presented data on the number and/or percentage
of participants who had "clinically significant improvement" on all three
of the outcome measures. As I pointed out earlier, following CBT, CFS
patients who report lower fatigue and/or better physical functioning may
not actually be doing more. Similarly, participants could be attending
work or school full-time but still have ongoing problems with fatigue.
It is slightly disappointing that we did not see some data:
"Data on the type of activities of patients at the time of
the follow-up assessment were not available for all of the
patients. Some patients only indicated on the questionnaires
that they did not study and did not work. We decided not to impute these
missing values, because more detailed information about their activities
were lacking. This could have introduced a bias when determining the long-
term effects of CBT on work and/or school attendance. An example of such a
bias would be that these patients are less active and function at a lower
level than the patients who indicated that they worked or attended school,
which, in turn, might have led to an overestimation of the effect of CBT."
Should we assume from this that the percentage with full school/work
attendance following CBT is not 29/42 but 29/50 (58%), the same number as
at the final assessment following CBT? Data for 50 participants at follow
-up was available for fatigue severity and physical functioning.
One further point to raise is the thresholds for "clinically
significant improvement". For CIS-fatigue, it was a "reliable change
index of >1.96 and a score of <35.7". Another CBT study in the area
co-written by the two of the authors (Knoop & Bleijenberg)[7] referred
to 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)."[8]. The
threshold in the current study of 35.7 is 1.82 standard deviations above
that mean of 17.3. It should also be remembered that the minimum score on
the CIS-fatigue scale is 8 so that 17.3 is only 0.92 standard deviations
above that. Somebody with a fatigue score in the 30s for example still
has significant fatigue.
The same study[7] by two of the authors said that "healthy adults
without a chronic condition" had "a mean score of 93.1 (SD 11.7)" on the
SF-36 physical functioning subscale. The maximum one can score is 100.
Compare that with the threshold of 75 that is sufficient to be seen as
having a "clinically significant improvement" on that scale in the current
study.
References
[1] Vercoulen JH, Bazelmans E, Swanink CM, Fennis JF, Galama JM,
Jongen PJ, Hommes O, Van der Meer JW, Bleijenberg G. Physical activity in
chronic fatigue syndrome: assessment and its role in fatigue. J Psychiatr
Res. 1997 Nov-Dec;31(6):661-73.
[2] van der Werf SP, Prins JB, Vercoulen JH, van der Meer JW,
Bleijenberg G. Identifying physical activity patterns in chronic fatigue
syndrome using actigraphic assessment. J Psychosom Res. 2000 Nov;49(5):373
-9.
[3] Friedberg F, Sohl S. Cognitive-behavior therapy in chronic
fatigue syndrome: is improvement related to increased physical activity? J
Clin Psychol. 2009 Feb 11.
[4] Scheeres K, Wensing M, Bleijenberg G, Severens JL. Implementing
cognitive behavior therapy for chronic fatigue syndrome in mental health
care: a costs and outcomes analysis. BMC Health Serv Res. 2008 Aug
13;8:175.
[5] The Young ME Sufferers Trust http://www.tymestrust.org [Last
accessed: 31st March, 2009]
[6] Van Hoof ELS, De Becker PJ, Lapp C, De Meirleir KL. How do
adolescents with chronic fatigue syndrome perceive their social
environment? A quantitative study. IACFS/ME Spring Bulletin 2009
[7] 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.
[8] 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.
Conflict of Interest:
None declared
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