On 2013 Dec 18, Tom Kindlon commented:

Chalder Fatigue Scale scores: there appear to be at least two errors, possibly more

There appears to be at least two errors in the abstract which are repeating errors from Table 3. The median must be within the range.

So the following two results are impossible: "deteriorated significantly when subjects were given simulated iso-calorific chocolate (CLF/CP) [ 28.5 (17 - 20)vs. 34.5 (13-26)".

There may be other errors but I cannot be 100% sure. There are two versions of the Chalder Fatigue Scale: the original 14-question version and the version that is more widely used in CFS research now, the 11-question version. The authors appear to be using the 11-question version as they say "Subjects having severe fatigue of at least 10 out of 11 on the Chalder Fatigue Scale (binary scored) were enrolled [11]." They also say they are using the likert version. For the 11-question version, the range of possible scores is 0-33. However there are values given greater than 33 in the abstract (which is taken from Table 3) e.g. 34.5, 35 and 38.

If the authors could post the correct information and reply to the point(s) in paragraph 2, it would be appreciated.

On 2013 Oct 29, Tom Kindlon commented:

The authors say, "As this was a proof of concept study; physical activity was not formally assessed. Biochemical markers including plasma polyphenol levels and inflammatory markers were not measured as part of the study as all of the baseline parameters prior to the study were normal, in accord with the criteria for the diagnosis of chronic fatigue syndrome."

The authors are presumably referring to the fact that the Fukuda definition¹ requires researchers to exclude patients with medical or psychiatric disorders that could explain the chronic fatigue and other symptoms. However it is not the case that no abnormalities will ever be found in CFS (plenty have been) nor that the definition encourages researchers not to track biological markers.

Reference:

[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. International Chronic Fatigue Syndrome Study Group. Ann Intern Med 1994, 121(12):953-959.

On 2013 Oct 29, Tom Kindlon commented:

The authors say, "As this was a proof of concept study; physical activity was not formally assessed. Biochemical markers including plasma polyphenol levels and inflammatory markers were not measured as part of the study as all of the baseline parameters prior to the study were normal, in accord with the criteria for the diagnosis of chronic fatigue syndrome."

The authors are presumably referring to the fact that the Fukuda definition¹ requires researchers to exclude patients with medical or psychiatric disorders that could explain the chronic fatigue and other symptoms. However it is not the case that no abnormalities will ever be found in CFS (plenty have been) nor that the definition encourages researchers not to track biological markers.

Reference:

[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. International Chronic Fatigue Syndrome Study Group. Ann Intern Med 1994, 121(12):953-959.

On 2013 Dec 18, Tom Kindlon commented:

Chalder Fatigue Scale scores: there appear to be at least two errors, possibly more

There appears to be at least two errors in the abstract which are repeating errors from Table 3. The median must be within the range.

So the following two results are impossible: "deteriorated significantly when subjects were given simulated iso-calorific chocolate (CLF/CP) [ 28.5 (17 - 20)vs. 34.5 (13-26)".

There may be other errors but I cannot be 100% sure. There are two versions of the Chalder Fatigue Scale: the original 14-question version and the version that is more widely used in CFS research now, the 11-question version. The authors appear to be using the 11-question version as they say "Subjects having severe fatigue of at least 10 out of 11 on the Chalder Fatigue Scale (binary scored) were enrolled [11]." They also say they are using the likert version. For the 11-question version, the range of possible scores is 0-33. However there are values given greater than 33 in the abstract (which is taken from Table 3) e.g. 34.5, 35 and 38.

If the authors could post the correct information and reply to the point(s) in paragraph 2, it would be appreciated.