- Jul 2018
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europepmc.org europepmc.org
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On 2014 Apr 16, Tom Kindlon commented:
Some comments:
In this study, CFS/ME (or CFS in the abstract) is defined in this extremely strange way:
"Identification of fatigue syndrome cases A list of fatigue syndrome diagnoses was collated from the library of diagnostic codes within the GPRD (Gallagher et al. 2004). Patients aged >16 years with a new fatigue syndrome diagnosis in their records for the calendar years 1988-2001 were identified: only patients with a complete record for the 3 years before the date of diagnosis (the index date) were studied. Two subgroups of fatigue syndrome cases were studied: those with a diagnostic label that included the word ' post-viral ' or ' post-infectious ', which we call PVFS here, and the remainder, composed of CFS or ME, which we call CFS/ME."
Peter White (the corresponding author) knows that this is not how CFS/ME is defined of course (i.e. CFS/ME includes many post-viral or post-infectious cases).
Most of the paper actually isn't about comparing the PVFS group vs the CFS/ME and there is no table given for making the comparison. We just really have the text:
"Differences in risk markers between the two subgroups of fatigue syndrome, CFS/ME and PVFS, were assessed by testing for interaction terms in the models presented in Table 3. The presence of prior fatigue symptoms or prior depressive disorders was more common in patients labelled with CFS/ME. Prior infections, particularly viral ones (but not influenza), were more common in patients labelled with PVFS. The interaction terms all had p values of <0.001 in likelihood ratio tests, except for depressive disorder in the fatigue syndrome versus OA analysis, where p=0.04. The multivariable models for CFS are presented in Table 4. Fatigue and depressive disorders predicted CFS in both models, but different recent infections differentiated CFS from IBS in particular."
Discussion: "The data also suggested that there are subgroup differences in the risks for particular fatigue syndromes. The symptom of fatigue, mood and symptom- based diagnoses were all specific risks for a diagnosis of CFS/ME compared to PVFS, whereas almost all infectious groups were specific to PVFS in contrast to CFS/ME. CFS/ME was more similar to IBS than PVFS with regard to its risk markers. Even so, depressive diagnoses were a greater long-term risk marker for CFS/ME than IBS, and, as expected, systemic and gut infections also differentiated the two syndromes."
Just before the very end of the paper, they come out with this: "These data also suggest that fatigue syndromes are heterogeneous (Vollmer-Conna et al. 2006), and that CFS/ME and PVFS should be considered as separate conditions, with CFS/ME having more in common with IBS than PVFS does (Aggarwal et al. 2006). This requires revision of the ICD-10 taxonomy, which classifies PVFS with ME (WHO, 1992). The duration of PVFS of the same patients in this study was considerably less than CFS/ME, supporting this distinction (Hamilton et al. 2005)." [Remember PVFS is the group where a GP said it was a post-viral or post-infectious case and CFS/ME are the other cases. The paper doesn't even mention that CFS is linked to G93:3 or even that he's talking about G93;3]
One basic flaw is that all this shows is that a GP may be more inclined to give a "post-viral" or "post-infectious" diagnosis if they have viewed/"experienced" a patient in a certain way before attending, and give an alternative diagnosis if a patient has already had depressive symptoms (or the GP decided they were depressive symptoms) or fatigue in the past otherwise. It doesn't prove that the actual conditions the patients have are different i.e. it doesn't prove that the symptoms in the second group aren't post-viral/post-infectious.
Also the suggestion that CFS/ME and PVFS be separated by the WHO involves a few assumptions:
It would have to be said that CFS/ME does not include PVFS/Post-infectious fatigue. What they did in the study was define CFS/ME as CFS/ME minus PVFS and minus PIFS.
This was a prospective study. If a patient comes in with symptoms after being ill for 1/2/3+ years of being ill, how would a doctor/other know which WHO category to put the patient in? They would need to show that there was a good objective way of separating patients into either the PVFS/PIFS and CFS/ME (which is CFS/ME minus PVFS/PIFS). They haven't shown this.
This comment, imported by Hypothesis from PubMed Commons, is licensed under CC BY.
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- Feb 2018
-
europepmc.org europepmc.org
-
On 2014 Apr 16, Tom Kindlon commented:
Some comments:
In this study, CFS/ME (or CFS in the abstract) is defined in this extremely strange way:
"Identification of fatigue syndrome cases A list of fatigue syndrome diagnoses was collated from the library of diagnostic codes within the GPRD (Gallagher et al. 2004). Patients aged >16 years with a new fatigue syndrome diagnosis in their records for the calendar years 1988-2001 were identified: only patients with a complete record for the 3 years before the date of diagnosis (the index date) were studied. Two subgroups of fatigue syndrome cases were studied: those with a diagnostic label that included the word ' post-viral ' or ' post-infectious ', which we call PVFS here, and the remainder, composed of CFS or ME, which we call CFS/ME."
Peter White (the corresponding author) knows that this is not how CFS/ME is defined of course (i.e. CFS/ME includes many post-viral or post-infectious cases).
Most of the paper actually isn't about comparing the PVFS group vs the CFS/ME and there is no table given for making the comparison. We just really have the text:
"Differences in risk markers between the two subgroups of fatigue syndrome, CFS/ME and PVFS, were assessed by testing for interaction terms in the models presented in Table 3. The presence of prior fatigue symptoms or prior depressive disorders was more common in patients labelled with CFS/ME. Prior infections, particularly viral ones (but not influenza), were more common in patients labelled with PVFS. The interaction terms all had p values of <0.001 in likelihood ratio tests, except for depressive disorder in the fatigue syndrome versus OA analysis, where p=0.04. The multivariable models for CFS are presented in Table 4. Fatigue and depressive disorders predicted CFS in both models, but different recent infections differentiated CFS from IBS in particular."
Discussion: "The data also suggested that there are subgroup differences in the risks for particular fatigue syndromes. The symptom of fatigue, mood and symptom- based diagnoses were all specific risks for a diagnosis of CFS/ME compared to PVFS, whereas almost all infectious groups were specific to PVFS in contrast to CFS/ME. CFS/ME was more similar to IBS than PVFS with regard to its risk markers. Even so, depressive diagnoses were a greater long-term risk marker for CFS/ME than IBS, and, as expected, systemic and gut infections also differentiated the two syndromes."
Just before the very end of the paper, they come out with this: "These data also suggest that fatigue syndromes are heterogeneous (Vollmer-Conna et al. 2006), and that CFS/ME and PVFS should be considered as separate conditions, with CFS/ME having more in common with IBS than PVFS does (Aggarwal et al. 2006). This requires revision of the ICD-10 taxonomy, which classifies PVFS with ME (WHO, 1992). The duration of PVFS of the same patients in this study was considerably less than CFS/ME, supporting this distinction (Hamilton et al. 2005)." [Remember PVFS is the group where a GP said it was a post-viral or post-infectious case and CFS/ME are the other cases. The paper doesn't even mention that CFS is linked to G93:3 or even that he's talking about G93;3]
One basic flaw is that all this shows is that a GP may be more inclined to give a "post-viral" or "post-infectious" diagnosis if they have viewed/"experienced" a patient in a certain way before attending, and give an alternative diagnosis if a patient has already had depressive symptoms (or the GP decided they were depressive symptoms) or fatigue in the past otherwise. It doesn't prove that the actual conditions the patients have are different i.e. it doesn't prove that the symptoms in the second group aren't post-viral/post-infectious.
Also the suggestion that CFS/ME and PVFS be separated by the WHO involves a few assumptions:
It would have to be said that CFS/ME does not include PVFS/Post-infectious fatigue. What they did in the study was define CFS/ME as CFS/ME minus PVFS and minus PIFS.
This was a prospective study. If a patient comes in with symptoms after being ill for 1/2/3+ years of being ill, how would a doctor/other know which WHO category to put the patient in? They would need to show that there was a good objective way of separating patients into either the PVFS/PIFS and CFS/ME (which is CFS/ME minus PVFS/PIFS). They haven't shown this.
This comment, imported by Hypothesis from PubMed Commons, is licensed under CC BY.
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