The AHRQ Addendum reanalysis evaluated the evidence including all studies including Oxford studies and then after excluding Oxford studies.
The addendum stated:
"This addendum has delineated differences in treatment effectiveness and harms according to case definitions, highlighting studies that used the Oxford (Sharpe, 1991) case definition and how these studies impacted our conclusions.... Our sensitivity analysis would result in a downgrading of our strength of evidence on several outcomes which can be attributed to the decrease in power, dominance of one large trial, or lack of trials using criteria other than the Oxford (Sharpe, 1991) case definition for inclusion. Blatantly missing from this body of literature are trials evaluating effectiveness of interventions in the treatment of individuals meeting case definitions for ME or ME/CFS. "
Examples of the findings for some of the specific measures are below.
In both the initial analysis and the addendum, PACE was evaluated as a good study with no evidence of bias. So this reassessment is not based on a reevaluation of PACE - only on excluding the Oxford studies from the evidence review.
The Addendum gives the following justification for excluding Oxford from the reanalysis
"The Oxford (Sharpe, 1991) case definition is the least specific of the definitions and less generalizable to the broader population of patients with ME/CFS. It could identify individuals who have had 6 months of unexplained fatigue with physical and mental impairment, but no other specific features of ME/CFS such as post-exertional malaise which is considered by many to be a hallmark symptom of the disease.3 As a result, using the Oxford case definition results in a high risk of including patients who may have an alternate fatiguing illness or whose illness resolves spontaneously with time. In light of this, we recommended in our report that future intervention studies use a single agreed upon case definition, other than the Oxford (Sharpe, 1991) case definition...The National Institute of Health (NIH) panel assembled to review evidence presented at the NIH Pathways to Prevention Workshop agreed with our recommendation, stating that the continued use of the Oxford (Sharpe, 1991) case definition “may impair progress and cause harm.”
I would think the same issue applies with the Cochrane reviews although I have not compared the studies in the AHRQ evidence review to those in the Cochrane review.
Details from the review.
CBT - evidence for function improvement: Unlike the positive results of the Oxford based trials, the results of the trials fulfilling the CDC criteria are mixed and would provide insufficient evidence to determine the effectiveness of CBT
CBT - evidence for fatigue improvement: The overall analyses of fatigue outcomes, including the single study using Oxford case definition inclusion criteria, provided low strength of evidence that CBT improves fatigue. In removing the Oxford case definition based study, we are left with four fair-quality studies, three finding benefit (n=327) and one finding no benefit (n=65), and one poor-quality study finding no benefit (n=58). The results are generally consistent with the overall conclusion and would provide low strength of evidence that CBT improves fatigue.
GET - evidence for improvement - The results are consistent across trials with improvement in function, fatigue, and global improvement and provided moderate strength of evidence for improved function and global improvement, low strength of evidence for reduced fatigue and decreased work impairment, and insufficient evidence for improved quality of life (no trials) (Table 7). By excluding the three trials using the Oxford (Sharpe, 1991) case definition for inclusion, there would be insufficient evidence of the effectiveness of GET on any outcome. .
