An "improvement" of 2 points for fatigue could also indicate a worsening, depending on how the CFQ is interpreted (which I've discussed elsewhere).
@Lucibee Table 3 in the supplementary material to Collin and Crawley’s 2017 paper demonstrates exactly the effect you suggest, where a decrease of 2 points on the Chalder Fatigue Questionnaire, used in PACE as indicating improvement in fatigue, can occur when the patient has deteriorated.
The patients who reported themselves “very much worse” (n=11) at 1 year follow-up after specialist treatment had a mean change in their Chalder Fatigue Questionnaire score of -2.27, with 95% CI of -4.77, 0.22.
The patients who reported themselves “much worse” (n=23) at 1 year follow-up after specialist treatment had a mean change in their CFQ score of -0.26, but the 95% CI was -2.81, 2.29.
Similarly, the 95% CI for those who reported themselves “a little worse” also includes -2:
The patients who reported themselves “a little worse” (n=51) at 1 year follow-up after specialist treatment had a mean change in their Chalder Fatigue Questionnaire score of -1.24, with 95% CI of -3.08, 0.61.
The patients who reported themselves “no change” (n=65) at 1 year follow-up after specialist treatment had a mean change in their CFQ score of -2.28, with 95% CI of -3.59, -0.96.
It is only when patients reported themselves better that we leave the -2 realm, with mean changes in their CFQ scores of:
A little better (n=157) -5.90
Much better (n=92) -11.0
Very much better (n=25) -14.9
I can’t find a way of linking to the supplementary material or copying the relevant row of the table – but it’s well worth a look.
The Collin and Crawley 2017 paper is here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5513420/
Please do check the original source before quoting these figures or interpretation as I have brain fog!
Someone with number skills could look at the FOI dataset from PACE and create a table showing how the PACE data compare to this. Mean change in Chalder Fatigue scores at 52 weeks according to patient-rated Clinical Global Impression scores. Any takers? I think we'd expect bigger changes, but the pattern/trend seems likely to be in the PACE data too.