Pace - analysis dump

Esther12

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Just started this page as a test to see how the wiki can be used for collating analysis of the Pace report.

I'm going to post up something I started writing... decided was no good and gave up upon. Feel free to delete it all, change radically, or ignore completely. This is just to get us started:

Paces abnormal normals

What was planned from the Pace Protocol:

http://www.biomedcentral.com/1471-2377/7/6
Inclusion criteria
1. Both participant and clinician agree that randomisation is acceptable.
2. The participant has given written informed consent.
3. The participant meets operationalised Oxford research diagnostic criteria for CFS [2].
4. The participant's Chalder Fatigue Questionnaire score is 6 or more [27].
5. The participant's SF-36 physical function sub-scale score [28] is 65 or less.
6. The participant is aged at least 18 years old.

The SF-36 physical function sub-scale [29] measures physical function, and has often been used as a primary outcome measure in trials of CBT and GET. We will count a score of 75 (out of a maximum of 100) or more, or a 50% increase from baseline in SF-36 sub-scale score as a positive outcome. A score of 70 is about one standard deviation below the mean score (about 85, depending on the study) for the UK adult population [51,52].
4. "Recovery" will be defined by meeting all four of the following criteria: (i) a Chalder Fatigue Questionnaire score of 3 or less [27], (ii) SF-36 physical Function score of 85 or above [47,48], (iii) a CGI score of 1 [45], and (iv) the participant no longer meets Oxford criteria for CFS [2], CDC criteria for CFS [1] or the London criteria for ME [40].

The final paper classed patients who had been successfully returned to the normal range (promoted as 'back to normal' to the media) as those with a Chalder fatigue score of 18 or less (but different scoring v. approximately 9 or less by bimodal scoring?), and a physical function score of 60 or more. This was the closest we were given to figures for recovery:

A clinically useful difference between the means of the primary outcomes was defined as 0.5 of the SD of these measures at baseline [31], equating to 2 points for Chalder fatigue questionnaire and 8 points for short form-36. A secondary post-hoc analysis compared the proportions of participants who had improved between baseline and 52 weeks by 2 or more points of the Chalder fatigue questionnaire, 8 or more points of the short form-36, and improved on both. In another post-hoc analysis, we compared the proportions of participants who had scores of both primary outcomes within the normal range at 52 weeks. This range was defined as less than the mean plus 1 SD scores of adult attendees to UK general practice of 14.2 (+4.6) for fatigue (score of 18 or less) and equal to or above the mean minus 1 SD scores of the UK working age population of 84 (24) for physical function (score of 60 or more).32,33

31 Guyatt GH, Osaba D, Wu AW, et al. Methods to explain the clinical significance of health status measures. Mayo Clinic Proceedings 2002; 77: 37183.

32 Cella M, Chalder T. Measuring fatigue in clinical and community settings. J Psychosom Res 2010; 69: 1722.

33 Bowling A, Bond M, Jenkinson C, Lamping DL. Short form 36 (SF-36) health survey questionnaire: which normative data should be used? Comparisons between the norms provided by the Omnibus Survey in Britain, The Health Survey for England and the Oxford Healthy Life Survey. J Publ Health Med 1999, 21: 25570.
Lets follow the trail for the normal figures for the Chalder fatigue scale:

From 32 Cella M, Chalder T. Measuring fatigue in clinical and community settings. J Psychosom Res 2010; 69: 1722.

General population participants were registered with five group general practices in the southeast of England chosen to ensure a mix of social class and urban vs. rural distribution. As family doctors in the UK are free of charge, all residents have the right to register. Recruiting representative community samples from general practitioner's lists is a widely used method. Thirty-one thousand, six hundred and fifty-one men and women aged 1845 registered with the five general practices were asked to take part in the original study (Stage 1) (see Ref. [3]). For this current study, only completed data from those who went to see their general practitioner the following year with either a viral illness or a complaint other than a viral illness were used in this study. More detailed description of the sample and recruitment procedures is reported elsewhere (Stage 2) (see Refs.[18,19]). The 1615 patients used for this study are those who completed all the items of the fatigue scale. Aside from knowing that participants presented to the GP with either an infection or another complaint, no further information regarding medical condition, illness, and general practitioner attendance was sought.
[18] Chalder T, Power MJ, Wessely S. Chronic fatigue in the community: a question of attribution. Psychol Med 1996;26: 791800.

[19] Wessely S, Chalder T, Hirsch S, Pawlikowska T, Wallace P, Wright DJ. Postinfectious fatigue: prospective cohort study in primary care. Lancet 1995;345:13338.
The questionnaire begins:

We would like to know more about any problems you have had with feeling tired, weak or lacking in energy in the last month. Please answer ALL the questions by ticking the answer which applies to you most closely. If you have been feeling tired for a long while, then compare yourself to how you felt when you were last well. Please tick only one box per line.
So of the 31651 people asked to fill out this form, we ended up with results from 1615 5%

Much of the loss would have been due to patients not bothering to fill in the form. Would those who have some fatigue problems be any more likely to fill in a form about fatigue than others? Hard to say. Also, anyone healthy enough to not need to see their doctor for a year was excluded. Anyone healthy enough to not bother registering with a doctor would be excluded by default. So this is certainly not a healthy population.

(Im afraid that I dont understand their referencing of papers 18 + 19. 19 is available here: http://qjmed.oxfordjournals.org/content/99/1/49.full and doesnt seem remotely helpful for explaining their decisions here, nor did the abstract for 18).


Now the SF-36 physical function sub-scale score from:

33 Bowling A, Bond M, Jenkinson C, Lamping DL. Short form 36 (SF-36) health survey questionnaire: which normative data should be used? Comparisons between the norms provided by the Omnibus Survey in Britain, The Health Survey for England and the Oxford Healthy Life Survey. J Publ Health Med 1999, 21: 25570.

Available free: http://jpubhealth.oxfordjournals.org/content/21/3/255.full.pdf+html

Table 1 presents the health of the sample: 22% have long term health problems and 16% have acute health problems.

(This is where I gave up - my head swimming with statistics.)