Questions for the PACE trial PIs
Posted: Mon Aug 19, 2013 9:23 pm
I see that the PACE trial authors have issued a statement that you have put in a locked thread suggesting that they answer questions. Are they also answering questions?
I have some specific questions for them could you put the questions to them or are they only making statements.
1) What mechanism did they use to control for different expectations within the different trial arms. I've read papers saying that
Perspectives on Psychological Science July 2013 8: 445-454, doi:10.1177/1745691613491271
Yet the APT and SMC group to me seem to be setting up different expectations to the CBT and GET group. This is potentially a serious problem due to the reliance on subjective outcome measures. I believe Wechsler's asthma study showed the dangers of relying on subjective measures where they showed a placebo effect with the subjective measures but not objective ones,
Hence the question how do you know that its not just different levels of placebo effect based on different expectations being measured.
2) In their recovery paper they justify changing the threshold on the short form 36 physical function scale from 85 to 60 with the claim that half the working age population scores under 85. They quote a paper by bowling which is based on the 1992 OPCS Omnibus Survey, which is available in the national data archive. Checking the data shows that the median value (i.e. half) of all working age (less than 65) population is 100. That is at least half of the working age population score 100 according to the study they quote. In fact only 8% of the working age population without long term health issues fall below a score of 85.
Hence there is a question of the validity of the changed thresholds with their mistake being made by failing to take account of the underlying data distribution.
Given this do Profs White, Sharpe and Chadler stick by their revised threshold.
3) Which other trials can they site that have a similar wide scale protocol changes. In developing a statistical plan it may be normal to look at the data distributions to choose the appropriate statistical techniques but I believe that changing outcome measures is less usual and with drug trials would require the approval of the ethics committee that approved the trial.
I would appreciate it if you could get them to answer these questions.
I have some specific questions for them could you put the questions to them or are they only making statements.
1) What mechanism did they use to control for different expectations within the different trial arms. I've read papers saying that
From Walter R. Boot, Daniel J. Simons, Cary Stothart, and Cassie Stutts The Pervasive Problem With Placebos in Psychology: Why Active Control Groups Are Not Sufficient to Rule Out Placebo EffectsAlthough active control groups are superior to “no-contact” controls, only when the active control group has the same expectation of improvement as the experimental group can we attribute differential improvements to the potency of the treatment.
Perspectives on Psychological Science July 2013 8: 445-454, doi:10.1177/1745691613491271
Yet the APT and SMC group to me seem to be setting up different expectations to the CBT and GET group. This is potentially a serious problem due to the reliance on subjective outcome measures. I believe Wechsler's asthma study showed the dangers of relying on subjective measures where they showed a placebo effect with the subjective measures but not objective ones,
Hence the question how do you know that its not just different levels of placebo effect based on different expectations being measured.
2) In their recovery paper they justify changing the threshold on the short form 36 physical function scale from 85 to 60 with the claim that half the working age population scores under 85. They quote a paper by bowling which is based on the 1992 OPCS Omnibus Survey, which is available in the national data archive. Checking the data shows that the median value (i.e. half) of all working age (less than 65) population is 100. That is at least half of the working age population score 100 according to the study they quote. In fact only 8% of the working age population without long term health issues fall below a score of 85.
Hence there is a question of the validity of the changed thresholds with their mistake being made by failing to take account of the underlying data distribution.
Given this do Profs White, Sharpe and Chadler stick by their revised threshold.
3) Which other trials can they site that have a similar wide scale protocol changes. In developing a statistical plan it may be normal to look at the data distributions to choose the appropriate statistical techniques but I believe that changing outcome measures is less usual and with drug trials would require the approval of the ethics committee that approved the trial.
I would appreciate it if you could get them to answer these questions.