Ian McWilliam’s comments on the Dunedin Chelation Study [Forum, September] indicates the many difficulties in understanding medical research papers. In consideration of his critique of the study:
Re the number of patients:
- Whilst 32 is not many, they were all typical claudication sufferers, being mainly smokers, male, and average age 67.
- Van Rij et al arrived at this number in the correct method: using “power” and type error and allowing for detecting a predicted significant improvement in the order of 10% in terms of walking distance. Thus the study would easily detect the sorts of improvement that would be clinically significant (ie the 50-100% touted by some chelation clinics).
Re Mr McWilliam’s doctor friend’s analysis:
- His statement that only 12% of the controls achieved 100% walking distance improvement versus 26% for the chelation group is poor presentation of statistics: We don’t know how many of the controls achieved 99% or similar walking distance improvement.
Van Rij et al quote a change in the average walking distance to pain (ie how long before the patients stopped walking because of pain) in the order of 25 metres improvement for the controls verses only 12 metres for the chelation patients. In other words the chelation group did worse. An average is a better statistic in this case than the ones quoted by Mr McWilliam.
Mr McWilliam’s statistical analysis (95% confidence limits) is irrelevant given no explanation of the statistical method used and who performed the test.
Comments that “Those who supply the expensive drugs, equipment and surgery would lose much if research into other simpler, less expensive…” ignores the extensive research by the “heart industry” into the likes of aspirin and warfarin, hardly expensive medications.
I have found the results of the Dunedin Chelation Study significant for my clinical practice: It has reaffirmed my clinical observation of several patients who have undergone chelation; they all feel significantly better for the extensive attention they receive and the improvements they achieve in their lifestyle — i.e. enhanced placebo effect. Unfortunately the cost of this “placebo” is excessive, its long-term effects questionable and I have a degree of unease when I consider the number of chelation-treated patients I have had die from their heart and circulation disease within two years following therapy.
Jim Vause, Blenheim