Scientific Evidence Over-Rides the False Claims
in Canadian Stroke Case

This section is compiled by Frank M. Painter, D.C.
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FROM:   International Chiropractic Pediatric Association ~ I.C.P.A.

Joel Alcantara, D.C.,
Director of Research for the ICPA

The Lana Lewis inquest in Canada is well known to Canadian chiropractors as it has and will affect the practice of chiropractic in that country and possibly the world. The following is a summary from one of the expert witnesses called by the chiropractic profession, Dr. David Sackett. To some, the name may be familiar, particularly since its synonymous with the words "evidenced-based medicine."

To recap Dr. Sackett's credentials, they are the following. He is a world-renowned professor and expert in epidemiology and applied human research. Holding a Master's degree and Medical degree, he is professor emiritus at McMaster's University in Canada and was the founding chair in Epidemiology at Oxford University, England. In addition to the many accolades he has received worldwide and tons of publications, he is the founder of the journal, Evidenced-Based Medicine.

In order to aid the jury on the conflicting evidence of causation; Mr. Danson, counsel for the chiropractic profession, asked Dr. Sackett to review the principles of epidemiology as they pertain to causation. Dr. Sackett explained that when two events have a causal link (i.e., adjustments "linked" to stroke), one of four principles must be applied:

1. The first event is a cause of the second.
2. Conversely, the second event is in fact the cause of the first.
3. Alternatively, there is a third factor.
4. The cause is coincidental and unrelated to either events.

As they apply to the Lewis Inquest, Dr. Sackett testified that principle one above would ask if chiropractic manipulation would have caused an arterial dissection leading to Ms. Lewis' stroke. Principle two would ask that if Ms. Lewis had indeed had a pre-existing dissection, would this cause her to experience neck pain and thus seek the care of a chiropractor. With the third principle, one could posit that a genetic pre-condition exists that caused Ms. Lewis' dissection and caused her pain and seek the care of a chiropractor. The fourth principle posits that the events occurring to Ms. Lewis was due to chance. A great number of adjustments are performed each year in Canada (and in the rest of the world) and since arterial dissection does occur in the general population, the two events may occur coincidentally.

When asked to review how scientists study cause and effect. Dr. Sackett described four research designs and their effectiveness in leading to cause and effect. They are the following:

Level I: Randomized Clinical Trials   The effectiveness for these types of study (RCTs) have the highest rating. To date, no RCTs involving neck manipulations have been performed. Dr. Sackett noted however, that his own literature review of the Cochrane Database found 218 clinical trials involving chiropractic care. According to Dr. Sackett, this compared more favorably when held against trials done involving other professions such osteopathy, podiatry and physiotherapy, as limited to only spinal or joint research.

Level II. A Prospective Cohort Study   Two of this type of study have performed but they were small in size and have indeterminate conclusions.

Level III. A Case-Controlled Retrospective Study   One study was examined and referred to as the Rothwell study. As for this type of study in its ability to draw upon causation; it cannot be relied upon.

Level IV. A Case Series   This type of study cannot aid in drawing conclusions of cause and effect. Of interest is Dr. Sackett's comments about Dr. Norris' SPONTADS study. Dr. Sackett commented that the SPONTADS study is a Level IV research and is not relevant to the case at hand. Dr. Sackett goes on to say that Dr. Norris is not an expert in determining causation and is incompetent as a scientist in the study of causation.

Level V. Expert opinion   On the topic of risk and risk ratios. According to Dr. Sackett, there is a 200-fold difference in the spread of opinion on the true of risk of neck adjustment and their likelihood to cause stroke. Based on this, two conclusions can be put forward. One, we do not know the true risk. Two, a large study would be required to ascertain the true risk. Such a study (a Level II study) would bring to light if there is increased risk through exposure and provide a figure on the actual risk. If indeed the risk of stroke following spinal manipulation is 1 in 77,000 patients, one would require 1 million participants in the study. If the risk is 1 in 1 million, then a sample size of 12 million subjects would be required. Dr. Sackett indicated that such a study may not ne humanly possible to perform.

When asked by the chiropractic counsel if a drug caused stroke in 1 in 77,000 patients, would it be banned. Dr. Sackett testified that if that were the case, they would have to close down hospitals. He further reminded the court that drugs such as penicillin, Aspirin and anticoagulants are responsible for deaths far higher but their benefit outweighs their risk. Similarly, Dr. Sackett cited the use of NSAIDS as causing 16,500 deaths per year in the US alone but again, their benefit outweighs the risk. Dr. Sackett further commented that in a study he conducted at Oxford University; of the drugs commonly used by his clinicians, 47% had never been validated in RCTs.

Asked if the neck manipulation may have had anything to do with Ms. Lewis' stroke; Dr. Sackett believed that there is a 25% or less probability that this was the case. On the probability of Ms. Lewis' atherosclerosis, hypertension and smoking habit leading her to a stroke; Dr. Sackett's opinion of death due to natural causes was at 75% or greater probability.

On a final note, counsel for the chiropractic profession asked Dr. Sackett why he was testifying as a witness for the chiropractic profession and Dr. Sackett's reply was that he wan on "neither" side. He is a man of science and that he was there for and on behalf of science unbiased by some pre-set struggle or pre-determined belief. In Nov 2002 Dr. Adrian Upton, Head of the Department of Neurology at McMaster Health Sciences Centre testified at the inquest into the death of Lana Lewis that, based on all of the evidence he has reviewed, Ms. Lewis died of a stroke caused by advanced atherosclerosis.

During examination, he stated that a chiropractic neck adjustment she received not long before her stroke was at best "a remote possibility at the bottom of the list of probabilities" for causation.

In his testimony, Dr. Upton described the advanced nature of her atherosclerosis as a "ticking time bomb" that "could have caused her to have a stroke at any time." Dr. Upton cited Ms. Lewis' numerous risk factors for stroke including smoking, hypertension, high blood cholesterol and a family history of vascular disease. He also noted that her autopsy showed extensive intra-cranial blockage of both her left and right vertebral arteries and stated that the advanced stage of the disease was unusual for someone of her age.

"I believe the facts are pretty straightforward here," he stated and further noted that determining the cause of Ms. Lewis' stroke should not be "... an intellectual game. It should be based strictly on the facts."

When questioned about Dr. John Norris' opinion that Ms. Lewis' stroke was caused by her neck adjustment and his claims regarding the incidence of stroke related to neck adjustment, Dr. Upton stated, "I am at a loss to explain how he came to these conclusions based on the facts."

"If a theory doesn't fit the facts, we change the theory," said Dr. Upton explaining how reliable science is conducted. "In scientific debate, you stick to the facts. That is not what is happening here," he stated referring to the variety of speculation and opinion linking Ms. Lewis' stroke to neck adjustment.

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