TU QUOQUE (You did it too)
By John Reggars DC, MChiroSc.

The above Latin phrase has often been used as a line of reasoning by alternative and complimentary medicine disciples in defending their treatment or diagnosis against criticism from the medical profession. That is, one party cannot criticise another because both parties are guilty of the same sin. In particular, this argument has been used by numerous chiropractic authors, in the context that only 10 to 20% or less of standard Western medicine is evidence based, and therefore by implication, if true, it might justify a variety of unproven treatments with a similar dearth of supporting evidence.

So what is the origin of the quotation that “only 10 - 20% or less of standard Western medicine is evidence based”? Well, it appears that even this quotation is not at all evidence based and like many urban myths has been accepted as fact, simply through repetition within the literature. Analogous to this myth was the well accepted, yet unjustified, assertion that 90% of patients with acute low back pain will recover within four weeks. This conclusion, by Dillane et al¹, was based on their study in general practice where one of their outcome measures was that if the patient did not return to their practice for follow-up they were assumed to have recovered. The recommendation that the average person requires eight glasses of water per day is another classic example of how, from an unsupported statement, a particular recommendation or view point becomes accepted as fact simply through repeated reference to the original statement.²

Imrie and Ramey sought to identify the origins of statement that only 10 to 20% or less of standard Western medicine is evidence-based.³ According to the authors the original claim first appeared in print in a document published by the U.S. Congressional Office of Technology Assessment (OTA) in 1979 and was repeated in 1983. The statement is attributed to a noted epidemiologist, Dr. Kerr White. Apparently Dr. White based his informal 10 – 20% estimate on a 1963 paper that reported on two surveys, conducted over two weeks, on the prescribing practices of 19 family doctors in a northern British town. One survey was conducted in December 1960 and another in March 1961. According to Imrie and Ramey, the paper was never intended to evaluate the science of medical practice, rather its purpose was to look toward controlling prescribing costs in terms of generic versus proprietary drugs. The intent of each prescription was analysed according to how specific it was for the condition. Intent was specific for the condition for which it was prescribed only in about 10% of the time. Dr. White himself noted that his assessments were never intended to be applied generally.

Nevertheless, in 1995 Dr. White stated, “Some 20 years ago, as a member of the original Health Advisory Panel to the US Congressional Office of Technology Assessment I ventured the 10 – 20% figure again and invited anyone to provide me with more timely data. No one could. The figure was immortalised in OTA circles and publications for almost a decade. In countless addresses and conferences I often challenged others to provide better evidence but none was forthcoming. So the northern industrial town ‘armchair” assessment persisted.”

Then in 1991, at a conference in Manchester UK, Dr David Eddy, claimed that only 15% of medical practice was based on any evidence at all. He apparently based his assertion on his studies of just two specific conditions: arterial blockage in the legs and glaucoma. Like Dr White’s “armchair” assessment Dr Eddy’s unsubstantiated claim was widely cited as a criticism of mainstream medicine.

Although when these claims were made no solid evidence existed to either refute or support them, a growing body of evidence now exists regarding the extent to which medical practice is evidence-based. The question then arises as to what constitutes acceptable evidence. Imrie and Ramey suggest that on average 37.02% of interventions are supported by randomised controlled trials (RCT) and that 76% of interventions are supported by some form of compelling evidence. The authors also note that many interventions have not been tested via RCT because they are termed “self-evident” interventions such as blood transfusions antibiotics for meningitis, a tourniquet for a bleeding wound etc. and to test some interventions via RCT would be unethical.

Imrie and Ramey quite rightly note that evidence-based practice has its critics. Some for instance assert that this philosophy of practice has major limitations when considering the care of individual patients and that anecdote, testimony and clinical (personal) experience should be afforded equal weight to ostensibly more objective scientific evidence. Now doesn’t that sound familiar? With respect to Dr White’s claim in the OTA report, the authors state, “Clearly the intent of the OTA report was to strengthen the scientific basis for medical care, not to promote an “open door policy for unproven alternative and complimentary therapies.”

Nonetheless, I am sure that the baseless claim that only 10 – 20% of medical interventions are evidence-based, will be perpetuated by the dogmatic “fundamentalists” within the chiropractic profession who will continue to cry “tu quoque” in their defence of their unproven treatments.

1. Dillane JB, Fry J, Kalton G. Acute low back syndrome – A study form general practice. 1966 BMJ 2: 82-4.
2. Reggars J. Eight glasses of water per day. COCA News June 2004.
3. Imrie R, Ramey DW. The evidence for evidence-based medicine. 2000 Compl Ther in Med 8: 123-6.