Last month the Journal of the Royal Society of Medicine published the following article by Ernst & Cantor [click on the link for free full text]:
A systematic review of systematic reviews of spinal manipulation. E Ernst and P H Canter. J R Soc Med 2006;99 192-196. Blog entry
The June issue of the journal includes a number of letters in response to this article:Systematic review of spinal manipulation: A balanced review of evidence? Alan Breen, Steven Vogel, Tamar Pincus, Nadine Foster, Martin Underwood The Musculoskeletal Process of Care Collaboration. J R Soc Med 2006;99 277.
Systematic review of spinal manipulation: Flaws in the review. David Byfield and Peter McCarthy. J R Soc Med 2006;99 277-278.
Systematic review of spinal manipulation: A biased report. B J Lewis and G Carruthers. J R Soc Med 2006;99 278.
Systematic review of spinal manipulation: Including different techniques. Ann Moore The members of the National Council for Osteopathic Research. J R Soc Med 2006;99 278-279.Systematic review of spinal manipulation: Authors' reply. E Ernst and P Canter. J R Soc Med 2006;99 279-280.
Excerpt: We are, of course, flattered by this amount of interest in our article and would like to respond as follows to the multitude of interesting arguments. Spinal manipulation was first described in 1895 by the `magnetic healer' D D Palmer as a treatment of `subluxations' of the spine and other joints. Early chiropractors believed that `subluxations' were the cause of all diseases—to quote Palmer: `95% of all diseases are caused by displaced vertebrae, the remainder by luxations of other joints'. Today, 89.8% of (USA) chiropractors feel that spinal manipulation should not be limited to musculoskeletal conditions. It is thus not `methodologically unsound', as D Byfield and P McCarthy assume, but necessary to conduct a health technology assessment of spinal manipulations for the full range of conditions for which adequate data are available. Similarly, global assessments exist also in the chiropractic literature and are acclaimed by chiropractors—as long as they are not truly critical of their practice.
Of course, Byfield and McCarthy are right, the majority of chiropractic patients suffer from musculoskeletal problems, but are they suggesting one must not ask questions about the rest? And, of course, the `straight' chiropractors adhering to Palmer's gospel are in the minority; but, in the UK, the influence of those `vitalists', who insist spinal manipulation is a panacea, is growing.
It is not correct that we have `aggregated' different conditions. In fact, we assessed systematic reviews pertaining to different conditions quite separately. A systematic review is an accepted method for minimizing bias, the argument that our article maximized bias seems therefore illogical and has no basis. In this context it is worth noting that most of the commentators are affiliated with chiropractic or osteopathic organizations, while neither of us is on the payroll of an interested party. Byfield and McCarthy's claim that our approach `lacks statistical validity' is embarrassing—we did not use any statistics in this paper.