Re: Centralization phenomenon

Issue: BCMJ, vol. 46, No. 9, November 2004, Pages 439-440 Letters

We would like to thank the BC Medical Journal for the opportunity to respond to some of the issues raised by Dr Bishop in Counterpoint September 2004 [BCMJ 2004;46:349, 353-354].

Dr Bishop raises the important point of reliability, an essential element of every assessment system. We were remiss in not including this in our paper. Dr Bishop questions the reliability of the McKenzie assessment based on one article by Riddle et al. Why he selected this one study and omitted the four subsequent studies that demonstrate strong reliability is unclear.[1-4] It is noteworthy that these other four all used clinicians fully educated in McKenzie methods while the Riddle study used novice clinicians.

Dr Bishop describes the importance of establishing guidelines; we agree. The Danish Institute for Health Technology Assessment published in 1999[5] differs from other guideline groups in that they are the first to review the literature investigating the McKenzie assessment procedures independent from the literature on treatment. They assigned the McKenzie assessment their highest grade for scientific support for reliability and validity.

Borkan and colleagues 1998,[6] Bouter and colleagues 1998,[7] and Bouter and colleagues 2003 of the Cochrane Back Review Group[8] all described the vital necessity of trying to identify distinct subgroups in the broad category of non-specific back pain. Randomized controlled trials are not the appropriate study design for identifying subgroups. Guidelines panels will need to look to other study designs, as Denmark did, to fulfill our fundamental need to identify and validate subgroups.

Our original article [BCMJ 2004;46:348, 350-352] on the centralization phenomenon cited numerous studies that, without exception, demonstrated that patients whose symptoms centralize form a distinct subgroup in the low back pain population based on their consistently superior outcomes compared with non-centralizers, another distinct subgroup, that typically have slow or non-recoveries. To be able to make such a distinction at the outset of care is of great value, especially if the assessment also identifies patient-specific exercise and posture strategies that centralize, abolish, and then prevent the return of the pain.

These international experts we have referenced correctly state that future randomized controlled trials should focus on treatment interventions for these subgroups, illustrated by the Long and colleagues study we cited, due to be published in Spine in December. This study dramatically demonstrates the superiority of subgroup-specific treatments with every outcome measured. It is rather like conducting a trial of nitroglycerin for patients with angina vs only studying those with non-specific chest pain. The medication is clearly demonstrated as useful and efficacious in the former study but barely better than doing nothing in the latter. Results will always be confusing, even misleading, if we continue to study non-specific low back pain, just as in the 1998 Cherkin study Dr Bishop cited, which reported a lack of efficacy of either chiropractic or McKenzie in a non-specific back pain sample.

We consider Dr Bishop’s dismissal of the value of the McKenzie assessment to be based on an incomplete knowledge of the relevant literature. In actuality, the evidence supporting the reliability and validity of a McKenzie-based examination is, as we previously stated, already strong and growing steadily.

—C.L. Davies, Vancouver
—C.M. Blackwood, MD, Mission


1. Razmjou H, Kramer JH, Yamada R. Intertester reliability of the McKenzie evaluation in assessing patients with mechanical low back pain. JOSP 2000;30:368-389. PubMed Abstract 
2. Kilpikoski S, Airaksinen O, Kankaanpa M, et al. Interexaminer reliability of low back pain assessment using the McKenzie method. Spine 2002;27:E207-E214. PubMed Abstract Full Text 
3. Fritz J, Delitto A, Vignovic M, et al. Interrelator reliability of judgments of the centralization phenomena and status change during movement testing in patients with low back pain. Arch Phys Med Rehab 2000;81:57-61. PubMed Abstract 
4. Werneke M, Hart DL, Cook D. A descriptive study of the centralization phenomenon. A prospective analysis. Spine 1999;24:676-683. PubMed Abstract Full Text 
5. Maaniche C, Gam A. Low back pain: Frequency, management and prevention from an HTA perspective. Expert panel from the Danish Institute for Health Technology Assessment. 1999. Series B:1:70. 
6. Borkan J, Koes B, Reis S, et al. A report from the second international forum for primary care research on low back pain; re-examining priorities. Spine 1998;23:1992-1996. PubMed Abstract Full Text 
7. Bouter L, van Tulder M, Koes B. Methodologic issues in low back pain research in primary care. Spine 1998;23:2014-2020. PubMed Abstract Full Text 
8. Bouter L, Pennick V, Bombardier C. Cochrane back review group. Spine 2003;28:1215-1218. PubMed Citation Full Text

. Re: Centralization phenomenon. BCMJ, Vol. 46, No. 9, November, 2004, Page(s) 439-440 - Letters.

Above is the information needed to cite this article in your paper or presentation. The International Committee of Medical Journal Editors (ICMJE) recommends the following citation style, which is the now nearly universally accepted citation style for scientific papers:
Halpern SD, Ubel PA, Caplan AL, Marion DW, Palmer AM, Schiding JK, et al. Solid-organ transplantation in HIV-infected patients. N Engl J Med. 2002;347:284-7.

About the ICMJE and citation styles

The ICMJE is small group of editors of general medical journals who first met informally in Vancouver, British Columbia, in 1978 to establish guidelines for the format of manuscripts submitted to their journals. The group became known as the Vancouver Group. Its requirements for manuscripts, including formats for bibliographic references developed by the U.S. National Library of Medicine (NLM), were first published in 1979. The Vancouver Group expanded and evolved into the International Committee of Medical Journal Editors (ICMJE), which meets annually. The ICMJE created the Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals to help authors and editors create and distribute accurate, clear, easily accessible reports of biomedical studies.

An alternate version of ICMJE style is to additionally list the month an issue number, but since most journals use continuous pagination, the shorter form provides sufficient information to locate the reference. The NLM now lists all authors.

BCMJ standard citation style is a slight modification of the ICMJE/NLM style, as follows:

  • Only the first three authors are listed, followed by "et al."
  • There is no period after the journal name.
  • Page numbers are not abbreviated.

For more information on the ICMJE Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals, visit

BCMJ Guidelines for Authors

Leave a Reply