BMJ  2006;332:1463-1464 (24 June), doi:10.1136/bmj.332.7556.1463

Editorial

The diagnosis and treatment of carpal tunnel syndrome

Surgery—whether open or closed—works, but only if the diagnosis is right

The randomised controlled trial of Atroshi and colleagues (p 1473) in this week's BMJ shows that there are no substantive differences in the outcome of carpal tunnel syndrome treated with either a conventional open decompression of the median nerve or an endoscopic approach.¹ Their findings confirm those of earlier studies which also found no fundamental difference in outcome that could be attributed to the technique of surgical release of the carpal tunnel.^2-4

Given that the result of surgical treatment for carpal tunnel syndrome is not universally successful, however, what other factors might have an important impact on the outcome? One key determinant is probably the accuracy of the diagnosis.^{5 6} When the diagnosis is wrong treatment will fail no matter what it comprises while, as Atroshi and colleagues have shown, an accurate diagnosis is associated with success after adequate decompression by any means.

Standardised diagnostic criteria are lacking for many, if not most, medical conditions. The term "gold standard" is often used to imply that there is a definitive diagnostic criterion for a given condition, but gold standards exist only by consensus. Despite the fundamental role played by diagnosis in determining treatment and prognosis, little attention has been paid to the effect variations in diagnostic criteria may have on treatment outcomes.

Indeed, much evidence on treatment outcomes is flawed because diagnostic criteria are rarely explicitly described in intervention studies. Inconsistencies in diagnostic practices for common medical conditions may lead to differing patterns of resource use, including the use of diagnostic tests and variations in estimates of disease prevalence, treatment, and outcomes.⁷

Carpal tunnel syndrome is commonly diagnosed by a broad range of medical and surgical specialists as well as by primary care doctors working in a wide variety of practice settings. The best diagnostic criteria for the syndrome have not been established, and there is considerable disagreement as to the relative importance of various clinical findings.⁸ To a certain extent, the absence of consensus on the best diagnostic criteria for the syndrome is related to a general reliance on the results of electrodiagnostic testing as a diagnostic gold standard.

Unfortunately, the electrophysiological criteria for making a diagnosis of carpal tunnel syndrome may vary substantially between laboratories. In addition, like all laboratory tests, electrodiagnostic tests may yield both false positives and negatives. The results of electrodiagnostic tests are best interpreted in the context of clinical findings. Electrophysiological data alone cannot be taken as reliable evidence of the diagnosis of carpal tunnel syndrome, although they may be helpful in cases where there is uncertainty after a careful clinical evaluation. Under these circumstances the outcome of electrodiagnostic testing should be seen as raising or lowering the probability of the syndrome first established on clinical grounds.

The problems surrounding the evaluation and treatment of carpal tunnel syndrome, including the impact on outcomes such as workers' compensation, is a good example of the challenges facing clinical researchers in a variety of subjects. Until there is consensus on the diagnostic criteria for the disease in question, there will always be a risk of comparing apples with oranges.

For carpal tunnel syndrome, these diagnostic variations have been at least partially responsible for wide variations in the observed prevalence of the condition in different workplace settings. This has led to possibly erroneous conclusions regarding the aetiological role of certain types of work in the development of the condition, with enormous implications for insurers, patients, and employers. There are well established strategies for developing and measuring this type of consensus, such as the Delphi technique.⁹ While this approach to standardising diagnostic criteria for common medical conditions may prove to be arduous, the benefits are clear and potentially far reaching.

Toronto Western Hospital, 399 Bathurst Street, Toronto, Ontario M5T 2S8, Canada
(Brent.Graham{at}uhn.on.ca)

---

Competing interests: None declared.

Research p 1473

References

1. Atroshi I, Larsson G-U, Ornstein E, Hofer M, Johnsson R, Ranstam J. Outcomes of endoscopic surgery compared with open surgery for carpal tunnel syndrome among employed patients: randomised controlled trial. BMJ 2006;332: 1473-6.[Abstract/Free Full Text]
2. Brown RA, Gelberman RH, Seiler JG 3rd, Abrahamsson SO, Weiland AJ, Urbaniak JR, et al. Carpal tunnel release. A prospective, randomized assessment of open and endoscopic methods. J Bone Joint Surg Am 1993;75: 1265-75.[Abstract/Free Full Text]
3. Macdermid JC, Richards RS, Roth JH, Ross DC, King GJ. Endoscopic versus open carpal tunnel release: a randomized trial. J Hand Surg [Am] 2003;28: 475-80.[CrossRef][Medline]
4. Saw NL, Jones S, Shepstone L, Meyer M, Chapman PG, Logan AM. Early outcome and cost-effectiveness of endoscopic versus open carpal tunnel release: a randomized prospective trial. J Hand Surg [Br] 2003;28: 444-9.[CrossRef][Medline]
5. Hunt TR, Osterman AL. Complications of the treatment of carpal tunnel syndrome. Hand Clin 1994;10: 63-71.[ISI][Medline]
6. Kessler FB. Complications of the management of carpal tunnel syndrome. Hand Clin 1986;2: 401-6.[ISI][Medline]
7. Crombie DL, Cross KW, Fleming DM. The problem of diagnostic variability in general practice. J Epidemiol Community Health 1992;46: 447-54.[Abstract/Free Full Text]
8. Graham B, Dvali L, Regehr G, Wright JG. Variations in diagnostic criteria for carpal tunnel syndrome among Ontario specialists. Am J Ind Med 2006;49: 8-13.[CrossRef][ISI][Medline]
9. Graham B, Regehr G, Wright JG. Delphi as a method to establish consensus for diagnostic criteria. J Clin Epidemiol 2003;56: 1150-6.[CrossRef][ISI][Medline]

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Relevant Articles

A good read

Fiona Godlee
BMJ 2006 332: 0. [Extract] [Full Text] [PDF]

Outcomes of endoscopic surgery compared with open surgery for carpal tunnel syndrome among employed patients: randomised controlled trial

Isam Atroshi, Gert-Uno Larsson, Ewald Ornstein, Manfred Hofer, Ragnar Johnsson, and Jonas Ranstam
BMJ 2006 332: 1473. [Abstract] [Full Text] [PDF]

Rapid Responses:

Read all Rapid Responses

The incision shown on the front cover

Ilana Langdon
bmj.com, 25 Jun 2006 [Full text]