Rheumatology 2001; 40: 595-597
© 2001 British Society for Rheumatology
Letters to the Editor |
Diagnosis of carpal tunnel syndrome
Wythenshawe Hospital, Southmoor Road, Manchester M23 9LT, UK
SIR, I read with interest the paper by O'Gradaigh and Merry on the use of Bayes's theorem to produce a diagnostic algorithm for carpal tunnel syndrome [1]. Bayes's theorem may have a useful place in clinical practice, as also indicated by our own previous study [2] with regard to isotope scanning of sacroiliac joints in suspected inflammatory spondylitis as well as with HLA-B27 typing of these patients.
As pointed out by the authors, our own recent study did reveal long waiting times for the simple nerve conduction tests that are so useful in evaluating patients with paraesthesia, including suspected carpal tunnel syndrome [3]. I would, however, like to voice some concerns on diagnosing the majority of patients using the suggested algorithm and without the use of nerve conduction tests, as advocated by the authors for a number of reasons.
First, I would like to question the use of a single criterion for diagnosing carpal tunnel syndrome in this study (the definitive test being sensory amplitude <10 mV or motor latency >3.7 ms). In my opinion a better validated study is necessary (before advocating less use of nerve conduction tests) with more stringent criteria for carpal tunnel syndrome that are generally acceptable not only for scientific studies but also in routine practice. The authors do not indicate which nerves they tested to indicate the sensory amplitude and motor latency, but one would presume that they mean the median nerves. For more diagnostic accuracy for carpal tunnel syndrome other criteria need to be included, such as median nerve sensory velocity, median nerve motor latency compared with the ulnar nerve motor latency in the same hand, and indeed compared with the other hand (especially if asymptomatic). In most centres, to the best of my knowledge, median nerve motor latency >3.7 ms may still be normal, as on average the accepted maximum normal value for this test is 4.0 ms [4], but even this is arbitrary as people's hand sizes vary. One can easily appreciate the magnitude of the possibility of false-positive tests, as many patients who may be symptomatic in the hands for various other conditions, for example cervical disc disease, may well have median nerve motor latencies falling between 3.7 and 4.0 ms, in which case a false-positive diagnosis of carpal tunnel syndrome would have been made by the single criterion used by the authors.
Furthermore, I would like to point out that even an obviously positive Phalen's test, with or without the presence of Tinel's sign (which in my experience has been quite a useless test because of many false positives), can be demonstrated in many patients whose nerve conduction tests have proved absolutely normal. Such patients may include those with cervical disc disease, cervical myelopathy, anxiety and depression, and non-specific complaints in patients with conditions such as fibromyalgia or in early peripheral neuropathy. One further query that I have with the authors is with regard to the time taken to designate a positive Phalen's test (1 min); the standard description of the test suggests reproduction of symptoms within 20 s. It has been my experience that some patients do not understand the significance of the reproduction of symptoms; in particular, patients who do not actually have median nerve compression may inappropriately respond positively, indicating a positive test when they do not experience the type of symptoms experienced by actual carpal tunnel syndrome patients. Hence confusion often arises in clinical practice, especially in busy clinics.
The above comments are based on my long experience in dealing with this group of patients and basic nerve conduction tests. In addition, my colleagues and I have performed [3–5] and are currently undertaking a number of studies which raise concerns about the type of conclusion O'Gradaigh and Merry have drawn from their study. For example, in patients with paraesthesia (but normal neurophysiological tests) in the hands (with or without positive Phalen's and/or Tinel's test), when assessed by the Hospital Anxiety and Depression scale, a significant proportion show high scores (paper in preparation).
I agree with the authors, however, that in milder and early cases of carpal tunnel syndrome (with three positive clinical tests as they described), apart from splinting of the hand and wrist, a steroid injection may be appropriate whilst waiting for electrophysiological tests; in my experience about half the patients do respond. Such patients do not require decompression surgery straight away, as often advocated, particularly by orthopaedic and plastic surgeons. Finally, I would like to draw your readers’ attention to the proposed guidelines for carpal tunnel syndrome management that we have published in the paper quoted by the authors [3].
Accepted 27 November 2000
References
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O'Gradaigh D, Merry P. A diagnostic algorithm for carpal tunnel syndrome based on Bayes's theorem. Rheumatology2000; 39:1040–1.
[Abstract/Free Full Text] -
Diffey BL, Pal B et al. Application of Bayes' theorem in the diagnosis of ankylosing spondylitis using isotope scanning of the sacro-iliac joint. Ann Rheum Dis1985;44:667–70.
[Abstract/Free Full Text] -
Pal B, Morris J, Kelman J, Mangion P. A survey of approaches to diagnosis and management of idiopathic carpal tunnel syndrome by rheumatologists and proposed guidelines. Br J Rheumatol1997;36:1328–30.
[Abstract/Free Full Text] - Pal B, Mangion P, Hossain MA et al. A controlled trial of diuretics in idiopathic carpal tunnel syndrome. Clin Rehab1988;2:49–51.
- Pal B, Keenan J, Misra HN et al. Raynaud's phenomenon in idiopathic carpal tunnel syndrome. Scand J Rheumatol1996; 25:143–5.[Medline]
Reply
Department of Rheumatology, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK
SIR, We have read Dr Pal's comments, which highlight the polarization of the debate in this area. His views are widely published and acknowledged by us. We are grateful for the opportunity to answer his concerns.
Nerve conduction studies (NCS) followed the practice at that time in the Department of Neurology where one of us (DO'G) was trained to carry out these tests, and closely followed accepted methods [1]. Within the constraints of a concise report, we did not detail the NCS procedure. We can confirm that the detailed study recommended by Dr Pal, comparing with the ipsilateral ulnar nerve and comparing both hands, was indeed carried out. Normal ranges were derived from the instrument manufacturer's data. Reviewing the data from our cohort, 23 patients (of 137 records available) had a distal motor latency between 3.7 and 4.0 ms. In published studies (including that by Goldring et al. [2] to which Dr Pal et al. referred in their paper advocating NCS [10]), a single criterion is used, usually including a comparison with the ulnar nerve, as in our study. Sensory neurones are often first affected alone, and a single criterion based on tests of the sensory component of the median nerve will detect carpal tunnel syndrome (CTS) at an earlier stage.
Dr Pal refers to his personal experience of Tinel's and Phalen's tests. Numerous objective publications [e.g. 3, 4] report sensitivities and specificities in the range of 60–80% for these tests. While insufficient alone, we contend that the tests are not ‘useless’, but are positively useful when combined in the novel way we have proposed and supported with our data. The interpretation of a positive Phalen's or Tinel's test does indeed include many of the differentials suggested by Dr Pal. While we believe that our algorithm obviates the need for NCS in selected cases, we did indicate that patients were first selected on the basis of clinical judgement, which no test (including NCS) can replace. Furthermore, positive provocative tests may occur in the face of normal NCS in the setting of ‘dynamic’ CTS ([5] and discussed in more detail in our intervention study [6]).
Dr Pal's final comments relate to Phalen's test (first described by Phalen as a wrist flexion test, for 60 s [7]). We reviewed the literature before conducting this study, and found that the description of Phalen's test encountered on each occasion [3, 4 and others referred to therein] describes an interval of 60 s (occasionally 30–60 s), and we are not aware of an alternative ‘standard description’ as mentioned by Dr Pal (without reference). An interesting study [8] (published after the commencement of our study and therefore not considered in its design) used a receiver–operator curve to determine the optimal duration of Phalen's test. Forty seconds gave the best overall sensitivity and specificity, although sensitivity was greater at 60 s, while 20 s was markedly less sensitive with relatively little gain in specificity. Dr Pal also suggests that busy clinicians are confused in interpreting this test, but in our study, carried out in a dedicated research clinic, the test was carefully evaluated in each patient.
Finally, we look forward to reading Dr Pal's paper regarding scores on the Hospital Anxiety and Depression scale in patients with normal NCS. Given the considerable symptoms, nocturnal wakening and loss of hand function experienced by CTS suffers, these HAD scores might be interpreted in different ways. We would hope that clinical acumen does indeed prevail and that the false negative rate of NCS [9] is also considered when evaluating these patients.
In conclusion, we would reiterate Dr Pal's interpretation of our study that patients with three positive tests can be offered corticosteroid injection [3] without resort to NCS. However, the value of referral of these patients for NCS, which might be performed perhaps 12 weeks later, is debatable, unless symptoms fail to resolve or subsequently relapse.
Notes
Correspondence to: D. O'Gradaigh. 
References
- Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH. Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle Nerve1993;16:1392–414.[Web of Science][Medline]
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Goldring DN, Rose DM, Selvarajah K. Clinical tests for carpal tunnel syndrome: an evaluation. Br J Rheumatol1986;25:388–90.
[Abstract/Free Full Text] -
Gellman H, Gelberman RH, Tan AM, Botte J. Carpal tunnel syndrome: an evaluation of the provocative tests. J Bone Joint Surg1986;68A:735–7.
[Abstract/Free Full Text] - Seror P. Phalen's test in the diagnosis of carpal tunnel syndrome. J Hand Surg1988;13B:383–5.[Medline]
- Braun M, Davidson K, Doehr S. Provocative testing in the diagnosis of dynamic carpal tunnel syndrome. J Hand Surg1989; 14A:195–8.
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O'Gradaigh D, Merry P. Corticosteroid injection in the treatment of carpal tunnel syndrome. Ann Rheum Dis2000;59:918–9.
[Abstract/Free Full Text] -
Phalen GS. Carpal tunnel syndrome. 17 years experience in diagnosis and treatment of 654 hands. J Bone Joint Surg1966; 48A:211–28.
[Abstract/Free Full Text] - Tetro AM, Evanoff BA, Hollstein JB, Gelberman RH. A new provocative test for carpal tunnel syndrome. Assessment of wrist flexion and nerve compression. J Bone Joint Surg1998;80B:493–8.
- Grundberg AB. Carpal tunnel decompression in spite of normal electromyography. J Hand Surg Am1983;8:348–9.[Medline]
- Pal B, Morris J, Keenan J, Mangion P. Management of idiopathic carpal tunnel syndrome (ICTS): a survey of rheumatologists' practice and proposed guidelines. Br J Rheumatol1997; 36:1328–30.
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