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The Value Added by Electrodiagnostic Testing in the Diagnosis of Carpal Tunnel Syndrome
Brent Graham, MD1
1 Hand Program, Toronto Western Hospital, 399 Bathurst Street, East Wing 2-425, Toronto, ON M5T 2S8, Canada. E-mail address: Brent.Graham@uhn.on.ca
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Disclosure: In support of his research for or preparation of this work, the author received, in any one year, outside funding or grants in excess of $10,000 from the Research Advisory Council of the Workplace Safety and Insurance Board. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.
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Investigation performed at the University Health Network, Toronto Western Hospital, Toronto, Ontario, Canada

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2008 Dec 01;90(12):2587-2593. doi: 10.2106/JBJS.G.01362
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Abstract

Background: There is no clear-cut consensus on the best diagnostic criteria for carpal tunnel syndrome. The objective of this study was to compare the probability of carpal tunnel syndrome being present following electrodiagnostic testing with the probability of it being present after the diagnosis was established on the basis of a clinical evaluation alone.

Methods: The study sample included patients with any peripheral nerve diagnosis who had been referred to the electrodiagnostic laboratory of an academic health-care center. The probability of carpal tunnel syndrome before electrodiagnostic testing (pretest probability) was estimated with use of the CTS-6, a validated clinical diagnostic aid that is used to estimate the probability of carpal tunnel syndrome on the basis of the presence or absence of six clinical findings recorded as part of the history or noted on physical examination. All patients then underwent a standard electrodiagnostic assessment of the median nerve by a neurologist blinded to the result of the CTS-6 evaluation. Sensory nerve conduction velocity was used to classify the result of the electrodiagnostic testing as either positive or negative for carpal tunnel syndrome with use of two different criteria (one stringent and one lax) derived from the literature. The main outcome measure was the difference between the pretest and posttest probabilities of carpal tunnel syndrome.

Results: One hundred and forty-three patients were studied. The pretest probability of carpal tunnel syndrome ranged between 0.10 and 0.99 (mean [and standard deviation], 0.81 ± 0.22). Seventy-three percent of the patients had a pretest probability of at least 0.80. The average change in probability for these patients was -0.02 when the stringent electrodiagnostic criterion was used and -0.06 when the lax criterion was used. With either electrodiagnostic criterion, the majority of the large changes in probability were for patients for whom the pretest probability was =0.50. The probability of carpal tunnel syndrome was lowered after the electrodiagnostic testing in most of these cases.

Conclusions: For the majority of patients who are considered to have carpal tunnel syndrome on the basis of their history and physical examination alone, electrodiagnostic tests do not change the probability of diagnosing this condition to an extent that is clinically relevant.

Level of Evidence: Diagnostic Level I. See Instructions to Authors for a complete description of levels of evidence.

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    References

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    Brent Graham, MD
    Posted on March 19, 2009
    Dr. Graham responds to Mr. Kamath and Mr. Stothard
    Toronto Western Hospital

    Clearly the issue of establishing the right gold standard for carpal tunnel syndrome is a difficult one. The key consideration is that of consensus. Whatever criterion is chosen as the gold standard for the diagnosis – expert clinical evaluation, electrodiagnostic tests or response to treatment – there must be a consensus that this is an acceptable standard or that criterion will lack usefulness. It is clear that many, possible a majority, of diagnosticians do not believe that electrodiagnostic testing should be the gold standard. As the study showed in most instances, this test doesn’t add materially to the diagnostic process. Unfortunately, the response to treatment, while it is appealing as a logical correlate to diagnosis is flawed for a number of reasons. To begin with, not all those who have a diagnosis are necessarily treated so an evaluation of the value response to treatment isn’t really possible in many instances. In addition, it is clear that some patients who do not have carpal tunnel syndrome get better when they are treated for something else and conversely many instances when patients who do have carpal tunnel syndrome do not seem to improve after treatment. The causes for this can be many: inadequate release, delayed improvement due to wallerian degeneration secondary to prolonged or extreme compression, and the various effects on workers’ compensation on the apparent outcome of treatment. Because of these considerations, we have chosen the consensus of a panel of experts as the most reliable standard for the diagnosis in carpal tunnel syndrome, though admittedly perfect consensus on this idea may not exist. Nonetheless, excellent consensus was obtained among the disparate group of medical and surgical experts who contributed to the original scale.

    In our original communication describing the diagnostic scale, the weightings were described and based on the logistic regression model that was developed from the data. Figure 3 in the JBJS paper shows a point system for clinical use that is based on the regression coefficients in the model.

    Vijay Kamath
    Posted on February 26, 2009
    Value of A History Based Questionaire In The Diagnosis of Carpal Tunnel Syndrome
    James Cook University Hospital, Middlesborough, United Kingdom

    To the Editor:

    The studies by Graham (1,2) use techniques that are well established in developing consensus management for common conditions. We were especially interested to learn that for carpal tunnel syndrome, the clinical history and examination can produce the same diagnostic conclusions as nerve conduction studies.

    We looked at this problem some years ago using a rather simpler statistical model and came to the same conclusion (3).The difficulty we had noted with many previous research publications(especially those studying the sensitivity and specificity of individual tests or combination of tests e.g. Phalens and Tinel test) was that Nerve Conduction Studies were used as the so called gold Standard. To compare these tests with nerve conduction studies, we needed a new standard; the standard we adopted was improvement of symptoms after Carpal tunnel surgery. We found that history taking was much more revealing diagnostically than were the results of individual tests. This is because a Phalens test is sensitive but not specific as it is present in a fair number of people without carpal tunnel syndrome, and a Tinel test is only present in 30 to 40 percent of people with known carpal tunnel syndrome (but is specific as it is not present in people without).

    We constructed a questionnaire based on the patient's history that could be administered by primary care physicians (3). The methodology used by Dr. Graham (1) gives a full list of unweighted clinical diagnostic criteria that include only two history items, numbness and tingling in the median nerve distribution, and nocturnal numbness. In our history based questionnaire (3), we weighted these items heavily but we feel that these two questions alone are not sufficient to capture the whole relevant history.

    The test we developed has been cited in 15 publications including an information leaflet for primary care physicians developed by the Arthritis and Rheumatism Council (4). If we look at the diagnostic criteria in appendix 2 of the original article by Dr. Graham et al. (2), we see that the formula is:

    p(CTS)/1-p(CTS)=eb+b1X1+b2X2+b3X3+b4X4=b5x5+b6X6 where b0=-2.4;variable present=1, absent=0;b1=1.44;x1= thenar atrophy;b2=1.44;x2=Phalens test;b3=1.30;x3=loss of 2-point discrimination; b4=1.16;x4 =Tinel’s sign;b5=1.16;x5=nocturnal numbness;b6=1.03;x6=numbness, median nerve distribution

    The application of this formula is probably too complex for general screening. We wonder if Dr. Graham has any comments as to how it could be made more “user friendly”.

    The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

    References

    1. Graham B. The value added by electrodiagnostic testing in the diagnosis of carpal tunnel syndrome. J Bone Joint Surg Am. 2008;90:2587-93.

    2. Graham B, Regehr G, Naglie G, Wright JG. Development and validation of diagnostic criteria for carpal tunnel syndrome. J Hand Surg [Am]. 2006;31:919-24.

    3. Kamath V, Stothard J. A clinical questionnaire for the diagnosis of carpal tunnel syndrome [erratum in J Hand Surg [Br]. 2004; 29(1):95-6]. J Hand Surg [Br]. 2003;28(5):455-9.

    4. Barnardo J. Carpal Tunnel Syndrome: 2004: No 3ARC Booklet, Reports on the Rheumatic Diseases Series 5.

    Brent A. Graham, MD, MSc, FRCSC
    Posted on December 16, 2008
    Dr. Graham responds to Dr. Ring
    University of Toronto/University Health Network Hand Program, Toronto Western Hospital

    Dr. Ring brings up a few important points that are worth considering. As diagnosticians our task is to evaluate the presenting complaint of the patients and make an analysis of its most likely cause. Frequently the complaint of pain will predominate in a patient with a condition like nerve compression. Nonetheless it is well accepted that the cardinal symptom in these cases is a sensory disturbance. This dysesthesia can certainly be considered painful but the first objective of the clinician is to understand what it is that the patients are experiencing, regardless of their description. There is no diagnostic value in taking the complaint of pain at face value if it is clear that what they actually mean is painful dysesthesia. The sensory disturbance is a marker for considering a neurologic basis for the symptoms. If there is pain that is not associated with a sensory disturbance then an alternative diagnosis should be sought. This principle is reflected in the composition of the CTS-6, which as Dr Ring points out, has a strong focus on nerve dysfunction. The development of this instrument was methodologically rigorous and it’s content essentially summarizes the practices of expert clinicians from a wide spectrum of both medical and surgical specialties [1]. It has to be concluded that this is the approach with the greatest diagnostic utility.

    I would concur with Dr. Ring that were electrodiagnostic testing taken as the reference standard then a clinical evaluation would not add much to the diagnostic process. However I would submit that a careful and simple clinical evaluation using the CTS-6 criteria is certainly easier, less costly, timelier and less uncomfortable for patients so I would not agree with Dr. Ring that “an objective, neurophysiologic reference standard” is required. The reliable conduct of a clinical assessment encompassed by the CTS-6 should be well within the scope of any primary care physician and even, as the study showed, an appropriately trained allied health worker. As for the patient with “moderate to severe nerve dysfunction”, the data in the paper shows that the changes in the probability of carpal tunnel syndrome resulting from electrodiagnostic testing are particularly small in these patients.

    Finally, with respect to the extent of symptoms that bring a patient to the physician, it seems unlikely that any kind of generalization is possible. It is true however that whatever kind of treatment is recommended it must be based on a diagnosis that is reliably established, preferably with the least expense and discomfort. For most cases of carpal tunnel syndrome it appears that this should not require the use of electrodiagnostic testing.

    Reference

    1. Graham, B., et al., Development and validation of diagnostic criteria for carpal tunnel syndrome. J Hand Surg [Am], 2006. 31(6): p. 919 -24.

    Venkat R. Mekala
    Posted on December 04, 2008
    Autonomic Dysfunction in Carpal Tunnel Syndrome
    Mayday University Hospital, Croydon

    To the Editor:

    We read the article by Dr Graham (1) with great interest. The article reinforces the widely-held concept that Carpal Tunnel Syndrome (CTS) is a clinical diagnosis and that electrodiagnostic studies seldom add to clincal decision making.

    With this in mind, readers of The Journal should be aware that all three components of the peripheral nerve are potentially affected by compression neuropathy and that autonomic dysfuction in CTS is often overlooked.

    A recent prospective study confirmed that the autonomic deficit is CTS is real and quantifiable and can be used as an adjunct to diagnosis (2).

    The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

    References

    1. Brent Graham The Value Added by Electrodiagnostic Testing in the Diagnosis of Carpal Tunnel Syndrome J Bone Joint Surg Am 2008; 90: 2587-2593.

    2. Kumar A, Bismil Q, Morgan B, Ashbrooke A, Davies S, Solan M. The "biro test" for autonomic dysfunction in carpal tunnel syndrome. J Hand Surg Eur Vol. 2008 Jun;33(3):355-7.

    David Ring, MD
    Posted on December 02, 2008
    Is carpal tunnel still a syndrome?
    Massachusetts General Hospital

    To the Editor:

    In his recent article(1), Dr. Graham found that electrophysiological testing did not appreciably alter the odds of having carpal tunnel syndrome that were based on clinical criteria alone. It should be acknowledged that his criteria (the CTS-6) focus on nerve dysfunction (numbness, atrophy, weakness, and abnormal provocative tests) whereas other diagnostic/severity criteria (e.g. those of Levine and colleagues (2)) give strong weight to pain complaints. I think it is correct of Dr. Graham to conclude that electrodiagnostic testing does not add much when symptoms and signs characteristic of median nerve dysfunction at the carpal tunnel are present, but there are more practical and meaningful ways to interpret his data and analysis.

    Consider the converse of his conclusion, which while not specifically evaluated is very likely to be true: in the presence of abnormal electrophysiological testing of the median nerve at the carpal tunnel, clinical criteria do not appreciably affect the odds of carpal tunnel syndrome at the wrist. The differences between the lax and stringent criteria for diagnosing carpal tunnel syndrome on the basis of electrophysiological testing are probably not clinically relevant because these thresholds represent--at worst--very mild median nerve dysfunction at the carpal tunnel. Such mild median nerve dysfunction does not seem to bring most of us to the doctor and, if we do go, a night splint is usually satisfactory initial treatment. As such, we should be most interested in the moderate to severe median nerve dysfunction that would satisfy any electrophysiological threshold. This line of thinking supports an objective, neurophysiological reference standard for this diagnosis.

    Either way you argue it, Dr. Graham’s work adds to the growing evidence that carpal tunnel syndrome is no longer a syndrome (a collection of symptoms and signs). Just as consumption became tuberculosis, it seems appropriate to diagnose and treat the discrete, objective, verifiable disease of median nerve dysfunction at the carpal tunnel rather than carpal tunnel syndrome.

    For me, the key to interpreting Dr. Graham’s data or any data about carpal tunnel syndrome is to remember that the popular conception of carpal tunnel syndrome (and therefore that of most health providers) remains wrist and hand pain associated with typing. As science clarifies that carpal tunnel syndrome is best conceived of as objective, verifiable median nerve dysfunction at the carpal tunnel, nonspecific activity-related arm pains will no longer be misplaced in this diagnosis and our understanding and management of both median nerve dysfunction at the carpal tunnel and non-specific activity related arm pain will improve.

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

    References

    1. Brent Graham The Value Added by Electrodiagnostic Testing in the Diagnosis of Carpal Tunnel Syndrome J Bone Joint Surg Am 2008; 90: 2587-2593

    2. Levine DW, Simmons BP, Koris MJ, Daltroy LH, Hohl GG, Fossel AH, Katz JN. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg Am. 1993 Nov;75(11):1585-92.

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