Diagnosis of Carpal Tunnel Syndrome: Effectiveness of Diagnostic Tests. Clinical Trial of Accuracy
Condition: Carpal Tunnel Syndrome; Compression Neuropathy, Carpal Tunnel; Median Neuropathy, Carpal Tunnel
MeSH terms: Carpal Tunnel Syndrome; Charcot-Marie-Tooth Disease; Nerve Compression Syndromes; Hereditary Sensory and Motor Neuropathy; Median Neuropathy; Syndrome
Study type: Interventional

Summary: 
      There is no golden universal standard for the diagnosis of Carpal Tunnel Syndrome (CTS). In
      this scenario, for a comparison of the effectiveness of the principal diagnostic tests CTS
      should determine how they affect the likelihood of disease through a clinical accuracy trial
      of good methodological quality in order to get answers to what is the best diagnostic
      strategy in clinical CTS practice. The paresthesia in nerve distribution territory median
      hands is the most common symptom in patients with CTS. The nuisance caused by paresthesia
      directly affects the quality of life of patients and impairs daily manual activities and
      sleep quality. To evaluate the remission of paresthesia is a major clinical criterion for
      improved STC being an expected relevant outcome for the patient. This study evaluated and
      compared the diagnostic accuracy of the ultrasonography (US) and electromyography (EMG),
      considering the postoperative status of remission of paresthesia as the reference standard in
      the diagnosis of CTS.
    

Detailed description: 
      Carpal tunnel syndrome (CTS) is characterized by median nerve compression at the level of the
      wrist. It represents 90% of compressive neuropathies and is the most common upper member. For
      being a major cause of disability in hands, the early and accurate diagnosis to obtain a
      definitive treatment in CTS is essential. Despite this, there is no consensus on which is the
      most effective diagnostic criteria for CTS. The absence of a reference standard universally
      accepted for the diagnosis of CTS contributes to this scenario.

      Ultrasonography (US) and electromyography (EMG) are the complementary examinations most often
      used in the diagnosis of CTS, but overestimated in their performance and require caution in
      interpreting the results, particularly the lack of a consensus on the ideal cutoff point for
      considering the diagnosis of CTS. This results in a wide variation in results of sensitivity
      and specificity for these tests, both the EMG (sensitivity = 82 to 98% and specificity = 19
      to 88%) and for the US (sensitivity = 70 to 98% and specificity = 63 to 100%), in addition to
      a high proportion (20-40%) of false-negative and false-positive.

      Most diagnostic accuracy studies at CTS compare the results of the US with EMG, considering
      most of the time the EMG as reference standard. There are few studies comparing the results
      of the US and EMG using other benchmarks, such as the degree of clinical improvement after
      surgical treatment of CTS or a combination of clinical signs and symptoms. The value of
      diagnostic tests for CTS can be established by comparing the diagnostic strategies and
      studying how they can affect the likelihood of STC. This spectrum can be considered the
      results of surgical treatment as the reference standard, as these are directly related to the
      diagnosis of CTS. Surgical treatment by classical open surgery is the definitive treatment of
      CTS and provides relief from symptoms, mainly the remission of paresthesia, with satisfactory
      results in up to 98% of the cases. The discomfort caused by paresthesia in the quality of
      life of patients and impairs daily manual activities and the quality of sleep is considerable
      in CTS. The remission of paresthesia is a clinical improvement parameter of the disease being
      an expected and relevant outcome for the patient. Primary and well-designed controlled
      studies with good methodological quality to guide the diagnostic practices and evaluate their
      effectiveness in an integrated manner in carpal tunnel syndrome (CTS) are unusual and
      challenging in the current literature. This study, innovative in its method has as primary
      objective to compare the accuracy of ultrasonography in relation electromyography in the
      diagnosis of carpal tunnel syndrome, using to the results of the surgical treatment as the
      reference standard.

      The study design is a clinical trial of accuracy, primary, longitudinal, controlled,
      prospective, and performed in a single center. This clinical trial follows the accuracy STARD
      recommendations (Standards for Reporting of Diagnostic Accuracy).

      Patients with clinical suspicion of CTS, who were referred and attended consecutively in our
      specialty clinic in hand surgery, were submitted to an initial clinical evaluation (ACI), by
      a same specialist in hand surgery, who used the CTS-6 clinical diagnostic instrument of
      GRAHAM et al. (2006), represented by a logistic regression model that estimates the
      diagnostic probability of CTS based on the presence or absence of the 6 diagnostic criteria
      that are: paresthesia, night paresthesia, weakness and/or atrophy thenar musculature, Tinel
      signal, Phalen test and loss of 2-points discrimination.

      Diagnostic intervention of the US and EMG were performed by the same professional in each
      area, both experienced and specialized in their acting area, who were unaware of the clinical
      situation of patients at the time of the tests.

      The ultrasonography (US) of the wrist were performed in a Philips brand equipment (model
      M2540A, Bothell, WA USA) with broadband linear transducers. The US examination technique
      consisted of the positioning of the patient comfortably, sitting with forearm in a supine
      position in slight flexion supported on the examination table, with the handle in neutral
      position and the hand with the fingers in extension. In order to assess the accuracy of the
      US in the diagnosis of CTS, a cutoff value equal to and greater than 10.0 mm² of the median
      nerve transverse cross-sectional area was considered at the proximal limit of the carpal
      tunnel.

      The electromyography (EMG) of the upper limbs were performed on Nihon Kohden brand equipment
      (model MEB 9400K, 2 channels, Tokyo, Japan). The EMG technique consisted of the positioning
      of the patient comfortably, in a horizontal dorsal decubitus position with the head resting
      on a high headboard on the examination table and with the upper limbs positioned at rest
      along the body. The objective of the EMG was to determine the sensory conduction velocity of
      the median nerve in the third finger-cuff segment at a distance of 13 cm, with a cut-off
      value of less than 50 m/s and a higher value or equal to 4.2 ms for distal motor dormancy of
      the median nerve of the wrist to the tenar eminence (short abductor muscle of the thumb).

      After the examinations of US and EMG, the patients were referred and submitted surgical
      treatment by classical open pathway, by a same surgeon. Outpatient surgeries were performed
      at the surgical center of the Vale do Paraíba Regional Hospital in Taubaté - SP. The
      anesthesia technique used was Bier's regional endovenous. Each patient was followed monthly
      until the fourth postoperative month.

      To analyze the accuracy of the diagnostic tests of US and EMG in relation to the reference
      standard (remission of paresthesia), the McNemar test and the 2x2 contingency table were
      used, using as reference standard the improvement of paresthesia. The evolution of the Boston
      score by moments of evaluation and diagnostic results was evaluated using the analysis of
      variances (Anova) with repeated measures. Comparison of the means of the two groups was
      performed using the Student's t-test for independent samples. The analyzes were performed
      using the statistical package SPSS 20.0 and Stata 12. For all statistical tests, a
      significance level of 5% was adopted. The statistical sampling was performed considering a
      20% difference between the sensitivity of the EMG and US diagnostic tests using the McNemar
      test, with a statistical power of 84.0% and a significance level of 5%. For this calculation,
      the value of 60% and a prevalence of 80% for STC were assumed as a percentage of total
      agreement, requiring a total sample of 115 patients. A further 5% of all patients were
      recruited to cover possible losses or exclusions during the course of the study. Statistical
      software PASS 14 (Power Analysis and Sample Size System) - NCSS was used.

      There is a lack of accuracy of properly designed studies with good quality evidence to
      recommend good diagnostic practices in CTS. This study presents the innovative proposal of
      conducting a clinical trial of accuracy, specifically designed when there is no reference
      standard defined for the diagnosis of the CTS, using the reference paresthesia after surgery
      as a relevant outcome from the standpoint of the patient. The use of more accurate diagnostic
      criteria with a more effective diagnostic protocol for the clinical examination, the US and
      the EMG, based on a high level of evidence will lead directly into the paradigm shift for
      clinical decision-making, effective and safe CTS treatment.
    

Intervention name(s): accuracy diagnostic
Intervention type(s): Diagnostic Test
Intervention description(s): effectiveness of the ultrasonography and electromiography for best performance and diagnostic accuracy in carpal tunnel syndrome
Other intervention name(s): accuracy of the ultrasonography; accuracy of the electromiography
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: carpal tunnel syndrome; clinical examination; diagnosis; clinical trial; median nerve compression; accuracy; ultrasonography; electromyography; electrodiagnostic testing