The segmental palmar test in diagnosing carpal tunnel syndrome reassessed

The Impact of Reference Standard on Diagnostic Testing Characteristics for Carpal Tunnel Syndrome: A Systematic Review

Lack of a reliable reference standard for carpal tunnel syndrome (CTS) diagnosis could impact the diagnostic test characteristics. This systematic review sought to evaluate differences in the accuracy of CTS diagnostic modalities based on the reference standard used.

Methods

A systematic review was performed following PRISMA guidelines to investigate diagnostic modalities used in CTS. A literature search of Embase, PubMed, and Cochrane Reviews was conducted for the years of 2010-2021 for primary data, and 113 studies met final inclusion criteria. Studies were stratified based on the reference standard utilized and diagnostic modality assessed, and the weighted means of the sensitivities and specificities were calculated.

Results

Thirty-five studies used clinical diagnosis alone as a reference standard, and 78 studies used electrodiagnostic study (EDS). The specificity for MRI and ultrasound (US) were substantially lower when EDS was used as the reference standard. MRI was the test most affected by the reference standard used, showing increased sensitivity when using EDS as the reference compared to clinical diagnosis (77.1% versus 60.9%) and decreased specificity (87.6% versus 99.2%). Regardless of the reference standard used, all tests had anticipated false-positive and/or false-negative rates of at least 10%.

Conclusions

Testing characteristics vary greatly based on the choice of reference standard, with the sensitivity of MRI most affected. Regardless of reference standard used, EDS, US, and MRI each had false-positive and/or false-negative rates too great to be appropriate for use as a screening examination.

A new method to define cutoff values in nerve conduction studies for carpal tunnel syndrome considering the presence of false-positive cases

BACKGROUND

Nerve conduction studies (NCS) are useful tools for diagnosing carpal tunnel syndrome (CTS). Establishing the normal values is the first step required for utilizing NCS for diagnosis. Previous epidemiological studies demonstrated the presence of fairly large number of false-positive subjects regarding NCS among control population, which has not been properly considered in past studies. This study proposed a new method to address this issue.

METHODS

Non-diabetic 144 CTS patients were retrospectively enrolled using clinically defined inclusion criteria. Controls consisted of 73 age-matched volunteers without hand symptoms. Six NCS parameters were evaluated including peak-latency difference by the thumb method (thumbdif) and that by the ring-finger method (ringdif). The Youden index of the receiver operator characteristic curve was used both to judge the sensitivity of a parameter and to identify false-positive cases that were thought to have subclinical median neuropathy at the wrist. The linear function of six parameters was constructed, and the coefficient for each parameter was variously changed.

RESULTS

When the Youden index took on the maximum value, seven control subjects (10%) were identified as false-positive and were excluded from the calculation of normal values. The most sensitive parameter before exclusion was thumbdif, whereas ringdif became the most sensitive after exclusion. The cut-off value for ringdif was 1.15 ms before exclusion, but was 0.37 ms after exclusion.

CONCLUSION

This method can be widely applied to solve the statistical problem when the gold standard is lacking, and the outside reference standard is not completely reliable.

Motor Nerve Conduction Tests in Carpal Tunnel Syndrome

Background: For the preoperatively often required confirmation of clinically defined carpal tunnel syndrome (CTS), sensory as well as motor nerve conduction studies can be applied. The aim of this study was to test the sensitivity of specific motor nerve conduction tests in comparison with, as well as in addition to, sensory nerve conduction tests.

Methods: In 162 patients with clinically defined CTS, sensory and motor nerve conduction tests were performed prospectively. Sensitivity and specificity of all tests were computed. Also, Receiver Operating Characteristic (ROC) analyses were conducted.

Results: Sensitivity for all sensory tests was at least 79.4% (DIG1). All tests had a specificity of at least 95.7%. The motor conduction test with the highest sensitivity was the TLI-APB (81.3%); its specificity was 97.9%.

Conclusion: In the electrophysiological confirmation of CTS, sensory nerve conduction tests and terminal latency index have a high sensitivity. If, however, sensory nerve action potentials cannot be recorded, all motor nerve conduction tests have a high sensitivity.

Treatment outcome in patients with clinically defined carpal tunnel syndrome but normal electrodiagnostic test results: a randomized controlled trial

Little is known about treatment effect of carpal tunnel release in patients with clinically defined carpal tunnel syndrome (CTS), but normal electrodiagnostic test results (EDX). The aim of this study was to determine whether this category of patients will benefit from surgical treatment. 57 patients with clinically defined CTS and normal EDX were randomized for surgical treatment (n = 39) or non-surgical treatment (n = 18). A six-point scale for perceived improvement as well as the Boston Carpal Tunnel Questionnaire was completed at baseline and at follow-up after 6 months. A significant improvement of complaints was reported by 70.0% of the surgically treated patients and 39.4% reported full recovery 6 months after surgery. Furthermore, both Functional Status Score and Symptom Severity Score improved significantly more in the surgically treated group (p = 0.036 and p < 0.001, respectively). This study demonstrates that most patients with clinically defined CTS and normal EDX results will benefit from carpal tunnel release. Therefore, this group of CTS patients must not a priori be refrained from surgery.

Comparison of peak versus onset latency measurements in electrodiagnostic tests for carpal tunnel syndrome

PURPOSE

The aim of this prospectively conducted study was to compare the diagnostic accuracy of onset versus peak latency measurements of sensory nerve action potentials in electrodiagnostic studies in diagnosing carpal tunnel syndrome.

METHODS

In 156 consecutive patients with clinically defined carpal tunnel syndrome, standardized nerve conduction studies (DIG1, DIG4, PALM3) were performed. Both onset and peak latency were measured. Sensitivity was calculated using the clinical diagnosis as golden standard. Bland-Altman plots were constructed to assess the agreement for quantitative measurements. Overall agreement, positive and negative percent agreement, and Kappa coefficient were computed.

RESULTS

The Bland-Altman plots, positive and negative percent agreement show good overall agreement. The kappa coefficient was 0.850, 0.847, and 0.815 for DIG1, DIG4, and PALM3, respectively.

CONCLUSIONS

Onset and peak latencies used in electrodiagnostic tests show a good overall agreement in confirming the clinical diagnosis of carpal tunnel syndrome. Because onset latency measurement represents nerve conduction velocity of the fastest conducting fibers, the use of onset latencies is recommend. In case of uncontrollable stimulus artifacts, peak latencies may be used instead.

Bifid median nerve in carpal tunnel syndrome: do we need to know?

INTRODUCTION

We tested the hypothesis that a bifid median nerve predisposes to development of carpal tunnel syndrome (CTS) and investigated differences in electrophysiological findings and outcome.

METHODS

A total of 259 consecutive patients with clinically defined CTS were included and investigated clinically, electrophysiologically, and ultrasonographically. Fifty-four healthy asymptomatic volunteers were investigated ultrasonographically.

RESULTS

The prevalence of bifid median nerves is equal in patients with CTS and controls. Electrophysiological and ultrasonographic abnormalities are more pronounced in patients with non-bifid median nerves. Some outcome data are better in patients with non-bifid median nerves, but others do not show significant differences.

CONCLUSIONS

A bifid median nerve is not an independent risk factor for development of CTS. Some of our data suggest outcome after surgical decompression to be different, but others do not. The surgical technique in these patients may therefore have to be reevaluated.