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Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Objective

We developed a modified Phalen's test (MPT), which uses sensory testing in Phalen's position, as a diagnostic screening tool for carpal tunnel syndrome (CTS). This study was designed to determine the sensitivity, specificity, and receiver operating characteristic (ROC) curve of the MPT for diagnosis of CTS.

Methods

Electrodiagnostic nerve conduction studies (EDS) were used as the gold standard. MPT was performed by a blinded examiner on patients prior to EDS. MPT was recorded as either positive or negative based on the presence or absence of a median nerve sensory deficit while the hand was in Phalen's position.

Results

Sixty-six hands were included in this study. Chi-square for the MPT compared to EDS as the gold standard was 41.449 (P < 0.001), and the validity coefficient (phi) was 0.792 (P < 0.01). The traditional Phalen's test (TPT) compared to the EDS demonstrated a chi-square of 15.349 (P < 0.001) and a phi coefficient of 0.482 (P < 0.01). ROC curve estimates for the MPT revealed a sensitivity of 84.4% compared to 50% for the TPT. The standard error of the estimate for sensitivity was 3.3% for the MPT and 5.8% for the TPT.

Conclusion

The MPT is a highly useful screening diagnostic tool for CTS. The MPT demonstrates greater accuracy than the TPT for predicting CTS. The MPT also demonstrates greater sensitivity than the TPT in predicting a positive electrodiagnostic test for CTS.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Carpal tunnel syndrome (CTS) is caused by elevated pressure in the carpal tunnel. Prolonged or frequent episodes of elevated pressure in the carpal tunnel may result in segmental demyelination associated with sensory symptoms and occasionally with weakness. When there is prolonged ischemic axonal injury, nerve dysfunction may be irreversible (1, 2).

Electrodiagnostic study (EDS) for CTS is highly specific, reasonably sensitive (3), and helps rule out other causes of similar signs and symptoms. EDS (nerve conduction, needle electromyography) continues to be the mainstay of laboratory diagnosis of CTS. Furthermore, some third-party payers require EDS before compensating claims. Consensus committees from professional societies have endorsed EDS as the diagnostic test of choice. However, since EDS costs $800 to $1,600, clinical history and physical examination including provocative tests are the most appropriate initial diagnostic tools in the ambulatory setting. The predictive value of these tests, however, is disputed. The sensitivity of Phalen's test and Tinel's test is reported to be between 25% and 75%, with specificities between 70% and 90% (4–7). The sensitivity of sensory testing using Semmes-Weinstein monofilament testing may be as high as 91%, and combining this test with Phalen's test may have a specificity of 86% (8, 9).

Koris et al (10) studied combining Semmes-Weinstein monofilament sensory testing during the wrist flexion provocational test (Phalen's maneuver) in a group of 21 patients (33 hands) with electrodiagnostically verified CTS and 30 asymptomatic hands (controls). The combined test demonstrated a sensitivity of 82% and a specificity of 86%. It was more sensitive and specific than the wrist flexion test (Phalen's test) alone and more specific than sensory testing alone. Unfortunately, this combined test has not been widely applied clinically, likely due to the complexity of the approach taken by Koris et al requiring several sensory threshold monofilament measurements.

The purpose of our study was to evaluate the validity, sensitivity, and specificity of a simplified version of the modified Phalen's test (MPT) that we have developed. The goal was the development of a highly accurate and easy to perform screening diagnostic tool for CTS.

Materials and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

The MPT combines the traditional Phalen's test with simultaneous objective sensory examination of the hand with a standard monofilament. The traditional Phalen's test is considered positive if paresthesiae are reproduced during the maneuver of holding the wrists in a position of fixed flexion for 1 minute. The MPT places the hands as in Phalen's test while performing sensory testing with a Semmes-Weinstein 2.83-unit monofilament applied perpendicular to the skin surface until it bends (Figure 1). The monofilament was applied to the palmar surface and lateral side of each finger's distal phalanx 3 times. MPT was considered positive if the subject did not register the touch in any 1 or more fingers in a median nerve distribution (radial 3.5 fingers on the palmar side). The MPT was considered negative if the subject correctly registered a touch. The palmar surface of the fifth finger's distal phalanx was used as a control. The patient's hands were maintained in the flexed position throughout the testing interval.

thumbnail image

Figure 1. Modified Phalen's test consists of the traditional Phalen's test maneuver of holding the wrists in a position of fixed flexion and the use of a Semmes-Weinstein 2.83-unit monofilament. The filament (arrow) is applied perpendicular to the skin surface until it bends.

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Testing was performed in a standardized fashion by 1 of 2 trained examiners (SB, SAA). The examiner was blinded to the diagnosis. The testing was performed prior to EDS of the upper extremity in a neurology clinic. The inclusion criterion was adults ages 18 years or older. Exclusion criteria consisted of 1) cervical radiculopathy, 2) previous history of stroke, 3) diabetes mellitus, and 4) concomitant neck injury.

Sixty-six hands of 37 patients were studied prospectively from June 2007 to July 2008. Eleven men and 26 women who were between the ages of 27 and 88 years were included in this study. Hands were tested by both the traditional Phalen's test and the MPT. Our gold standard determination of normal hands or hands with CTS was based on EDS results. EDS was considered positive for CTS if the median versus ulnar orthodromic sensory (mixed) peak latency measurement with midpalmar stimulation at 8 cm recording from the wrist showed a difference of 0.4 msec or more. Among 37 patients, 8 patients had EDS on only 1 hand. The remainder of the patients underwent EDS in both hands. Data were analyzed using chi-square analysis and the resultant phi coefficient to determine the validity of MPT compared to EDS. Receiver operating characteristic (ROC) curves were calculated to determine the associated specificity and sensitivity of the MPT.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

To determine the concurrent validity of the MPT compared to EDS, 66 hands were studied. Of those 66 hands, 46 were found to have CTS and 20 were normal by EDS. Of these 46 hands with documented CTS, the traditional Phalen's test was positive for 23 hands (Table 1), whereas the MPT was positive in 39 hands (Table 2). Also, the MPT produced significantly fewer false-negative tests (7 hands) when compared to the traditional Phalen's test (23 hands). There were no false-positive results using either the traditional Phalen's test or the MPT. The validity of the traditional Phalen's test and the MPT was calculated using standard 2 × 2 chi-square analyses (Table 3). Both the traditional Phalen's test (χ2 = 15.35) and the MPT (χ2 = 41.45) were found to be valid; however, the MPT was more accurate (ϕ = 0.79) at predicting CTS compared to the traditional Phalen's test (ϕ = 0.48). Sensitivity and specificity of the 2 tests were analyzed using ROC curve analysis techniques to further examine the accuracy of the 2 measures compared to EDS (Table 4). Both the traditional Phalen's test and the MPT were found to be 100% specific for the diagnosis of EDS. The MPT, however, had a greater degree of sensitivity (85%) compared to the traditional Phalen's test (50%), as shown in Figure 2. Furthermore, the standard error of the estimate for sensitivity was lower for the MPT (3.3%) compared to the traditional Phalen's test (5.8%). Therefore, the MPT was more sensitive.

Table 1. Validity of Phalen's test compared to EDS*
 Negative EDSPositive EDS
  • *

    Values are the number of hands. Traditional Phalen's test: χ2 = 15.35, ϕ = 0.48, P < 0.01. EDS = electrodiagnostic study.

Negative Phalen's test2023
Positive Phalen's test023
Table 2. Validity of the MPT compared to EDS*
 Negative EDSPositive EDS
  • *

    Values are the number of hands. Modified Phalen's test (MPT): χ2 = 41.45, ϕ = 0.79, P < 0.01. EDS = electrodiagnostic study.

Negative MPT207
Positive MPT039
Table 3. Validity of the traditional Phalen's test and modified Phalen's test compared to electrodiagnostic study
Variableχ2ϕ
  • *

    Significant at P < 0.01.

Traditional Phalen's test15.350.48*
Modified Phalen's test41.450.79*
Table 4. Receiver operating characteristic curve analyses of the traditional Phalen's test and modified Phalen's test
VariableSpecificity, %Sensitivity, %
Score95% confidence intervalScore95% confidence interval
Traditional Phalen's test10080–1005035–65
Modified Phalen's test10080–1008571–93
thumbnail image

Figure 2. Receiver operating characteristic curves showing sensitivity and specificity of the traditional Phalen's test and modified Phalen's test.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Recent advances in understanding the pathophysiology of CTS favor the concept that reduced microvascular perfusion plays a major role in the early stages of median nerve entrapment neuropathy. In patients with CTS, wrist flexion results in increased pressure in the carpal tunnel, which in turn exacerbates existing intraneural ischemia and results in a profound conduction block (1, 2, 11). It has been shown that abnormalities detected by threshold sensory testing provide a sensitive indicator of clinically significant nerve compression (4). Koris et al (10) used multiple sensory threshold monofilament sensory testing of the hand both in neutral and Phalen's positions. The complexity of this approach is not suitable to a busy outpatient setting. In contrast, MPT is very simple and easy to perform. The result of our study is comparable with the study performed by Koris et al (10). Our study demonstrates that the MPT is a highly useful screening diagnostic tool for CTS. The MPT is much more sensitive than the traditional Phalen's test. It improved the sensitivity of the traditional Phalen's test by 35%, and the MPT is, therefore, less likely to result in a false-negative diagnosis. The MPT is a very simple test that can be easily performed by primary care physicians with no significant patient discomfort.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Bilkis had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Bilkis, Loveman, Ali, Kadir, McConathy.

Acquisition of data. Bilkis, Loveman, Eldridge, Ali, Kadir.

Analysis and interpretation of data. Bilkis, Loveman, Eldridge, McConathy.

REFERENCES

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES