title: A study of interpolation method in diagnosis of carpal tunnel syndrome.
abstract: BACKGROUND
  The low correlation between the patients' signs and symptoms of carpal tunnel syndrome (CTS) and results of electrodiagnostic tests makes the diagnosis challenging in mild cases. Interpolation is a mathematical method for finding median nerve conduction velocity (NCV) exactly at carpal tunnel site. Therefore, it may be helpful in diagnosis of CTS in patients with equivocal test results.
  
  
  OBJECTIVE
  The aim of this study is to evaluate interpolation method as a CTS diagnostic test.
  
  
  METHODS
  Patients with two or more clinical symptoms and signs of CTS in a median nerve territory with 3.5 ms ≤ distal median sensory latency <4.6 ms from those who came to our electrodiagnostic clinics and also, age matched healthy control subjects were recruited in the study.
  
  
  METHODS
  Median compound motor action potential and median sensory nerve action potential latencies were measured by a MEDLEC SYNERGY VIASIS electromyography and conduction velocities were calculated by both routine method and interpolation technique.
  
  
  METHODS
  Chi-square and Student's t-test were used for comparing group differences. Cut-off points were calculated using receiver operating characteristic curve.
  
  
  RESULTS
  A sensitivity of 88%, specificity of 67%, positive predictive value (PPV) and negative predictive value (NPV) of 70.8% and 84.7% were obtained for median motor NCV and a sensitivity of 98.3%, specificity of 91.7%, PPV and NPV of 91.9% and 98.2% were obtained for median sensory NCV with interpolation technique.
  
  
  CONCLUSIONS
  Median motor interpolation method is a good technique, but it has less sensitivity and specificity than median sensory interpolation method.
authors: Department of Physical Medicine and Rehabilitation, Shiraz University of Medical Sciences, Shiraz, Iran ; Burn Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
authors: Alireza
authors: A
authors: Ashraf
authors: Abbas
authors: A
authors: Daghaghzadeh
authors: Mahshid
authors: M
authors: Naseri
authors: Aref
authors: A
authors: Nasiri
authors: Maryam
authors: M
authors: Fakheri
keywords: Carpal tunnel syndrome; electrodiagnosis; interpolation; nerve conduction velocity