title: The construct validity and responsiveness of sensory tests in patients with carpal tunnel syndrome.
abstract: OBJECTIVE
  Sensory evaluation is fundamental to evaluation of patients with Carpal Tunnel Syndrome (CTS). The purpose of this study was to determine the construct validity and responsiveness for sensory threshold tests in patients with CTS.
  
  
  METHODS
  Sixty-three patients diagnosed with CTS were evaluated prior to orthotic intervention and again at follow up at 6 and 12 weeks. Sensory tests included touch threshold PSSD (Pressure Specified Sensory Device) and vibration threshold (Vibrometer). Construct validity was assessed by comparing sensory tests to hand function, and dexterity testing using Spearman rho (rs). Patients were classified as either responders or non-responders to orthotic intervention based on the change score of the Symptom Severity Scale (SSS) of 0.5. Responsiveness of the sensory tools was measured using ROC (receiver operating characteristic) curves, SRM (Standardized Response Mean), and ES (Effect Sizes).
  
  
  RESULTS
  The PSSD had low to moderate correlations (rs ≤ 0.32) while Vibrometer scores had moderate correlations (rs = 0.36 - 0.41) with dexterity scores. The Clinically Important Difference (CID) for the PSSD was estimated at 0.15 g/mm(2) but was not discriminative. The Vibrometer demonstrated moderate responsiveness, with a SRM = 0.61 and an ES = 0.46 among responders. The PSSD had a SRM = 0.09 and an ES = 0.08 and showed low responsiveness for patients with a clinically important improvement in symptoms.
  
  
  CONCLUSIONS
  Measurement properties suggest that the Vibrometer was preferable to the PSSD because it was more correlated to hand function, and was more responsive. Clinicians may choose use the Vibrometer opposed to the PSSD for determining important change in sensation after orthotic intervention.
authors.affiliation: Health and Rehabilitation Sciences Physical Therapy, Faculty of Health Sciences, Western University, London, Ontario, Canada.
authors.forename: Derek K M
authors.initials: DK
authors.lastname: Cheung
authors.affiliation: Hand and Upper Limb Clinic, St. Joseph's Hospital, London, Ontario, Canada ; School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada.
authors.forename: JoyC
authors.initials: J
authors.lastname: MacDermid
authors.affiliation: Health and Rehabilitation Sciences Physical Therapy, Faculty of Health Sciences, Western University, London, Ontario, Canada.
authors.forename: Dave
authors.initials: D
authors.lastname: Walton
authors.affiliation: Hand and Upper Limb Clinic, St. Joseph's Hospital, London, Ontario, Canada ; Schulich School of Medicine, Western University, London, Ontario, Canada.
authors.forename: Ruby
authors.initials: R
authors.lastname: Grewal
keywords: Carpal tunnel syndrome; clinically important difference; construct validity; orthotic intervention; psychometric properties; responsiveness; touch threshold; vibration threshold.