Reliability and repeatability of the hoffmann sign

Abstract

Objective: Objective of the study was to determine interrater, intrarater, and intrasubject reliability of the Hoffmann sign. Design(s): This was a cross-sectional, observational, repeated-measures study. Setting(s): Hospital-based inpatient spinal cord injury (SCI) unit, SCI, and PM&R clinics. Participant(s): Any willing participant recruited from the above locations was enrolled. Exclusion criteria: amputation involving 1st through 3rd fingers, relapsing remitting multiple sclerosis, or any acute central neurologic illness or injury requiring hospital admission. Local institutional review board approval was obtained. Power analysis revealed a minimum sample size of 86 hands (or 43 subjects) to achieve adequate statistical power, with assumed overall incidence of a positive Hoffmann sign at 3%. Intervention(s): Hoffmann sign was elicited by using a predetermined, standardized technique by all investigators: 1 primary and 3 secondary. Hoffmann sign was considered positive if there was any reflexive flexion of the distal phalanx of the thumb or any of the fingers. One primary and one secondary examiner elicited the Hoffmann sign on both hands of each subject twice, with up to 10 repetitions allowed per trial. Repeated testing was done in the same fashion on each subject on another day. Main Outcome Measure(s): Kappa values were calculated between investigator pairs per hand per subject, per trial to determine interrater reliability. Intrarater reliability was calculated per hand per investigator per session between the 2 trials. Intrasubject reliability was determined per hand, per investigator, across the 2 sessions. Result(s): Data were collected from 47 of 53 subjects who completed the study. All kappa values were obtained with P< .01. Interrater kappa was 0.65 (189 pairs), intrarater kappa was 0.89 (380 pairs), and intrasubject kappa was 0.69 (90 pairs). Conclusion(s): The Hoffmann sign has excellent interrater, intrarater, and intrasubject reliability when tested by using predetermined, standardized technique, across a diverse subject population. Further studies are needed to determine its reliability in different clinical settings and techniques.