Background: In upper-limb peripheral nerve injured patients, cold intolerance is the most bothersome, prolonged and disabling symptom, negatively affecting work and leisure activities. The Cold Intolerance Symptom Severity (CISS) questionnaire is widely used to assess this symptom, though its psychometric properties have not been examined in depth and no validated Italian version exists.
Aim: The aim of this study was to examine in depth the psychometric properties of the Italian version of CISS (CISS-It) in a sample of patients with upper-limb peripheral nerve injury.
Design: Prospective cross-sectional.
Setting: Outpatient.
Population: Seventy-two subjects with upper-limb peripheral nerve injury consecutively admitted for outpatient assessment and rehabilitation.
Methods: We assessed dimensionality, reliability, validity, and responsiveness (minimum detectable change, MDC) of the CISS-It by means of Classical Test Theory methods.
Results: Factor analysis confirmed the scale's unidimensionality. Internal consistency (alpha=0.93) and test-retest reliability (ICC2,1 =0.96) were high. The convergent validity of the CISS-It was demonstrated by its correlations with the 4-item Douleur Neuropathique (DN4) Scale (rs=0.73), pain score (rs=0.61), and Medical Research Council (MRC) Scale for sensory function (rs=-0.44). The MDC95 was 11.30 points.
Conclusions: CISS-It is a reliable, valid and easy-to-use questionnaire for measuring cold intolerance in subjects with upper-limb peripheral nerve injury. However, there is room for some refinement of the CISS structure and wording, which we suggest to perform within the framework of modern statistical methods (such as Rasch analysis), in order to optimize content coverage and technical quality of the measurement.
Clinical rehabilitation impact: This examination in depth of the psychometric properties of the CISS further increases confidence in the scale's use for clinical assessment and monitoring of abnormal cold sensitivity in the rehabilitation of patients with upper extremity peripheral nerve injury.