Characteristics of the instrument
The Italian version of CVID-QoL is developed by Quinti et al. in 201510. It consists of 32 items that are most predictive of self-care behaviours, patients’ aspects of the Ig replacement therapy and the features of CVID. The questionnaire is designed to review the situation for the last 3 months. The instrument is a 5-point-likert scale with 0= “never”, 1= “rarely”, 2= “sometimes”, 3= “often” and 4= “always” with higher values generally indicating increasing disability. Total score ranges from 0 (minimum score) to 128 (maximum score); higher scores indicate poorer QoL. It was also identified in percentages as the ratio of the QoL score to the maximum score.