Linguistic, psychometric validation and diagnostic ability assessment of an Italian version of a 19-item wearing-off questionnaire for wearing-off detection in Parkinson’s disease
A patient self-rated 19-item wearing-off questionnaire (WOQ-19) was shown to be a potent screening tool for wearing-off (WO) in patients with Parkinson’s disease. As part of the early detection of wearing-off in Parkinson’s disease study, we preliminarily performed a linguistic and a psychometric validation of an Italian version of the WOQ-19. Moreover, we assessed the sensitivity and specificity of the WOQ-19 in the office-based settings. The psychometric validation study included assessment of discriminant ability, internal consistency and test–retest reliability. The intraclass correlation coefficient (ICC) and the Cronbach’s Alpha were assessed. The WOQ-19 sensitivity and specificity were calculated in respect to the physician assessment of WO, taken as the gold standard. The Italian version of WOQ-19 was found easy to understand by ≥80% of the patients. The number of WO-related symptoms detected by WOQ-19 was 7.5 ± 3.2 in patients with WO and 1.6 ± 2.6 in patients without WO (p < 0.0001). Cronbach’s alpha was equal to 0.868 for the total number of WO symptoms. The ICC value was equal to 0.858 for WO-related symptoms as a whole. The diagnostic ability study recruited 207 patients: for a WOQ-19 cut-off ≥2, the sensitivity was equal to 0.881 and the specificity was 0.674. This is the first validation of WOQ-19 in Italian, with excellent linguistic validity and psychometric properties. WOQ-19 was confirmed to be reliable in WO detection.