Development and validation of a self-administered systemic sclerosis questionnaire (SySQ)

Objective. To develop a self-administered systemic sclerosis questionnaire (SySQ) covering condition-specific functional limitation and symptoms. Methods. An initial item pool was generated by open patient interviews. A preliminary questionnaire was devised using 62 systemic sclerosis (SSc; scleroderma) patients. Factor analysis was used for further selection and grouping of items into distinct scales. The retrieved scales were tested for internal consistency and test-retest reliability. Spearman's rank correlation and Wilcoxon's rank sum test were used to examine hypothesized associations of the SySQ with various clinical and laboratory features. Results. Altogether 32 SySQ items were selected and aggregated into 12 scales addressing 'pain', 'stiffness', 'coldness', 'complex functions', 'strength of hands', 'rising', 'walking', 'shortness of breath', 'upper airway symptoms', 'eating', 'swallowing' and 'heartburn/regurgitation'. Internal consistency ranged from 0.93 ('complex functions') to 0.73 ('heartburn/regurgitation'); Spearman's correlation coefficient for test-retest reliability ranged from 0.93 to 0.73 (P < 0.001). While the scales were associated with corresponding functional impairments, there was generally less association with morphological impairments. Conclusion. The SySQ is a valid and reliable condition-specific measure in patients with SSc. Individually applicable scales cover a wide spectrum of general and organ-specific SSc symptoms and functional limitation. After further validation with respect to its ability to measure change, it may be used in clinical, health services and epidemiological research.