The long-form 64-item Profile of Fatigue and Discomfort--Sicca Symptoms Inventory (PROFAD-SSI) questionnaire was developed as a patient-reported assessment tool for use in primary SS (PSS) and other rheumatic disorders. In this study, we assess whether the (shorter and more practical) 19-item PROFAD-SSI-SF (short form) gives similar results and whether a still briefer version using visual analogue scales (VASs) is feasible.
Questionnaire surveys comprising the long and short versions of the PROFAD-SSI were mailed to 43 patients with PSS and 50 patients with RA, who were asked to complete these contemporaneously as well as repeating the process 1 month later. PSS patients also completed a series of VASs comprising fatigue and sicca domains of the SSI.
Surveys were returned from 35 PSS patients and 35 RA patients. All domains of the long- and short-form PROFAD-SSI showed strong correlations (Spearman rho between 0.779 and 0.996, P < 0.01). Factor analysis generally confirmed the previously validated domain structure with Cronbach's alpha = 0.99. The PROFAD-SF somatic fatigue domain correlated more strongly with a fatigue VAS than did the mental fatigue domain. The SSI-SF domain scores correlated with equivalent VAS scores.
The long- and short-form PROFAD-SSI questionnaires correlate closely suggesting that the PROFAD-SF is valid as an outcome tool. Preliminary data also suggest that an even briefer form with compression of the domains into single VAS is also feasible.