Objectives: The objective of this article is to validate the Lupus Impact Tracker (LIT), a disease-specific patient-reported outcome (PRO) tool, in systemic lupus erythematosus (SLE) patients in a multi-ethnic Australian cohort.
Methods: Patients attending the Monash Lupus Clinic were asked to complete the LIT, a 10-item PRO. Psychometric testing assessing criterion validity, construct validity, test-retest reliability (TRT) and internal consistency reliability (ICR) were performed. We compared the LIT scores across patient characteristics, and correlations between LIT scores and SLEDAI-2k, PGA, and SLICC-SDI were examined.
Results: LIT data were obtained from 73 patients. Patients were 84% female with a median age of 41 years, and 34% were Asian. The cohort had mild-moderate disease activity with a median (IQR) Systemic Lupus Erythematosus Disease Activity Index-2000 (SLEDAI-2k) of 4 (IQR 2-6). The median LIT score was 32.5 (IQR 17.5-50). LIT demonstrated criterion validity against SLEDAI-2k and SDI. Construct validity assessed by confirmatory factor analysis demonstrated an excellent fit (Goodness of fit index 0.95, Comparative Fit Index 1, Root Mean Square Error of Approximation <0.0001). The LIT demonstrated TRT with an overall intraclass correlation coefficient of 0.986 (95% CI 0.968-0.995). ICR was demonstrated with a Cronbach's alpha of 0.838. Patients with disability, low socioeconomic status, or higher disease activity had significantly worse LIT scores.
Conclusion: The LIT demonstrated properties consistent with its being valid in this population. Lower socioeconomic status appears to have a significant impact on patient-reported health-related quality of life in SLE.
Keywords: Australia; patient-reported outcomes; quality of life; systemic lupus erythematosus.
© The Author(s) 2016.