Background/Purpose: As part of an NIH sponsored effort to develop a data-driven CRISS, we evaluated the face, content, and construct validity (convergent and discriminant) of patient (Pt) and physician (MD) assessments for use as the “external gold standards” or “anchors” to compare against individual core set items developed as part of a consensus meeting conducted by the Scleroderma Clinical Trial Consortium (Khanna D, Ann Rheum Dis 2008). This methodology has been used for developing other response criteria.

Methods:  We recruited patients with early diffuse SSc (< 5 years) at four scleroderma centers in the United States. Pre-defined outcome measures were collected. These included demographics (e.g., age, disease duration), patient-reported outcomes (e.g., HAQ-DI, SF-36), physical examination (e.g., skin score, joint count), and physiological/ radiological tests (e.g. echocardiogram, pulmonary function tests).  We assessed the test characteristics of 8 potential Likert anchors (3 MD-derived: global assessment; activity of skin involvement; severity of skin involvement and 5 Pt. derived: patient global assessment ; activity of skin involvement; limitations due to skin involvement; overall pain; transition question regarding overall health)  against the above measures. The associations between anchors and outcome measures were assessed using Spearman correlation. The discrimination between the anchors (trichotomized) and outcome measures was assessed using parametric or non-parametric tests. Each anchor was ranked (1[weakest]-8 [best]) based on the strength of the correlation (convergent validity) and significance of p value for trichotomized variables (discriminant validity) vs. each outcome measure. Due to skewness in the distributions, the median of the rankings for each anchor was used to identify anchors with the best convergent and discriminant validity.

 Results: 200 patients completed the baseline visit. The mean (SD) age was 50 (11.9) yrs, disease duration was 2.4 (1.6) yrs, modified Rodnan skin score was 20.6 ( 10.1), and HAQ-DI was 0.96 ( 0.79). All 8 anchors have face validity. MD global, Pt. global, and Pt-activity skin have content validity as they assess overall SSc/ skin involvement [major feature of the SSc]. There were high correlations between the 3 MD anchors (r= 0.57-0.69) but wide variation for  pt. anchors (r=0.17-0.58). The pt. anchors complemented MD anchors (r=0.18-0.47).  Among the MD-administered anchors, global assessment had the best convergent and discriminant validity (Table). Of the patient-administered anchors, patient global assessment and pain had the best convergent and discriminant validity (Table).

*Higher number denotes higher median ranking

Conclusion: All anchors (except transition anchor) have high convergent and discriminant validity. These measures will serve as key anchors in the analysis of the CRISS longitudinal database and the development of a composite index.