Development, Sensibility, and Validity of a Systemic Autoimmune Rheumatic Disease Case Ascertainment Tool

Case ascertainment through self-report is a convenient but often inaccurate method to collect information. The purposes of this study were to develop, assess the sensibility, and validate a tool to identify cases of systemic autoimmune rheumatic diseases (SARD) in the outpatient setting.

The SARD tool was administered to subjects sampled from specialty clinics. Determinants of sensibility - comprehensibility, feasibility, validity, and acceptability - were evaluated using a numeric rating scale from 1-7. Comprehensibility was evaluated using the Flesch Reading Ease and the Flesch-Kincaid Grade Level. Self-reported diagnoses were validated against medical records using Cohen's κ statistic.

There were 141 participants [systemic lupus erythematosus (SLE), systemic sclerosis (SSc), rheumatoid arthritis, Sjögren syndrome (SS), inflammatory myositis (polymyositis/dermatomyositis; PM/DM), and controls] who completed the questionnaire. The Flesch Reading Ease score was 77.1 and the Flesch-Kincaid Grade Level was 4.4. Respondents endorsed (mean ± SD) comprehensibility (6.12 ± 0.92), feasibility (5.94 ± 0.81), validity (5.35 ± 1.10), and acceptability (3.10 ± 2.03). The SARD tool had a sensitivity of 0.91 (95% CI 0.88-0.94) and a specificity of 0.99 (95% CI 0.96-1.00). The agreement between the SARD tool and medical record was κ = 0.82 (95% CI 0.77-0.88). Subgroup analysis by SARD found κ coefficients for SLE to be κ = 0.88 (95% CI 0.79-0.97), SSc κ = 1.0 (95% CI 1.0-1.0), PM/DM κ = 0.72 (95% CI 0.49-0.95), and SS κ = 0.85 (95% CI 0.71-0.99). The screening questions had sensitivity ranging from 0.96 to 1.0 and specificity ranging from 0.88 to 1.0.

This SARD case ascertainment tool has demonstrable sensibility and validity. The use of both screening and confirmatory questions confers added accuracy.