Reliability and Construct Validity of the Physician's Global Assessment of Lung Disease in Systemic Juvenile Idiopathic Arthritis–Associated Lung Disease

Objective: The physician global assessment of lung disease (PGALD) is a recently proposed disease activity measure for patients with systemic juvenile idiopathic arthritis–associated lung disease (SJIA-LD). This study evaluates the reliability and construct validity of the PGALD. Methods: Fifty-seven pediatric rheumatologists and pulmonologists with experience caring for children with SJIA-LD were invited to rate 20 clinical vignettes using the PGALD, a 10-point Likert scale (0 = inactive SJIA-LD; 10 = highly active SJIA-LD). Raters were also asked to rate a subset of eight repeat vignettes. Interrater and intrarater reliability were assessed using intraclass correlation coefficients (ICCs), whereas SJIA-LD features influencing PGALD ratings were assessed using univariate analysis. Results: The ICC for all raters was 0.68 (95% confidence interval [CI] 0.54–0.82), indicating moderate to good interrater reliability. The retest ICC was 0.86 (95% CI 0.82–0.89), indicating good intrarater reliability. Factors associated with higher mean PGALD scores included the presence of crackles on auscultation (5.7 vs 2.9; P = 0.001), hypoxemia on pulse oximeter (5.6 vs 3.2; P = 0.01), current oxygen requirement (6.3 vs 3.5; P = 0.04), suggestive diagnostic imaging features (P ≤ 0.01), and three or more prescribed medications for SJIA-LD (P ≤ 0.01). Pulmonary function measures demonstrated significant negative correlations with PGALD scores: forced vital capacity (r = −0.71; P = 0.01), total lung capacity (r = −0.92; P = 0.01), and lung diffusion capacity (r = −0.97; P = 0.0002). Only C-reactive protein was weakly to moderately correlated with PGALD scores (r = 0.39; P = 0.09), whereas other laboratory markers (ferritin, interleukin 18, CXCL9, and sIL-2R) were not significantly correlated. Conclusions: The PGALD is a novel measure of SJIA-LD activity. Its initial validation suggests acceptable construct validity and reliability. Additional studies are needed to assess its responsiveness to change over time.