Elevated serum amyloid A levels are associated with rapidly progressive interstitial lung disease in dermatomyositis: a retrospective cohort study.

BACKGROUND: Prompt identification of rapidly progressive interstitial lung disease (RP-ILD) in dermatomyositis (DM) is crucial; however, reliable biomarkers remain lacking. OBJECTIVES: To evaluate the association between serum amyloid A (SAA) and RP-ILD in DM. METHODS: SAA levels were quantified via scattering turbidimetry. Spearman's correlation analyzed associations with serologic markers. Diagnostic thresholds were determined through ROC curve analysis, and independent markers associated with mortality were identified using Cox proportional hazards models. RESULTS: SAA levels were significantly higher in DM patients than in healthy controls (37.71 ± 6.93 vs 5.42 ± 0.30 mg/L; P < 0.0001) and were markedly elevated in those with RP-ILD (103.60 ± 18.02 mg/L). Elevated SAA was independently linked to RP-ILD. The combination of SAA and anti-MDA5 antibody provided the highest diagnostic accuracy (AUC = 0.950; 95% CI: 0.906-0.995). Patients with SAA >21.98 mg/L had significantly worse survival (P < 0.0001). SAA >21.98 mg/L independently implied mortality in multivariable analysis (HR = 14.12; 95% CI: 1.16-171.33; P = 0.038). LIMITATIONS: This was a retrospective, single-center cohort with a modest sample size. CONCLUSION: Elevated SAA is associated with increased frequency of RP-ILD and mortality. Combining SAA with anti-MDA5 antibody optimizes risk stratification and concurrent disease severity evaluation.