Systemic immune-inflammation index combined with ferritin can serve as a reliable assessment score for adult-onset Still's disease.

Laboratory inflammatory scores can be used as a practical tool for diagnosing AOSD. The SII and ferritin combination proved to be the most powerful assessment tool. Key Points • The systemic immune-inflammation index (SII), C-reactive protein/albumin ratio (CAR), ferritin/erythrocyte sedimentation rate ratio (FER), prognostic nutritional index (PNI), and albumin/globulin ratio (AGR) can be used as initial assessment scores for AOSD. • SII combined with ferritin (AUC = 0.904; 95% CI, 0.863-0.945) appears to be the most effective and valuable assessment score for AOSD.