CRP and macrophage activation syndrome: The highest risk of MAS was estimated for patients simultaneously characterized by age ≥ 45 years, ferritin ≥ 4,178.10 ng/mL, CRP ≥ 27.15 mg/L, and a systemic score ≥ 7, corresponding to a 34.7% probability of MAS, as well as for those characterized by ferritin ≥ 4,178.10 ng/mL, CRP ≥ 27.15 mg/L, and systemic score ≥ 7, corresponding to a 33.5% probability of MAS.<h4>Conclusions</h4>A machine-learning-driven prediction of MAS was explored in Still's disease, highlighting the importance of age of onset, hyperferritinaemia, increased CRP, and multiorgan involvement.