CALCA and appendicitis: CRP: C-reactive protein, PCT: procalcitonin, LF: lactoferrin, CAA: complicated acute appendicitis, PA: perforated appendicitis, ED: emergency department, NP: neopterin, AP: appendicitis, UAA: uncomplicated appendicitis, WCC: white cell count, N/L ratio: neutrophil/lymphocyte ratio, IL-6: interleukin 6.