A combination of WCC >11 × 109/L, neutrophil count >7× 109/L, evidence of left shift (>75% neutrophils:lymphocytes) and a CRP >5 mg/L was significant for a diagnosis of appendicitis (P < 0.001) with a specificity of 88% for the diagnosis of AA, with a positive predictive value of 80%. The gene discussed is CRP; the disease is appendicitis.