A research found PCT, at 0.4 ng/ml, was 85.2% sensitive and 87.3% specific in diagnosing septic arthritis and acute osteomyelitis; However, in comparison, PCT at conventional cut-off of 0.5 ng/ml is 66.7% sensitive and 91% specific, it seemed 0.4 ng/ml more suitable for diagnosis osteomyelitis [7]. This evidence concerns the gene CALCA and bacterial arthritis.