Serum procalcitonin for discrimination between septic and non-septic arthritis

Background. Early differentiation be- tween septic and non-septic arthritis is diffi cult. A previous study showed promising diagnostic accuracy of se- rum Procalcitonin (PCT) in septic ar- thritis, limited by a low sensitive PCT test kit. Objective. To investigate the diagnos- tic value of PCT in patients with septic and non-septic arthritis using a novel test with low detection limit. Methods. Forty-two patients, 28 with non-septic and 14 with septic arthritis were prospectively included. For each patient, gram stain, culture and po- larization microscopy of synovial fl uid was done and PCT, C-reactive protein (CRP), white blood cell count, uric acid and blood cultures were taken. Patients with septic arthritis, patients with non- septic arthritis with and without con- comitant infection were compared. Results. Patients with septic arthritis had a signifi cant higher PCT concen- tration than patients with non-septic arthritis (p<0.0001). At a cut-off of 0.1 (0.25) ng/ml, sensitivity for septic arthritis was 100(93)% and specifi city 46(75)%. Specifi city rose to 93% after exclusion of patients with non-septic arthritis and concomitant infection. Both sensitivity and specifi city for the diagnosis of septic arthritis were high- er for PCT than CRP. Conclusions. Our data suggest that PCT seems to be a highly sensitive and specifi c marker for septic arthritis, de- pending on the clinical setting. Further studies are warranted.