Abstract: OBJECTIV To observe the significance of change of procalcitonin (PCT) level in rheumatoid arthritis patients with early infections after artificial joint replacement so as to control the early infections, block the evolution of disease, and reduce the incidence of complications. METHODS From Feb 2012 to Mar 2016, totally 20 rheumatoid arthritis patients who had infections after artificial joint replacement were chosen as the infection group, 222 patients who did not have infection were assigned as the non-infection group, and 48 healthy people who received physical examination were set as the control group. The erythrocyte sedimentation rate (ESR), white blood cell (WBC) counts, C-reactive protein (CRP), and PCT were observed and compared before the surgery and after the surgery for 48 hours. RESULTS The ESR level was (31.10±7.90) mm/h in the infection group before the surgery, (33.00±4.00)mm/h in the non-infection group, higher than (19.50±3.00) mm/h in the control group; the CRP level was (8.20±2.01) mg/L in the infection group before the surgery , (8.00±1.30) mg/L in the non-infection group, higher than (5.34±2.20) mg/L in the control group, and there was significant difference (P<0.05). The PCT level was (0.31±0.11) ng/mL in the infection group, (0.33±0.12) ng/mL in the non-infection group, (0.24±0.15) ng/mL in the control group; the WBC level was (9.50±3.04) ×10⁹/L in the infection group, (9.62±3.44) ×10⁹/L in the non-infection group, (8.23±1.21) ×10⁹/L in the control group, and there was no significant difference. The levels of ESR, PCT, CRP, and WBC were respectively (69.04±9.80) mm/h, (12.60±1.96) ng/mL, (23.08±6.87) mg/L, and (18.63±4.98) ×109/L in the infection group after the surgery for 48 hours and were respectively (42.13±11.30) mm/h, (5.54±3.17) ng/mL, (12.20±3.56) mg/L, and (11.98±2.15) ×10⁹/L in the non-infection group, higher than those before the surgery, and there was significant difference (P<0.05). The levels of ESR, PCT, CRP, and WBC of the infection group were higher than those of the control group after the surgery for 48 hours, and there was significant difference (P<0.05). The sensitivity of the ESR level was 89.58%, the sensitivity of PCT was 91.67%, higher than 79.17% of the CRP and 60.42% of the WBC; the specificity of the PCT level was 89.18%, the positive predictive value of the PCT was 67.69%, higher than that of the ESR, CRP, and WBC; the area under ROC curve of the PCT was 0.872, the cutoff value 10.50 ng/mL. CONCLUSION The change of the PCT level may facilitate the diagnosis of the early infection in the rheumatoid arthritis patients after artificial joint replacement; the cutoff value of the PCT is 10.50 ng/mL, which may provide guidance for early clinical diagnosis.