Changes in perioperative C-reactive protein levels in patients with rheumatoid arthritis undergoing total knee arthroplasty in the biologic era.

This study aimed to investigate changes in and factors associated with perioperative serum C-reactive protein (CRP) levels in rheumatoid arthritis (RA) patients undergoing total knee arthroplasty (TKA) in the biologic era. A total of 173 patients (228 knees) with RA underwent elective primary TKA at our institute between January 1, 2006 and December 31, 2018. Of these, 214 cases among 161 patients were examined in this retrospective study after excluding 3cases among 3 patients who developed postoperative complications and 11 cases among 9 patients who were treated with tocilizumab. Factors associated with changes in CRP levels between baseline (preoperative) and day 7 after TKA [ΔCRP (0-7days)] were assessed by multiple regression analysis. Median (interquartile range) CRP levels were 0.69 (0.21, 1.82) mg/dl preoperatively, 5.66 (4.21, 7.61) mg/dl on postoperative day 1, 12.75 (9.79, 16.74) mg/dl on postoperative days 3-4, 3.26 (2.21, 4.85) mg/dl on postoperative day 7, and 0.87 (0.45, 1.81) mg/dl on postoperative day 14. Multivariate regression analysis revealed that body mass index ≥25 [partial regression coefficient (B)=1.03, P=0.012] and use of glucocorticoids (B=-0.86, P=0.017) were independently associated with ΔCRP (0-7days), whereas use of methotrexate and targeted drug modifying antirheumatic drugs and preoperative CRP levels (an objective biomarker of RA activity) were not. In conclusion, serum CRP levels increased rapidly after TKA and peaked on postoperative days 3-4, followed by a return to preoperative levels by postoperative day 14 in patients with RA. Obesity and the use of glucocorticoids were independently associated with changes in CRP levels.