Diagnosis of periprosthetic joint infections in patients who have rheumatoid arthritis: application of routine serological and synovial fluid indexes

• Published in: Bone & joint research 2023-09, Vol.12 (9), p.559-570
• Main Authors: Wang, Yulai, Li, Guoqing, Ji, Baochao, Xu, Boyong, Zhang, Xiaogang, Maimaitiyiming, Asihaerjiang, Cao, Li
• Format: Article
• Language: English
• Subjects: crp; diagnosis; diagnostic test; Infection; knees; osteoarthritis (oa); periprosthetic joint infection; periprosthetic joint infection (pji); rheumatoid arthritis; serology; synovial fluid; total hip arthroplasty (tha); total knee arthroplasty; white blood cells
• ISSN: 2046-3758; 2046-3758
• DOI: 10.1302/2046-3758.129.BJR-2022-0432.R1

Aims: To investigate the optimal thresholds and diagnostic efficacy of commonly used serological and synovial fluid detection indexes for diagnosing periprosthetic joint infection (PJI) in patients who have rheumatoid arthritis (RA). Methods: The data from 348 patients who had RA or osteoarthritis (OA) and had previously undergone a total knee (TKA) and/or a total hip arthroplasty (THA) (including RA-PJI: 60 cases, RA-non-PJI: 80 cases; OA-PJI: 104 cases, OA-non-PJI: 104 cases) were retrospectively analyzed. A receiver operating characteristic curve was used to determine the optimal thresholds of the CRP, ESR, synovial fluid white blood cell count (WBC), and polymorphonuclear neutrophil percentage (PMN%) for diagnosing RA-PJI and OA-PJI. The diagnostic efficacy was evaluated by comparing the area under the curve (AUC) of each index and applying the results of the combined index diagnostic test. Results: For PJI prediction, the results of serological and synovial fluid indexes were different between the RA-PJI and OA-PJI groups. The optimal cutoff value of CRP for diagnosing RA-PJI was 12.5 mg/l, ESR was 39 mm/hour, synovial fluid WBC was 3,654/μl, and PMN% was 65.9%; and those of OA-PJI were 8.2 mg/l, 31 mm/hour, 2,673/μl, and 62.0%, respectively. In the RA-PJI group, the specificity (94.4%), positive predictive value (97.1%), and AUC (0.916) of synovial fluid WBC were higher than those of the other indexes. The optimal cutoff values of synovial fluid WBC and PMN% for diagnosing RA-PJI after THA were significantly higher than those of TKA. The specificity and positive predictive value of the combined index were 100%. Conclusion: Serum inflammatory and synovial fluid indexes can be used for diagnosing RA-PJI, for which synovial fluid WBC is the best detection index. Combining multiple detection indexes can provide a reference basis for the early and accurate diagnosis of RA-PJI. Cite this article: Bone Joint Res 2023;12(9):559–570.