Service of Infectious Diseases, Cardarelli Hospital, Naples, Italy.
Department of Infectious Diseases, D. Cotugno Hospital, AORN dei Colli - Naples.
Clin Orthop Relat Res. 2021 Sep 1;479(9):2061-2068. doi: 10.1097/CORR.0000000000001788.
Although synovial fluid can be used to diagnose periprosthetic joint infections (PJI) effectively, only the cutoff values adopted at the time of PJI diagnosis have been standardized, and few data are currently available about effectiveness of synovial fluid examination before definitive reimplantation.
QUESTIONS/PURPOSES: We asked: (1) What are the most appropriate thresholds for synovial fluid leukocyte counts (WBC) and neutrophil percentage (PMN percentage) in a patient group undergoing definitive reimplantation after an uninterrupted course of antibiotic therapy for chronic PJI? (2) What is the predictive value of our synovial WBC and PMN percentage threshold compared with previously proposed thresholds?
In all, 101 patients with PJI were evaluated for inclusion from January 2016 to December 2018. Nineteen percent (19 of 101) of patients were excluded because of the presence of a chronic inflammatory disease, acute/late hematogenous infection, low amount of synovial fluid for laboratory investigations or infection persistence after spacer placement, and adequate antibiotic therapy. Finally, 81% (82 of 101) of patients with a median (range) age of 74 years (48 to 92) undergoing two-stage revision for chronic TKA infection, who were followed up at our institution for a period 96 weeks or more, were included in this study. The patients did not discontinue antibiotic treatment before reimplantation and were treated for 15 days after reimplantation if intraoperative cultures were negative. No patient remained on suppressive treatment after reimplantation. Synovial fluid was aspirated aseptically with a knee spacer in place to evaluate the cell counts before reimplantation. Thirteen percent (11 of 82) of patients had persistent or recurrent infection, defined as continually elevated erythrocyte sedimentation rate or C-reactive protein levels coupled with local signs and symptoms or positive cultures. The synovial fluid WBC counts and PMN percentage from the 11 patients with persistent or recurrent PJI were compared with the 71 patients who were believed to be free of PJI. Receiver operating characteristic (ROC) curve analyses assessed the predictive value of the parameters, and the areas under the curves (AUCs) were evaluated. The sensitivities, specificities, and positive and negative predictive values were determined for the WBC count and PMN percentage. Patients with persistent or recurrent infection had higher median WBC counts (471 cells/µL versus 1344 cells/µL; p < 0.001) and PMN percentage (36% versus 61%; p < 0.001) than did patients believed to be free of PJI.
ROC curve analysis identified the best threshold values to be a WBC count of 934 cells/µL or more (sensitivity 0.82 [95% CI 0.71 to 0.89], specificity 0.82 [95% CI 0.71 to 0.89]) as well as a PMN percentage of at least 52% (sensitivity 0.82 [95% CI 0.71 to 0.89] and specificity 0.78 [95% CI 0.67 to 0.86]. We found no difference between the AUCs for the WBC count and the PMN percentage (0.87 [95% CI 0.79 to 0.96] versus 0.84 [95% CI 0.73 to 0.95]. Comparing the sensitivities and specificities of the synovial fluid WBC count and PMN percentage proposed by other authors, we find that a PMN percentage more than 52% showed better predictive value than previously reported.
Based on our findings, we believe that patients with WBC counts of at least 934 and PMN percentage of 52% or more should not undergo reimplantation but rather a repeat debridement, as their risk of persistent or recurrent PJI appears prohibitively high. The accuracy of the proposed cutoffs is better than previously reported.
Level III, diagnostic study.
尽管滑液可有效用于诊断假体周围关节感染（PJI），但目前仅标准化了 PJI 诊断时采用的截止值，而关于明确再植入前滑液检查的有效性的数据很少。
问题/目的：我们提出了以下问题：（1）在不间断接受抗生素治疗慢性 PJI 后进行明确再植入的患者群体中，滑液白细胞计数（WBC）和中性粒细胞百分比（PMN%）的最佳阈值是什么？（2）与先前提出的阈值相比，我们的滑液 WBC 和 PMN%阈值的预测价值如何？
2016 年 1 月至 2018 年 12 月，共评估了 101 例 PJI 患者，其中 19%（19/101）因慢性炎症性疾病、急性/晚期血源性感染、滑液量少或感染在放置间隔器后持续存在、以及抗生素治疗有效而被排除。最终，纳入了 81%（82/101）名年龄中位数（范围）为 74 岁（48-92 岁）的接受二期翻修慢性 TKA 感染的患者，这些患者在我院随访至少 96 周，这些患者在再植入前未停止抗生素治疗，并且在再植入后如果术中培养物为阴性则治疗 15 天。再植入后，没有患者继续接受抑制性治疗。在再植入前，使用膝关节间隔器无菌抽吸滑液，以评估再植入前的细胞计数。13%（11/82）的患者发生持续或复发性感染，定义为持续升高的红细胞沉降率或 C 反应蛋白水平，同时伴有局部体征和症状或阳性培养物。将 11 例持续或复发性 PJI 患者的滑液 WBC 计数和 PMN%与 71 例认为无 PJI 的患者进行比较。接受者操作特征（ROC）曲线分析评估了参数的预测价值，并评估了曲线下面积（AUCs）。确定了 WBC 计数和 PMN%的敏感性、特异性、阳性和阴性预测值。与认为无 PJI 的患者相比，持续或复发性感染患者的中位 WBC 计数（471 个/µL 比 1344 个/µL；p<0.001）和 PMN%（36%比 61%；p<0.001）更高。
ROC 曲线分析确定了最佳阈值为 WBC 计数≥934 个/µL（敏感性 0.82 [95%CI 0.71 至 0.89]，特异性 0.82 [95%CI 0.71 至 0.89]）以及 PMN%≥52%（敏感性 0.82 [95%CI 0.71 至 0.89]和特异性 0.78 [95%CI 0.67 至 0.86]。我们发现 WBC 计数和 PMN%的 AUC 之间没有差异（0.87 [95%CI 0.79 至 0.96] 比 0.84 [95%CI 0.73 至 0.95]）。比较其他作者提出的滑液 WBC 计数和 PMN%的敏感性和特异性，我们发现 PMN%超过 52%具有更好的预测价值。
根据我们的发现，我们认为 WBC 计数至少为 934 个/µL 且 PMN%为 52%或更高的患者不应进行再植入，而应再次清创，因为他们发生持续或复发性 PJI 的风险似乎高得令人望而却步。所提出的截止值的准确性优于先前报道。
III 级，诊断研究。
