Colvin Otis C, Kransdorf Mark J, Roberts Catherine C, Chivers F Spencer, Lorans Roxanne, Beauchamp Christopher P, Schwartz Adam J
Department of Radiology, Mayo Clinic, 5777 E Mayo Boulevard, Phoenix, AZ, 85054, USA.
Skeletal Radiol. 2015 May;44(5):673-7. doi: 10.1007/s00256-015-2097-5. Epub 2015 Jan 29.
Analysis of joint fluid remains a key factor in the diagnosis of periprosthetic infection. Recent reports have shown that neutrophils in infected joint fluid release esterase, an enzyme that is a reliable marker for infection. Testing for leukocyte esterase is routinely done in the analysis of urine for the presence of urinary tract infection, by a simple "dipstick" method. We report our experience with this technique in the evaluation of patients suspected of having septic arthritis or periprosthetic joint infection (PJI) by comparing results of leukocyte esterase positivity with confirmed joint infection as defined by the American Academy of Orthopaedic Surgeons (AAOS).
We retrospectively reviewed leukocyte esterase test results performed on synovial fluid aspirated from 57 patients with prosthetic (52) and native (5) joints. Patients either presented with unexplained painful arthroplasties, routine testing of PROSTALAC (PROSthesis with Antibiotic-Loaded Acrylic Cement) orthopedic implants, or clinical suspicion of periprosthetic infection or septic arthritis. Synovial fluid was percutaneously aspirated using a standard technique. The patient age range was 31-91 years with a mean age of 69.1 years, consisting of 30 women (52.6 %) and 27 men (47.4 %). The "gold standard" for the presence or absence of infection at our institution and in the study group was based on the most recent recommendations of the AAOS. Positive culture remained the "gold standard" for native joint infection.
Of the total 57 joints aspirated and included in the study, 20 (35.1 %) were read as positive (2+) on the leukocyte test strip and 37 (64.9 %) were read as negative (negative, trace, or 1+). PJI was diagnosed in 19 patients and native joint septic arthritis was identified in one patient. Sensitivities were excellent at 100 % with no false negatives in the entire cohort. There was one false positive in the periprosthetic group yielding a specificity, positive predictive value and negative predictive value of 97, 95, and 100 %, respectively. The results for the native joints showed markedly less specificity and positive predictive value at 50 and 33 %; however, its negative predictive value remained at 100 %.
Our test results confirm that the leukocyte esterase test can accurately detect PJI and that it can be used as a part of the traditional PJI workup. In the assessment of native joints, its high negative predictive value suggests that it is a valuable tool in excluding native joint septic arthritis.
关节液分析仍是人工关节周围感染诊断的关键因素。最近的报告表明，感染关节液中的中性粒细胞会释放酯酶，该酶是感染的可靠标志物。白细胞酯酶检测在尿液分析中常用于检测尿路感染，采用简单的“试纸”法。我们报告了通过将白细胞酯酶阳性结果与美国矫形外科医师学会（AAOS）定义的确诊关节感染进行比较，在评估疑似化脓性关节炎或人工关节周围感染（PJI）患者时使用该技术的经验。
我们回顾性分析了从57例人工关节（52例）和天然关节（5例）抽取的滑液进行的白细胞酯酶检测结果。患者要么表现为不明原因的关节置换疼痛、PROSTALAC（含抗生素骨水泥假体）骨科植入物的常规检测，要么临床怀疑人工关节周围感染或化脓性关节炎。采用标准技术经皮抽取滑液。患者年龄范围为31 - 91岁，平均年龄69.1岁，其中女性30例（52.6%），男性27例（47.4%）。我们机构和研究组中感染存在与否的“金标准”基于AAOS的最新建议。阳性培养结果仍是天然关节感染的“金标准”。
在纳入研究的57个抽取关节中，20个（35.1%）在白细胞试纸检测中被判定为阳性（2 +），37个（64.9%）被判定为阴性（阴性、微量或1 +）。19例患者被诊断为PJI，1例患者被诊断为天然关节化脓性关节炎。整个队列的敏感性极佳，为100%，无假阴性。人工关节组有1例假阳性，特异性、阳性预测值和阴性预测值分别为97%、95%和100%。天然关节的结果显示特异性和阳性预测值明显较低，分别为50%和33%；然而，其阴性预测值仍为100%。
我们的检测结果证实白细胞酯酶检测可准确检测PJI，可作为传统PJI检查的一部分。在评估天然关节时，其高阴性预测值表明它是排除天然关节化脓性关节炎的有价值工具。
