初次膝关节穿刺后培养结果假阳性：是真是假。
False-positive Cultures After Native Knee Aspiration: True or False.
作者信息
Jennings Jason M, Dennis Douglas A, Kim Raymond H, Miner Todd M, Yang Charlie C, McNabb David C
机构信息
Colorado Joint Replacement, 2535 S Downing Street, Suite 100, Denver, CO, 80210, USA.
Department of Biomedical Engineering, University of Denver, Denver, CO, USA.
出版信息
Clin Orthop Relat Res. 2017 Jul;475(7):1840-1843. doi: 10.1007/s11999-016-5194-4.
BACKGROUND
Synovial fluid aspiration is a routine practice used by most orthopaedic surgeons to aid in the diagnosis of joint infection. In patients for whom there is a low pretest probability of infection, a positive culture-particularly if it is a broth-only culture-may be considered a contaminant, especially if the bacterial species are skin pathogens. To our knowledge no study has evaluated the incidence of contamination of aspirations from the native knee.
QUESTIONS/PURPOSES: What is the frequency of false-positive cultures among knee aspirations of the native knee?
METHODS
Two hundred patients, with a total of 200 knees, with the diagnosis of degenerative osteoarthritis undergoing a total knee arthroplasty (TKA) were identified for this study. None of these patients had symptoms, signs, or laboratory studies to suggest the presence of joint infection; a positive culture in this population therefore would be considered contaminated. Thirty-two (16%) patients were excluded secondary to a dry aspiration. One patient was enrolled in the study but did not have the knee aspirated and another patient's specimen was accidentally discarded. Each knee was aspirated under sterile conditions before performing the TKA. The fluid was sent for cell count and culture. If insufficient fluid was obtained for both cell count and culture, culture was performed rather than cell count.
RESULTS
There were no false-positive cultures (zero of 166 [0%]) in aspirations of native knees.
CONCLUSIONS
Our study would indicate that when done properly under sterile technique, cultures taken from knee arthrocentesis in patients without prosthetic joints should not be affected by perceived contaminant species. A positive specimen finding on culture should raise a strong suspicion of bacterial septic arthritis. Future studies should include more specimens as well as knees with prior TKA to help further identify the rate of false-positive cultures in knee arthrocentesis in both populations.
LEVEL OF EVIDENCE
Level I, diagnostic study.
背景
关节液抽吸是大多数骨科医生用于辅助诊断关节感染的常规操作。对于感染预测试概率较低的患者，培养结果呈阳性——尤其是仅肉汤培养阳性——可能被视为污染物，特别是如果细菌种类为皮肤病原体。据我们所知，尚无研究评估天然膝关节穿刺液污染的发生率。
问题/目的：天然膝关节穿刺培养假阳性的频率是多少？
方法
本研究纳入200例诊断为退行性骨关节炎且计划行全膝关节置换术（TKA）的患者，共200个膝关节。这些患者均无提示关节感染的症状、体征或实验室检查结果；因此，该人群中培养结果呈阳性将被视为污染。32例（16%）患者因穿刺未抽出液体而被排除。1例患者纳入研究但未进行膝关节穿刺，另1例患者的标本意外丢弃。在进行TKA之前，每个膝关节均在无菌条件下进行穿刺。将液体送去进行细胞计数和培养。如果获得的液体不足以同时进行细胞计数和培养，则进行培养而非细胞计数。
结果
天然膝关节穿刺培养均无假阳性结果（166例中0例[0%]）。
结论
我们的研究表明，在无菌技术下正确操作时，无人工关节患者膝关节穿刺培养不应受所谓污染菌种类的影响。培养发现阳性标本应高度怀疑细菌性化脓性关节炎。未来的研究应纳入更多标本以及既往行TKA的膝关节，以进一步明确这两类人群膝关节穿刺培养假阳性率。
证据水平
I级，诊断性研究。
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