不同实验室环境下ELISA法检测血清GM结果的可靠性研究

目的探讨半乳甘露聚糖(galactomannan，GM)检测的实验室环境影响因素以及如何降低假阳性，提高检测的准确性。方法选择2016年6月～2017年4月在南京医科大学第一附属医院初诊为疑似侵袭性真菌病的住院患者为研究对象，在不同的实验室环境下进行ELISA法检测血清GM。在一般环境下检测3　407例样本，进行随机空气培养，观察培养结果并鉴定出菌落种类，并以培养菌落制备混悬液进行处理取上清进行GM检测。在严格控制环境下检测1　167例样本，并进行两组之间的比较。〖HT5结果在一般环境下检测的真阳性率为3.38％，敏感度为63.0％(34/54)，特异度为40.9％(56/137)，阳性预测值(positive predictive value，PPV)为29.6％；在严格控制环境下真阳性率为3.94％，敏感度和特异度分别为79.4％(27/34)和34.5％(10/29)，PPV为58.7％(27/46)。两者之间，后者PPV明显高于前者，差异有统计学意义( χ2=11.85，P <0.001)。空气培养、鉴定结果及GM检测结果表明，随机污染的曲霉菌属导致较强的假阳性结果，毛霉菌属导致中度的假阳性结果，而枯草芽孢杆菌导致轻度假阳性结果。结论环境中的枯草芽孢杆菌，曲霉菌和毛霉菌对检测环境的随机污染是导致GM检测假阳性结果的重要原因，通过对检测环境严格的控制和消毒措施可以降低假阳性，改善检测结果，提高检测结果的敏感性。

Reliability Study on Serum GM Results by ELISA Methodin Different Laboratory Conditions

Objective To explore the factors in the environment that could affect the accuracy of galactomannan (GM) detection and how to reduce false-positives in order to improve accuracy．MethodsThe hospitalized patients who were initially diagnosed with suspicious invasive fungal diseases in the First Affiliated Hospital of Nanjing Medical University from June 2016 to April 2017 were selected as subjects，and serum GM was detected by enzyme-linked immunosorbent assay(ELISA) method in different laboratory environmental conditions．Detection of 3 407 samplesin were operated in normal circumstances and random air culture，observation of culture results，identification and treatment of bacterium suspension to take the supernatant for GM detection were done as well．1 167 samples were tested in strict controlled environment．Then comparisons between the two groups were performed．Results The true positive rate was 3.38% in the general environment，the sensitivity was 63.0% (34/54)，while the specificity was 40.9% (56/137)，and the positive predictive value (PPV) was 29.6.%．The true positive rate was 3.94% in strict controlled environment，sensitivity and specificity were 79.4% (27/34) and 34.5% (10/29)，respectively，and PPV was 58.7% (27/46)．Between the two，the latter PPV was significantly higher than the former，the difference was statistically significant ( χ2=11.85，P <0.001)．Air culture and microorganism identification showed that random contamination by Aspergillus spp contributed to strong false-positive results， Mucor spp 　contributed to moderate false-positive results，and Bacillus subtilis contributed to mild false-positive results．Conclusion Random contamination of the testing environment by Bacillus subtilis，Aspergillus spp and Mucor spp is an important cause of false-positive results in GM detection which can be improved by using disinfected and sterilized testing environment．