Medical Research Council, Respiratory and Meningeal Pathogens Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Division of Infectious Diseases and Hospital Epidemiology, Kantonsspital St. Gallen, St. Gallen, Switzerland
Medical Research Council, Respiratory and Meningeal Pathogens Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa Department of Science and Technology/National Research Foundation, Vaccine Preventable Diseases, University of the Witwatersrand, Johannesburg, South Africa.
J Clin Microbiol. 2014 Dec;52(12):4224-9. doi: 10.1128/JCM.01553-14. Epub 2014 Sep 24.
Quantitative lytA real-time PCR (rtPCR) results from nasopharyngeal (NP) swabs distinguish community-acquired pneumococcal pneumonia (CAP) from asymptomatic colonization. The use of an optimized cutoff value improved pneumococcal etiology determination compared to that of traditional diagnostic methods. Here, we compare the utility of lytA rtPCR from induced sputum and from NP swabs. Pneumococcus was considered the cause of CAP in HIV-infected South African adults if blood culture, induced-sputum culture or Gram stain, urine antigen test, or whole-blood lytA rtPCR revealed pneumococcus or if lytA rtPCR from NP swabs gave a result of >8,000 copies/ml. lytA rtPCR was also performed on induced sputum. Pneumococcus was detected by lytA rtPCR from sputum in 149 (67.1%) of 222 patients with available induced sputum, whereas the results of either Gram stain or culture of sputum were positive in 105 of 229 patients (45.9%; P < 0.001). The mean copy numbers from sputum were higher when the sputum cultures were positive than when the sputum cultures were negative (7.9 versus 5.6 log10 copies/ml; P < 0.001). Against the composite diagnostic standard, a cutoff value of 10,000 copies/ml for good-quality sputum lytA rtPCR had a sensitivity of 78.1% and a specificity of 80.0%. This cutoff value performed similarly to the previously identified cutoff value of 8,000 copies/ml for NP swab lytA rtPCR (area under the curve receiver operating characteristic [AUC-ROC], 80.4% for sputum of any quality versus 79.6% for NP swabs). The AUC-ROC for good-quality sputum was 83.2%. Overall, lytA rtPCR performs similarly well on induced sputum as on NP swabs for most patients but performs slightly better if good-quality sputum can be obtained. Due to the ease of specimen collection, NP swabs may be preferable for the diagnosis of pneumococcal pneumonia.
定量 lytA 实时 PCR（rtPCR）结果来自鼻咽（NP）拭子可区分社区获得性肺炎（CAP）与无症状定植。与传统诊断方法相比，使用优化的截止值可提高肺炎球菌病因的确定。在这里，我们比较诱导痰和 NP 拭子中 lytA rtPCR 的效用。如果血培养、诱导痰培养或革兰氏染色、尿抗原检测或全血 lytA rtPCR 显示肺炎球菌，或 NP 拭子的 lytA rtPCR 结果>8000 拷贝/ml，则认为 HIV 感染的南非成年人中的 CAP 由肺炎球菌引起。也对诱导痰进行了 lytA rtPCR。在 222 名有可用诱导痰的患者中，149 名（67.1%）患者的痰中通过 lytA rtPCR 检测到肺炎球菌，而 229 名患者中有 105 名（45.9%）患者的痰革兰氏染色或培养阳性（P<0.001）。与复合诊断标准相比，当痰培养阳性时，痰中的平均拷贝数高于当痰培养阴性时（7.9 与 5.6 log10 拷贝/ml；P<0.001）。对于良好质量的痰 lytA rtPCR，10,000 拷贝/ml 的截止值对复合诊断标准的敏感性为 78.1%，特异性为 80.0%。该截止值与之前确定的 NP 拭子 lytA rtPCR 8,000 拷贝/ml 的截止值（任何质量的痰的曲线下面积接收器操作特征[AUROC]为 80.4%，而 NP 拭子为 79.6%）表现相似。良好质量的痰的 AUROC 为 83.2%。总体而言，对于大多数患者，诱导痰中的 lytA rtPCR 与 NP 拭子的表现相似，但如果能获得高质量的痰，其性能会稍好一些。由于标本采集容易，NP 拭子可能更适合肺炎球菌肺炎的诊断。
