背景:在肺炎的情况下,一些生物学发现提示军团病(LD),包括C反应蛋白(CRP)。低水平的CRP预测军团菌尿抗原测试(L-UAT)阴性。
方法:在贝桑松大学医院进行外部验证的Nord-Franche-Comté医院的观察性回顾性研究,法国包括2018年1月至2022年12月期间所有患有L-UAT的成年人。目的是确定CRP最佳阈值以预测L-UAT阴性结果。
结果:URINELLA包括5051例患者(83例L-UAT阳性)。CRP最佳阈值为131.9mg/L,阴性预测值(NPV)为100%,敏感性为100%,特异性为58.0%。ROC曲线的AUC为88.7%(95%CI,86.3-91.1)。Besançon医院患者的外部验证显示AUC为89.8%(95%CI,85.5-94.1)和NPV,敏感性和特异性分别为99.9%,CRP阈值为131.9mg/L的97.6%和59.1%;排除免疫抑制患者后,指数敏感性和净现值也达到100%。
结论:在怀疑肺炎的情况下,CRP水平低于130mg/L(与严重程度无关),L-UAT在NPV为100%的免疫活性患者中无效。对于CRP给药前48小时内出现症状的患者,我们必须保持谨慎。
BACKGROUND: In case of pneumonia, some biological findings are suggestive for Legionnaire\'s disease (LD) including C-reactive protein (CRP). A low level of CRP is predictive for negative Legionella Urinary-Antigen-Test (L-UAT).
METHODS: Observational retrospective study in Nord-Franche-Comté Hospital with external validation in Besançon University Hospital, France which included all adults with L-UAT performed during January 2018 to December 2022. The objective was to determine CRP optimal threshold to predict a L-UAT negative result.
RESULTS: URINELLA included 5051 patients (83 with positive L-UAT). CRP optimal threshold was 131.9 mg/L, with a negative predictive value (NPV) at 100%, sensitivity at 100% and specificity at 58.0%. The AUC of the ROC-Curve was at 88.7% (95% CI, 86.3-91.1). External validation in Besançon Hospital patients showed an AUC at 89.8% (95% CI, 85.5-94.1) and NPV, sensitivity and specificity was respectively 99.9%, 97.6% and 59.1% for a CRP threshold at 131.9 mg/L; after exclusion of immunosuppressed patients, index sensitivity and NPV reached also 100%.
CONCLUSIONS: In case of pneumonia suspicion with a CRP level under 130 mg/L (independently of the severity) L-UAT is useless in immunocompetent patients with a NPV at 100%. We must remain cautious in patients with symptoms onset less than 48 h before CRP dosage.