Question 问题：

Procalcitonin can help differentiate viral from bacterial pathogens in patients admitted for Community Acquired Pneumonia. Typical bacteria result in higher PCT levels than atypical bacteria or viruses. Why? How reliable is PCT testing for CAP? 

降钙素原（PCT）有助于鉴别社区获得性肺炎（CAP）是病毒性还是细菌性的。典型细菌感染PCT高于非典型细菌或病毒。为什么？PCT试验在CAP中可靠吗？

Answer 答案：

Cytokines, associated with bacterial infections, enhance PCT release, while interferons, associated with viral infections, inhibit PCT release. However, PCT will not be elevated in up to 23% of typical bacterial infections. 

与细菌感染相关的细胞因子增加PCT释放，而与病毒相关感染却抑制PCT释放。但是，PCT在23%典型细菌感染中并不升高。

参考文献：

CCJM. Vol. 87:145