血清降钙素原对凝固酶阴性葡萄球菌血流感染鉴别诊断的价值

Serum procalcitonin for differential diagnosis of blood stream infections caused by coagulase-negative Staphylococcus

目的探讨降钙素原(PCT)定量检测在鉴别诊断凝固酶阴性葡萄球菌(CNS)血流感染中的临床应用价值。方法采用回顾性研究方法,收集2010年7月—2012年1月南昌大学第一附属医院血培养结果为CNS的患者73例,分为血流感染组(n=47)和血培养污染组(n=26),测定各组患者的血清PCT及C反应蛋白(CRP)浓度,比较血流感染患者与血培养污染患者PCT浓度的差异及与CRP之间的相关性,以SPSS 17.0软件进行受试者工作特征(ROC)曲线分析,计算各曲线下面积(AUC),获得最佳诊断点。结果血流感染组患者PCT浓度为8.56(2.91～23.53)μg/L,阳性率高达91.4%,而血培养污染组患者PCT浓度为0.19(0.05～0.74)μg/L,阳性率仅42.3%,差异有统计学意义(Z=-5.17,P=0.000)。两组PCT和CRP的AUC分别为0.864和0.630,以PCT=0.435μg/L为截点,PCT鉴别诊断的灵敏度为93.6%、特异度为73.2%,阳性预测值和阴性预测值分别为81.5%、84.2%。表皮葡萄球菌和人葡萄球菌人亚种引起血流感染患者PCT浓度显著高于血培养污染患者(Z=-4.117,P=0.000;Z=-2.317,P=0.020),而溶血葡萄球菌引起的血流感染患者PCT浓度与血培养污染患者之间差异无统计学意义(Z=-1.363,P=0.173)。结论 PCT可有效鉴别诊断CNS引起的血流感染和血培养污染,不同种类CNS引起的血流感染PCT浓度也存在差异。

Objective To investigate the role of serum procalcitonin （PCT） in differential diagnosis of blood stream infections （BSIs） caused by coagulase negative Staphylococcus （CNS）. Methods In a retrospective study, 73 patients with blood stream infections caused by coagulase-negative Staphylococcus were enrolled from the First Affiliated Hospital of Nanchang University during the period from July 2010 to January 2012. For this analysis, the patients were assigned to two groups： BSI or blood contamination. PCT and C-reactive protein （CRP） were measured. We compared the difference of PCT between BSI group and blood culture contamination group and its relation to CRP. The receiver operating characteristic （ROC） curves were constructed for PCT and CRP using SPSS 17.0 software. The predictors or probabilities were applied to establish the empirical and binominal model of the ROC curves to compare the area under the curve （AUC）. Results Mean PCT levels in the patients with BSI or blood culture contamination were 8.56 （2.91-23.53） μg/L and 0. 19 （0. 05-0. 74）μg/L, while the PCT positive rate was 91.4% and 42.3%, respectively. The difference between these groups was statistically significant （Z = - 5.17, P = 0. 000）. The AUC of PCT and CRP was 0. 864 and 0. 630, respectively. ROC analysis revealed that optimal discrimination between BSI and blood culture contamination at a suggested cut-off point of 0. 435μg/L with a sensitivity of 93.6% and specificity of 73.2%. The corresponding positive and negative predictive value was 81.5% and 84.2%, respectively. The PCT level in the patients with BSI caused by Staphylococcus epidermidis and Staphylococcus hominis was higher than that in the patients with blood culture contamination （Z = - 4.117 and - 2.317, all P〈0.05）. The PCT level in the patients with BSI caused by Staphylococcus haemolyticus was higher than that in the patients with blood culture contamination （Z = - 1. 363, P TM 0. 173）. Conclusions PCT is a more useful parameter for differen tiating BSI from blood culture contamination than other markers such as CRP. The PCT concentration is different significantly among the patients with BSIs caused by different coagulase-negative Staphylococcus.