Abstract: ObjectiveTo investigate the the prectical value of serum procalcitonin (PCT)/c-reactive protein (CRP) joint detection in the diagnosis of bacterial infections. MethodsVenous blood and body fluid specimens were collected from the in-patients without medical treatment after admission from April 2013 to July 2014. The PCT level was evaluated by double antibody sandwich immunochromatography and CRP was tested by the immune turbidimetry.Bacterial culture and identification were complished with automatic blood culture and microbe identifying system. The samples were divided into three groups:155 cases of Gram-,81 cases of Gram+ ,100 cases of negative bacteria infections, and 100 cases of healthy control. The receiver-operating characteristic curve (ROC) was used to assess the diagnositic value of PCT and CRP. ResultsThe PCT and CRP levels in Gram- infection group were found to be 7.5（2 .5-12.5） and 70 .5( 23.5-164.5);while those in Gram+ infection group were 2.5(2. 5-7.5)and 112 (48-176);and those in non-bacteria group were 1(1-1)and 49 .5( 16.5-115.5) compared with the levels of 0.07(0.03-0.09) and 3 ( 1-5) of PCT and CRP in healthy control.The PCT and CRP concentrations were higher in the bacteria infection than those in the control（P<0 .05）.Among them,PCT level of Gram- group increased more obviously than that of Gram+ group（P<0 .05）but no difference was noted of the CRP level between them（P>0 .05）. The AUG of PCT (0.994) was large compared with that of CRP（0.969, P<0 .05）.PCT test had advantage over CRP in sensitivity,specificity,accuracy,positive/negative predictive value, positive/ negative likelihood value and Youden index. ConclusionPCT may be used as a reliable marker in differentiation and early diagnosis of bacteria infections. Combined examination of both markers is valuable for disease monitoring and therapeutic evaluation in bacteria infections.

Key words: Procalcitonin, C-reactive, protein, Gram-positive, bacteria, Gram-negative, bacteria, Bacterial, infections