CLINICAL STUDY ON THE EARLY DIFFERENTIAL DIAGNOSIS OF INFECTION IN PATIENTS WITH FEVER IN OUTPATIENT AND EMERGENCY DEPARTMENT BY COMBINED DETECTION OF SAA, CRP, IL-6 AND PCT

Teng Wang¹, Ping Zheng¹, Qian Jiang¹, Qianqian Sun^2*

¹Department of Pediatrics, Chengyang People’s Hospital, Qingdao 266109, Shandong, China - ²Department of Pediatrics, Binzhou Medical University Hospital, Qingdao 256603, Shandong, China

Objective: To investigate the diagnostic value of serum amyloid A (SAA), C-reactive protein (CRP), interleukin-6 (IL-6) and procalcitonin (PCT) in the early stage of infection in patients with fever. 

Methods: 112 cases of febrile patients who were hospitalized in our hospital from September 2018 to September 2019 were divided into bacterial group (n=60) and viral group (n=52) according to the causes of the disease. 30 healthy patients who were examined in the physical examination centre of our hospital were selected as the control group at the same time. 5ml of fasting venous blood was collected from all the subjects, and the serum SAA level was detected by immunonephelometry. The serum levels of PCT, CRP and IL-6 were detected by fluorescence immunoassay. ELISA, Pearson linear correlation analysis, ROC curve analysis, SAA, CRP, IL-6 and PCT were used in the differential diagnosis of febrile patients in the early stage of infection. 

Results: The serum levels of SAA, CRP, IL-6 and PCT in the virus group and bacteria group were significantly higher than those in the control group, and the serum levels of SAA, CRP, IL-6 and PCT in the bacteria group were significantly higher than those in the virus group (P<0.05). The positive rates of SAA, CRP, IL-6 and PCT in the bacterial group were significantly higher than those in viral group (P<0.05). There was a positive correlation between SAA, CRP, IL-6 and PCT in the bacterial group and no significant correlation between SAA, CRP, IL-6 and PCT in the viral group (P>0.05). ROC curve analysis showed that the AUC of SAA was 0.725 in the early stage of bacterial infection of STBI, the best cut-off value was 332.05mg/l, the sensitivity of this point was 71.15% and the specificity was 72.48%. AUC of CRP in the early stage of bacterial infection was 0.658, the best cut-off value was 52.16 and the sensitivity and specificity of mg / L were 63.14% and 67.94% respectively. AUC of IL-6 was 0.762 and the best cut-off value was 98.26 ng/ml, 73.15% and 75.25% respectively. AUC of PCT was 0.712 and the best cut-off value was 2.15% respectively. The sensitivity and specificity of ng/L were 70.15% and 71.26% respectively, and the AUC of the early stage of bacterial infection was 0.856, 86.26% and 82.33% respectively. 

Conclusion: SAA, CRP, IL-6 and PCT are highly expressed in the serum of patients with early bacterial infection, which has a certain value in the diagnosis of early bacterial infection, and the value of combined diagnosis is the highest.