The Clinical Diagnostic Values of SAA, PCT, CRP, and IL-6 in Children with Bacterial, Viral, or Co-Infections

Background: Bacterial, viral, and bacterial and viral co-infections generally lead to inflammatory-related diseases. The aim of this study is to assess the clinical diagnostic values of serum amyloid A (SAA), procalcitonin (PCT), C-reactive protein (CRP), and interleukin (IL)-6 in children with bacterial, viral, or co-infections. Methods: A total of 181 children with infection symptoms (bacterial infection (Bac group), n = 46; viral infection (Vir group), n = 7; co-infections (Bac + Vir group), n = 128) were enrolled in our hospital from December 2019 to April 2020. Meanwhile, 42 healthy children without any infections were used as the controls. Venous blood samples were collected and the levels of serum SAA, PCT, CRP, and IL-6 were determined by immunoluminometric assay under an IMMAGE ® analyzer. The diagnostic values of these biomarkers were assessed using the receiver operating characteristic (ROC) curves. Results: The results indicated that IL-6 level was increased in three infection groups compared to the controls. Both SAA and CRP were significantly elevated in Vir and Bac + Vir groups. High level of PCT was observed in Bac and Bac + Vir goups. In addition, PCT (0.9281, 95% CI = 0.8645– 0.9916) alone is an effective method for identifying bacterial infections. SAA in combination with CRP may distinguish co-infection from bacterial infection. Simultaneous positive of SAA, PCT, IL-6, and CRP can discriminate co-infection from the healthy controls. Conclusion: In a word, the levels of serum SAA, PCT, CRP, and IL-6 are increased to varying degrees in different infection situations. Our findings may provide early diagnosis for patients with different infections. Keywords: bacterial infection, viral infection, co-infection, combined biomarkers, diagnostic accuracy