Serum level of peptide LL-37 in patients with hand-foot-mouth disease caused by enterovirus 71 infection

Hand-foot-mouth disease (HFMD) is a potentially life-threatening infectious disease to children, however, its clinical diagnosis usually takes 2-3 weeks. The expression of an antimicrobial peptide LL-37 is upregulated in response to viral infection and detectable in multiple cell types, whether it could be used for HFMD diagnosis is unclear. In this study, the serum levels of LL-37 and other routine biochemical parameters, including C-reactive protein (CRP), Creatine Kinase (CK), Creatine Kinase isoenzyme (CKMB), interleukin-6 (IL-6), and white blood cell count (WBC), were detected in EV-71 associate HFMD children, which were significantly higher than in healthy controls. The cut-off value of LL-37 was < 6.04 ng/ml, with a sensitivity of 94.5%, a specificity of 69.81%, a positive predictive value of 92.8%, and a negative predictive value of 75.5%. To compare the diagnosis abilities of these parameters in HFMD children, the receiver operating characteristic curve (ROC) of LL-37, CK, CKMB, WBC, CRP and IL-6 were calculated and analyzed. Moreover, a close relationship between serum LL-37 and CKMB was found. Our results suggested that the serum LL-37 level could be used as a biochemical marker for diagnosing HFMD children infected with EV71.