Significance of interleukin-6 (IL-6) and C-reactive protein (CRP) in children and young adults with febrile neutropenia during chemotherapy for cancer: A prospective study

OBJECTIVES:: We evaluated the usefulness of interleukin-6 (IL-6) and C-reactive protein (CRP) at the onset of febrile neutropenia and 72 hours later, in identifying risk groups and assessing response to antibiotic therapy. METHODS:: All episodes of febrile neutropenia were divided in 3 study groups-microbiologically documented infection (MDI), clinically documented infection (CDI), and fever of unknown origin (FUO). Three outcome groups were defined as those responding to first-line antibiotics (R1), those responding to second-line antibiotics (R2), and those requiring antifungal therapy (RAF). Median values of IL-6 and CRP were compared between the groups. RESULTS:: There were 57 episodes of febrile neutropenia among 26 patients younger than 25 years during 1 year of study period. On day 1, median IL-6 level was significantly lower in FUO group compared with CDI+MDI groups combined (P<0.001). Rise in CRP on day 3 was highly significant to differentiate MDI group from other 2 groups (P<0.001). The CRP also increased significantly on day 3 in RAF (P<0.001) and R2 (P=0.002) groups than in R1 group. CONCLUSIONS:: Low level of IL-6 may help differentiate patients with FUO from those with documented infections. A rising CRP is indicative of serious infection.