Interleukin-6 and its relationship to C-reactive protein and fever in children with febrile neutropenia.

The assessment of febrile neutropenia is problematic. C-reactive protein (CRP) values alone do not differentiate those patients with microbiologically documented infections from those with unexplained fevers. Plasma interleukin-6 (IL-6), measured by ELISA, was correlated with different diagnostic groups in 47 episodes of febrile neutropenia in children. Samples were collected daily from admission until resolution of fever. On admission, the median IL-6 value for gram-negative infections was 1610 pg/ml (range, 896-40,000), for gram-positive infections it was 138 pg/ml (range, 66-1045), and for unexplained fevers it was 50 pg/ml (range, 24-135, with a single high value of 665 pg/ml). These medians were significantly different (P less than .005). There was no significant difference in median CRP values. IL-6 values peaked 24-48 h before CRP values. There was a positive correlation of IL-6 with the presence of fever. Plasma IL-6 may be a more sensitive marker than CRP of acute infection and should prove useful in the assessment of fevers in these patients.