Serum lnterleukin-6 in differentiation between bacterial and nonbacterial acute otitis media

Background. Although acute otitis media (AOM) is generally treated with antibiotics, bacteria cannot be isolated from the middle ear effusion in about 30% of the cases. If nonbacterial etiology of AOM could be determined early In the course of the infection, antibiotic treatment might be safely withheld in these cases. We studied whether serum IL-6 levels could be used to differentiate between bacterial and nonbacterial etiology of AOM. Methods. IL-6 concentrations in stored serum samples from 184 children enrolled in AOM trials between 1989 and 1991 were determined by enzyme-linked immunoassay (RandD Systems, Minneapolis, MN). The etiology of AOM had been determined by bacterial and viral cultures as well as respiratory syncytial virus antigen detection in the middle ear fluids. Results. Children with bacterial AOM had significantly higher IL-6 levels than those with nonbacterial AOM (median, 11.5 vs. 3.7 pg/ml; P<0.001). The sensitivity and specificity of serum IL-6 for detection of bacterial AOM at the cutoff value of 10 pg/ml were 54% and 76%, and at the cutoff value of 30 pg/ml 27% and 93%, respectively. Serum IL-6 concentrations in AOM caused by S. pneumonias were significantly higher than those associated with H. influenzae or M. catanhalis, and at the cutoff value of 50 pg/ml the specificity of IL-6 for detection of pneumococcal Infection was 96%. Conclusions. Serum IL-6 levels are significantly higher in bacterial than in nonbacterial AOM, but because this difference is almost entirely attributed to S. pneumoniae, low IL-6 concentrations do not reliably rule out bacterial etiology of AOM in general. On the other hand, serum IL-6 concentrations of > 30 pg/ml are highly suggestive of pneumococcal AOM, and levels of > 50 pg/ml are almost exclusively associated with pneumococcal etiology.