SERUM INTERLEUKIN-6 IN BACTERIAL AND NONBACTERIAL ACUTE OTITIS-MEDIA

Background. Increasing prevalence of antibiotic-resistant bacteria is a serious clinical problem that calls for reduction of unnecessary use of antibiotics. Acute otitis media (AOM) is the most common reason fo r antibiotic therapy in the United States. Approximately 30% of AOM ea ses do not have a bacterial etiology. Rapid identification of these ca ses could help withhold unnecessary antibiotic treatment. Objective. T o determine the usefulness of serum levels of interleukin-6 (IL-6), an acute phase cytokine shown to be a reliable marker of neonatal bacter ial infection, in differentiation between bacterial and nonbacterial A OM in children. Study Design. IL-6 was measured in stored serum sample s from 184 children (mean age, 22 months) with AOM who were enrolled i n antibiotic efficacy trials at our department. The samples were obtai ned at enrollment and at 9 to 12 days after initiation of antibiotic t herapy. Sera from 21 uninfected children (mean age, 23 months) were us ed as controls. The etiology of AOM was determined by bacterial and vi ral cultures as well as respiratory syncytial virus antigen detection in the middle ear fluids obtained by tympanocentesis. Results. Bacteri al etiology of AOM was confirmed in 125 children (68%), whereas in 59 children (32%) no bacterial pathogen could be detected in the middle e ar fluid. Children with bacterial AOM had significantly higher IL-6 le vels than those with nonbacterial AOM (median, 11.5 vs 3.7 pg/mL). How ever, this difference was almost entirely attributable to pneumococcal AOM specifically. IL-6 levels in children with AOM caused by Streptoc occus pneumoniae were significantly higher (median, 40.1 pg/mL) than i n AOM caused by Haemophilus influenzae (7.3 pg/mL) or Moraxella catarr halis (6.8 pg/mL). At the cutoff value of 30 pg/mL, the specificity of IL-6 for detection of pneumococcal AOM was 91% with a sensitivity of 61%, but its sensitivity for detection of bacterial AOM in general was only 27%. Conclusions. Low levels of IL-6 do not rule out bacterial e tiology of AOM in general; therefore, IL-6 is not sensitive enough as a marker of bacterial AOM. Surprisingly, serum IL-6 levels in pneumoco ccal AOM were significantly higher than the levels associated with oth er bacterial AOM, and serum IL-6 levels of >30 pg/mL were highly speci fic for pneumococcal AOM. These findings suggest a distinctive role fo r S pneumoniae in the pathogenesis of AOM.