Middle ear effusions from 100 patients (ages 6 months to 10 years) with serous otitis media were examined. The IgA, IgG, and lysozyme were demonstrated at a higher level in the effusions than the corresponding sera, indicating local production. The mucoid type contained higher level of immunoglobulins and lysozyme compared to serous type effusions.
Bacteria were found in 77% of the effusions by means of a smear, and 52% yielded positive bacterial culture. The incidence of positive culture in effusions of the patients less than 6 years of age was 60%, while the group older than 6 years old was 32%, and the group over 8 was only 22%. Bacterial recovery rate was inversely related to the dramatic increase with age of IgA and IgG and Iysozyme levels in effusions.