Interferon-gamma in suppurative otitis media: significance of otorrhoea type and disease outcome

Interferon-gamma has been reported to have an immunoregulatory role in otitis media with effusion. However, such a role remains to be determined in acute suppurative otitis media.

To determine the levels of interferon-gamma in middle-ear secretion in children with acute suppurative otitis media, and to determine the significance of interferon-gamma to the nature of otorrhoea and the outcome of otitis media.

Prospective, longitudinal follow up of patients selected from community and tertiary health centres.

We selected children with acute suppurative otitis media, diagnosed as otorrhoea of less than three months' duration. Middle-ear secretions were collected by pipetting and stored at -80 degrees C. Interferon-gamma was assayed using enzyme-linked immunosorbent assay. The patients were treated and followed up for nine to 12 months, to separate those with resolved acute suppurative otitis media from those with chronic suppurative otitis media.

The study initially included 358 cases of acute suppurative otitis media. Nine-month follow up was achieved in 304 patients (85 percent). Of these patients, acute suppurative otitis media resolved in 187 (61 percent), while chronic suppurative otitis media was evident in 117 (39 percent). The children with completed follow up comprised 173 boys and 131 girls, aged between four months and nine years (mean age 6.6 years; standard deviation 1.32). These children had purulent otorrhoea in 171 cases (56 percent) and mucoid otorrhoea in 133 cases (44 percent). The children's middle-ear secretion interferon-gamma concentrations ranged from 12 to 126 pg/ml. The mean middle-ear secretion interferon-gamma concentration was 27.2 pg/ml (standard deviation 8.8) in patients whose acute suppurative otitis media resolved, and 73.1 pg/ml (standard deviation 9.5) in those progressing to chronic suppurative otitis media. In children with purulent otitis media, the mean middle-ear secretion interferon-gamma concentration was 43.5 pg/ml (standard deviation 15.6); in those with mucoid otitis media, it was 74.3 pg/ml (standard deviation 19.1). Univariate analysis revealed significant differences in middle-ear secretion interferon-gamma concentration, comparing resolved acute suppurative otitis media and chronic suppurative otitis media cases (p = 0.00), and comparing purulent and mucoid otitis media cases (p = 0.00). Pearson correlation testing revealed significant inverse correlation between interferon-gamma concentration and middle-ear secretion immunoglobulin G concentration (p = 0.01), immunoglobulin E concentration (p = 0.03) and immunoglobulin A concentration (p = 0.00).

A high concentration of interferon-gamma in middle-ear secretions promotes chronicity of suppurative otitis media. Further research in this area may lead to the development of agents which assist the control of suppurative otitis media chronicity.