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

Abstract

AbstractBackground:Interferon-γ 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.Aim:To determine the levels of interferon-γ in middle-ear secretion in children with acute suppurative otitis media, and to determine the significance of interferon-γ to the nature of otorrhoea and the outcome of otitis media.Settings and design:Prospective, longitudinal follow up of patients selected from community and tertiary health centres.Methods: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°C. Interferon-γ 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.Result:The study initially included 358 cases of acute suppurative otitis media. Nine-month follow up was achieved in 304 patients (85 per cent). Of these patients, acute suppurative otitis media resolved in 187 (61 per cent), while chronic suppurative otitis media was evident in 117 (39 per cent). 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 per cent) and mucoid otorrhoea in 133 cases (44 per cent). The children's middle-ear secretion interferon-γ concentrations ranged from 12 to 126 pg/ml. The mean middle-ear secretion interferon-γ 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-γ 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-γ 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-γ concentration and middle-ear secretion immunoglobulin G concentration (p = 0.01), immunoglobulin E concentration (p = 0.03) and immunoglobulin A concentration (p = 0.00).Conclusion:A high concentration of interferon-γ 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.