POINT AND PERIOD PREVALENCE OF OTITIS-MEDIA WITH EFFUSION EVALUATED BY DAILY TYMPANOMETRY

Previous studies on daily tympanometric screening using an automatic impedance tympanoscope indicated relatively high incidences of type B tympanograms of one day's duration, which is contrary to our conceptions of the pathogenesis and pathology of otitis media with effusion. We therefore repeated the study in 51 otherwise healthy children (100 ears) attending kindergarten. Tympanometry was performed daily for one month using both the conventional impedance apparatus AZ 7 and the automatic impedance tympanoscope ZS 331. The impedance apparatus did not indicate any one-day type B tympanograms and only a few short-lasting episodes occuring either in the beginning or end of the study period. Several ears had type B tympanograms on all days examined. The point prevalence was 15 per cent and the period prevalence 17 per cent, which accord well with findings of previous epidemiological studies of secretory otitis. The impedance tympanoscope indicated 16 cases of B-curves lasting only one day and considerably higher point and period prevalences, which make the impedance tympanoscope unsuited for both scientific and clinical purposes.