Predictive value of tympanometry in middle ear effusion.

The presence of middle ear effusion may be inferred from a tympanogram by the configuration of the pressure compliance curve. Not infrequently, however, effusion is absent at the time of surgery when strongly indicated by preoperative tympanometry. We evaluated this discrepancy by contrasting preoperative tympanograms with the findings at surgery in 462 children, aged 4 to 8 years, with clinical evidence of persistent effusion in 909 ears. Based on these results we can classify tympanograms as to high risk for effusion, intermediate, and low risk. The proportion of ears with effusion was 83%, 47%, and 34%, respectively. The proportion of ears with fluid in the high risk tympanogram group did not change appreciably over a 1- to 8-week period, ie, no trend toward spontaneous resolution occurred. The high incidence of effusion at surgery in our low risk group is far higher than expected and is presumably due to reinfection of these ears during the time between examination and operation.