Comparative analysis of 226 Hz and 1 000 Hz probe tone tympanometry in infants

OBJECTIVE: To analyze the judgement standard and evaluate the diagnostic value of the low frequency and high frequency tympanometry in infants with otitis media. METHOD: Tympanograms for admittance with 226 Hz and 1 000 Hz probe tones and resonant frequency were obtained from normal infants (195 cases, 321 ears) and infants with otitis media(122 cases, 171 ears). The mean, standard deviation, median, 5% quantile, 95% quantile and 95% confidence interval of peak admittance, gradient and resonant frequency were measured and calculated in different age groups. The significant differences of 1000 Hz peak admittance, 226 Hz peak admittance and gradient between normal infants and infants with otitis median were analyzed using SPSS 11.0. The false positive rate and the false negative rate of different age groups in infants with otitis media were evaluated according to such judgement standards as 1000 Hz peak admittance, 226Hz peak admittance or gradient. RESULT: The false positive rate and the false negative rate of the 1000 Hz probe tone tympanometry in infants with otitis media unter one year of age were 3.07% and 1.84% as the normal range of positive peak was more than 0.2 mmho. The false positive rate and the false negative rate of the 1000 Hz probe tone tympanometry in infants with otitis media aged 1-2 years and aged 2-3 years were 3.26%, 5.26% and 1.52%, 0.00% respectively,as the normal range of positive peak was more than 0.3 mmho. These was no significant difference in the gradient with 226 Hz probe tone between normal infants and infants with otitis median under one year of age. The false positive rate and the false negative rate of the 226 Hz probe tone tympanometry in infants with otitis media aged 1-2 years and aged 2-3 years were 44.57%, 31.58% and 16.67%, 6.67% respectively, as the gradient with 226 Hz probe tone was a judgement standard. CONCLUSION: (1) The diagnostic accuracy of tympanometry with 1000 Hz probe tone for otitis media in infants younger than 3 years of age exceeded 226 Hz probe tone tympanometry, the 1000 Hz probe tone tympanometry is suggested to the evaluation of middle ear function in infants before 3 years. (2) It is reasonable that the normal range of positive peak is more than 0.2 mmho in infants unter one year of age and the normal range of positive peak is more than 0.3 mmho in infants aged 1-3 years.