Validity of tympanometry for middle ear effusions.

The findings on paracentesis and aspiration of the middle ear were compared with preoperative tympanometry. From the results obtained, it was found that if tympanometry alone is used to determine the presence or absence of fluid the best discriminant is a compliance of 0.21 or a gradient of 0.04 equivalent volume units. The average failure rate with either or these criteria is 20%. A numerical estimate of the validity of tympanometry may be made for individual cases.