Tympanometry provides a rapid, non-invasive and objective assessment of mid
dle ear (ME) status and is widely used for the clinical diagnosis and follo
w-up of otitis media with effusion (OME). ME pressure, acoustic admittance
and tympanometric gradient are the main test parameters used in making assi
gnments to diagnostic classes (i.e. presence or absence of effusion, effusi
on quantity). Of these, the tympanometric gradient was suggested to be more
sensitive to the presence of effusion, but this has not been demonstrated
conclusively and no standard definition of that gradient is accepted. In th
is study, 10 cynomolgus monkeys with experimental OME were used to compare
the diagnosis of OME made using three different methods to estimate tympano
metric gradient with that provided by simultaneous magnetic resonance imagi
ng (MRI) of the ME. All three methods of tympanometric gradient measurement
were highly correlated with the quantity of ME effusion measured by the MR
I. Although not significant, the MRI results were better correlated with th
ose for the 'width' method when compared to either the 'difference' or the
'ratio' method of gradient estimation. This study demonstrates the use of M
RI as a gold standard for evaluating the accuracy of other methods to diagn
ose ME effusion.