Precision of tympanometric measurements

In both scientific and clinical investigations, precision of instruments is demanded. Precision of tympanometric measures has been reported in the literature rarely, and studies are generally not comparable. This study introduces a new method of determining precision of tympanometric variables. Forty-three participants in good health were investigated. Static compliance, middle ear pressure, and gradient were recorded in a test-retest design. Plots of test versus retest measurements were constructed For each variable, after which differences between measurements were plotted against their means. The standard deviation of the distribution of differences provides a measure of precision: the coefficient of repeatability. Static compliance showed a significant disagreement between measurements; hence repeatability was poor, which can be explained by preconditioning of the tympanic membrane. Middle ear pressure and gradient showed good agreement between measurements, and comparable measures of precision are reported. The method is simple and based on two repeated measurements in each subject; the design is ethical and practical in clinical investigations.