Sensitivity and specificity of diagnostic tests for impaired nasal respiration.

Diagnostic tests are imperfect and vary in their sensitivity and specificity. The degree of imprecision may be calculated to yield probability estimates of accuracy for both the positive and negative predictions of tests under various conditions. Such information enables clinicians to decide whether to accept or reject test results or the tests themselves. Two pilot studies are reported to establish the diagnostic potential of cephalometric measurements and nasal resistance values for the identification of upper airway impairment. A linear estimate of adenoid size and an area index of adenoid encroachment in the nasopharynx were evaluated as diagnostic tests for increased nasal resistance. The sensitivity of the tests was 31.8% and 18.2%, while specificity was calculated at 83.3% and 66.6%, respectively. In the second study, nasal resistance was evaluated as a test to identify persons whose respiratory mode was equal to or less than 75% nasal airflow. At a NRz value of 5.0 cm H2O per liter per second, the sensitivity of this test was 41.2% and the specificity was 84.0%; with the critical value of NRz at 3.5 H2O per liter per second, the sensitivity was 64.7% and the specificity was reduced to 60.0%. The results suggest that these tests are too imprecise for the reliable identification of either those who might benefit from treatment or those for whom treatment is unlikely to yield benefits.