Background : With respect to the frequency of difficult intubation and its known complications, the present study was conducted in Matini hospital in Kashan to determine the value of predictive tests.

Materials and methods : This descriptive study was carried out on 379 patients referring for surgery. During the first preoperation visit Mallampati test was achieved and patients were categorized in either I to IV classes. Then the thyromental distance was measured. Induction was managed by sodium thiopental 5mg/kg and succinile choline 1.5mg/kg, then laryngoscopic view was determined according to the Cormack classification. Those who were classified as grade III or IV in Mallampati test or had thyromental distance of less than 6cm were considered as at risk patients for intubation. Those who fell in Cormack III of IV classification were considered as difficult intubation. Finally, sensitivity, specificity, positive and negative predictive values of these tests were calculated.

Results : The study population included 179 males and 200 females with the mean age of 45.1±22.4 years. Of 379 patients, 29 (7.7%) were revealed to have difficult intubation. Positive and negative predictive values of Mallampati test was 12% and 93%, respectively, however, these values were 9.8% and 92.7% for Thyromental test.

Conclusion : With respect to the low sensitivity and PPV of Thyromental and Mallampati tests, they are of limited value for detection of difficult intubation