Comparison of modified mallampati classification, upper lip bite test and neck circumference in prediction of difficult intubation

Aim of the study: In this prospective study, we aimed to assess the sensitivity, specificity, accuracy and positive/negative predictive values of Modified Mallampati classification, upper lip bite test and neck circumference compared to Cormack and Lehane grading system, in predicting difficult intubation.Methods: ASA physical status I-II, aged 18-60 years, 185 patients were enrolled in this study. Modified Mallampati classification, upper lip bite test and neck circumference of the patients were recorded before induction of anaesthesia. Laryngoscopic views according to the Cormack and Lehane grading system were determined after induction of anesthesia.Results: The incidence of difficult intubation was 8,1 according to Cormack-Lehane grade 3 or 4. We did not find any significant correlation between Cormack and Lehane classification and neck circumference. Sensitivity, specificity, and accuracy as calculated were 26,6%, 94% and 88,6% for modified Mallampati classification, and 13%, 97,6 % and 90,8%, respectively for the upper lip bite test. Additionally, it was observed that the specificity increased while sensitivity decreased when the two tests were combined; but there was no change in positive predictive value.Conclusion: Modified Mallampati classification and the upper lip bite test are more useful in prediction of easy intubation and laryngoscopy with high specificity and negative predictive value. Alone or in combination, the tests are not adequate in detection of difficult intubation. It should be considered that accurate detection of difficult intubation is not possible, and clinicians must be prepared for unanticipated difficult intubation.Key words: Difficult laryngoscopy, modified Mallampati classification, the upper lip bite test, neck circumference