Prediction of difficult intubation: is there a gold standard?

Background: Failure to maintain a patent airway after induction of general anesthesia remains a common cause of anesthesia-related mortality. Because of potentially serious consequences of failed tracheal intubation, considerable attention has been focused on methods to predict patients in whom laryngoscopy and intubation might be difficult.Combination of different test and scores are developed, but none of them have proven to be totally reliable. Methods: We evaluated the relationship between preoperative airway assessment scores used in common practice, by comparing modified Mallampati, upper lip bite test andThyromental distance with glottis exposure obtained during direct laryngoscopy in 250 patients.Results: The incidence of difficult intubation in our trial was (43) 17.2%. Of these only 27 were correctly predicted as difficult by Modified Mallampati test where as only 2 were predicted as difficult by Upper lip bite test and 39 were predicted by Thyromental distance.Conclusion: Among the three indices, Thyromental distance has got highest sensitivity (90.7%) and specificity (94.6%). However, it is better to combine all three indices for accurate prediction of difficult intubation.