title: Prediction of ease of laryngoscopy and intubation-role of upper lip bite test, modified mallampati classification, and thyromental distance in various combination.
abstract: BACKGROUND
  The incidence of difficult intubation in patients undergoing general anaesthesia is estimated to be approximately 1-18% whereas that of failure to intubate is 0.05-0.35%.1,2,3 Various methods have been used for prediction of difficult laryngoscopy. Although, upper lip bite has been shown to be a promising test in its introductory article, repeated validation in various populations is required for any test to be accepted as a routine test. We have compared upper lip bite test (ULBT), modified Mallampati test (MMC) and thyromental distance (TMD) individually and in various combinations to verify which of these predictor tests are significantly associated with difficult glottic exposure.
  
  
  METHODS
  After obtaining institutional ethics committee approval, 402 ASA I and II adult patients undergoing elective surgical procedures requiring endotracheal intubation were included. All the three test were performed in all the patients preoperatively and their glottic exposure was recorded by Cormack-Lehane classification during intubation. Sensitivity, specificity, positive predictive value and negative predictive value were used for comparison.
  
  
  RESULTS
  In our study, the incidence of difficult laryngoscopy was 11.4% and failure to intubate 0.49%. None of the three are a suitable predictive test when used alone. Combination of tests added incremental diagnostic value.
  
  
  CONCLUSIONS
  We conclude that all three screening tests for difficult intubation have only poor to moderate discriminative power when used alone. Combinations of individual tests add some incremental diagnostic value.
authors: Bhabha Atomic Centre, King Edward Memorial Hospital, Mumbai, India.
authors: Anjana S
authors: AS
authors: Wajekar
authors: Department of Anaesthesia, Bhabha Atomic Research Centre Hospital, Mumbai, Maharashtra, India.
authors: Shrividya
authors: S
authors: Chellam
authors: Department of Anaesthesia, Bhabha Atomic Research Centre Hospital, Mumbai, Maharashtra, India.
authors: Pratibha V
authors: PV
authors: Toal
keywords: Difficult airway; Mallampati classification; thyromental distance; upper lip bite test