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Positive Predictive Value of Upper Lip Bite Test in Predicting Difficult Intubation

Objective: To determine the positive predictive value of upper lip bite test in predicting difficult intubation by taking Cormack and Lehane classification as gold standard. Design of the Study: Cross sectional study. Study Settings: This cross-sectional study was conducted at Department of Anesthesiology, Sir Ganga Ram Hospital, Lahore from 04/06/2021 to 03/12/2021. Materials and Methods: This study involved 313 patients of both genders, aged between 18-70 years undergoing general anesthesia on elective lists having positive upper lip bite test (Grade-III). On the basis of Cormack and Lehane Classification, the diagnosis was verified. Results of the ULBT were compared to the Cormack and Lehane grade-III and grade-IV diagnoses. Every patient's written informed permission was obtained. Results: In The mean age of the patients was 43.78±12.32 years. Majority (n=150, 47.9%) of the patients were aged between 36-52 years. There were 198 (63.3%) male and 115 (36.7%) female patients in the study group. Among the procedures, herniorrhaphy (32.9%) and cholecystectomy (26.8%) were the more frequent procedures followed by thyroidectomy (17.6%), tonsillectomy (13.1%) and mastectomy (9.6%). Majority (42.8%) of the patients belonged to ASA Class-I followed by ASA Class-II (29.7%) and ASA Class-III (27.5%). Difficult intubation was confirmed in 232 (74.1%) patients on Cormack and Lehane Classification (as per operational definition). Thus there were 232 true positive patients with 81 false positive patients. With the gold standard Cormack and Lehane Classification, the upper lip bite test yielded a positive predictive value of 74.1 percent in the prediction of difficult intubation. Conclusion: According to the gold standard of Cormack and Lehane Classification, an upper lip bite test (Grade-III) has a 74.1 percent positive predictive value for difficult intubation in patients undergoing general anaesthesia with endotracheal intubation on the elective list. Keywords: Difficult Intubation, Cormack and Lehane Classification, Upper Lip Bite Test