A clinical study of prediction of difficult airway in apparently normal individuals by combining Mallampati test and thyromental distance

Background: Unanticipated difficult airways are an important cause of perioperative morbidity. No single bedside airway assessment test reliably predicts difficult intubation; therefore, combining simple predictors may improve diagnostic accuracy. Aims and Objectives: To evaluate the ability of the modified Mallampati test (MMT) and thyromental distance (TMD), individually and in combination, to predict difficult laryngoscopy and to identify the most reliable bedside screening method in apparently normal adults undergoing elective surgery. Materials and Methods: This prospective observational analytical study included 100 American Society of Anesthesiologists I–II patients aged 20–55 years scheduled for elective surgery under general anesthesia. Pre-operative airway assessment was performed using the MMT and TMD as primary predictors, whereas sternomental distance (SMD), inter-incisor distance (IID), and upper lip bite test (ULBT) were evaluated as secondary comparators. Direct laryngoscopy was performed by a blinded anesthesiologist and graded using the Cormack–Lehane classification as the reference standard. Diagnostic indices, including sensitivity, specificity, positive predictive value, negative predictive value (NPV), and accuracy, were calculated. Results: Most patients were aged 20–35 years (66%), males (53%), and had normal body mass index (67%). More patients had easy airway predictors, with MMT Class I–II in 81% and TMD ≥6.5 cm in 88%. MMT correctly identified 10 of 11 difficult airways (sensitivity 90.90% and NPV 98.76%), whereas TMD showed higher specificity (96.62%) and accuracy (95%). SMD and IID demonstrated high specificity but low sensitivity, whereas ULBT showed moderate predictive value. The combined MMT+TMD detected all difficult laryngoscopies with only one false positive, achieving an accuracy of 99%. Conclusion: The combined MMT and TMD assessment provides a simple, rapid, and highly accurate method for predicting difficult airways and should be incorporated into routine pre-operative evaluation.