Diagnostic Accuracy of Upper Lip Bite Test Versus Modified Mallampati for Predicting Difficult Airway in Patients coming for Surgery in a Tertiary Care Hospital

Abstract

Objective: This study aimed to compare the diagnostic accuracy of the ULBT and MMT for predicting difficult laryngoscopy when using the Cormack and Lehane (CL) grading system as the gold standard.

Study Design: Cross-sectional validation study
Place and Duration of Study: This study was conducted at the Shifa International Hospital, Islamabad, during October 2025 till March 2026.

Methods: This study conducted on 211 patients undergoing elective surgery under general anesthesia. Pre-operative airway assessments like MMT and ULBT were performed by the primary investigator. During surgery a second anesthesiologist did laryngoscopy and recorded the CL grade. Diagnostic accuracy indices such as the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy were calculated and compared for both tests.

Results: Difficult airways (CL grade 3) were seen in 22 patients (10.4%). The ULBT had a superior diagnostic performance compared to the MMT across all indices. ULBT had a sensitivity of 86.4%, specificity of 96.3% and accuracy of 95.3% (AUC 0.887). In contrast, the MMT showed lower sensitivity (77.3%), specificity (82.5%) accuracy (82.0%; AUC 0.804), with a notably low PPV (34.0%) indicating a high false-positive rate.

Conclusion: Upper Lip Bite Test proved to be a more accurate and reliable bedside predictor of difficult laryngoscopy than the Modified Mallampati Test.