Comparative Evaluation of Diagnostic Accuracy of TMHT (Thyromental Height Test), As Predictor of Difficult Laryngoscopy with Other Predictors (Modified Mallampati, Interincisor Gap, Thyromental Distance, Neck Circumference, And Neck Extension).

Abstract

Background and Aim: Thyromental height test (TMHT) is a recently described anatomical bedside screening tool in predicting difficult laryngoscopy. It has been shown to be more accurate than the modified Mallampati score, thyromental distance (TMD), and sterno-mental distance with regard to sensitivity and positive predictive value (PPV). We attempted this study to evaluate the diagnostic accuracy of Thyromental height test as a predictor of difficult laryngoscopy pre-operatively and compare with other predictors.

Methods: This prospective, observational, single blind study was conducted in our teaching hospital on 139 patients. TMHT along with other bedside predictors of difficult intubation, including modified Mallampati score, interincisor gap (IIG), TMD, neck circumference (NC), and neck extension were assessed. We compared the sensitivity, specificity, PPV, negative predictive value (NPV), and diagnostic accuracy of TMHT with other bedside tests such as the modified Mallampati score, IIG, TMD, NC, and neck extension individually in predicting difficult laryngoscopy. Any Cormack and Lehanne’s intubation grade II b and above were considered to be difficult laryngoscopy.

Results: TMHT had the highest specificity of 82.9% and sensitivity of 69.8. TMHT had the most accuracy of 77% when compared with the modified Mallampati score, IIG, TMD, NC, and neck extension. TMHT was followed by the modified Mallampati score and IIG.

Conclusion: TMHT appears as a promising measure to predict the risk of difficult laryngoscopy, however, validation will require further studies in more diverse patient populations.