Comparison of modified Mallampati test and thyromental height test for preoperative airway assessment

Abstract

Background: Prevision of a potentially difficult airway in the preoperative period is imperative. The available tools are evaluation of mouth opening, Mallampati test; atlanto-occipital extension; hyomental, thyromental, and sternomental distances; and upper lip bite test; thyromental height test (TMHT) is a new indicator. Aims: To compare the effectiveness of preoperative anaesthetic airway evaluation methods of TMHT and Modified mallampati test (MMT) to predict the difficulty in intubation. Materials and Methods: A prospective observational study was aimed to compare the effectiveness of preoperative anesthetic airway evaluation methods of TMHT and modified Mallampati test (MMT) to predict the difficulty in intubation. A total of 150 subjects were included in this study. MMT and TMHT were compared, and sensitivity, specificity, predictive values, and accuracy were calculated. Results: On comparison, we found TMHT to be more sensitive (93.33%) than MMT (77.78%); both tests have high specificity (TMHT 91.43%; MMT 81.90%). Positive predictive value was 82.35% for TMHT and 64.81% for MMT. Similarly, negative predictive value was 96.97% for TMHT and 89.58% for MMT. Accuracy was 92.00% for TMHT and 80.66% for MMT. Conclusions: TMHT can predict difficult intubation better than MMT (high positive predictive value). However, both TMHT and MMT predict easy intubations effectively, their negative predictive values being high.