Comparison of the modified Mallampati classification score versus the best visible Mallampati score in the prediction of difficult tracheal intubation: a single-centre prospective observational study.

Purpose: The modified Mallampati classification is part of the preoperative airway risk assessment. Inconsistency in the way it is examined may contribute to heterogeneity in its diagnostic performance. The best visible Mallampati score could reduce interobserver heterogeneity but its diagnostic characteristics remain unknown.

Methods: During preoperative anesthesia consultation of adult patients with a senior anesthesiologist, we compared the modified Mallampati classification score vs the best visible Mallampati score using cervical extension, tongue in, and phonation. The primary outcome was the diagnostic characteristic of the modified Mallampati classification score vs the best visible Mallampati score as predictors of difficult orotracheal intubation (more than two direct laryngoscopies or need for an alternate device). We performed a multivariable analysis to identify independent predictors of difficult orotracheal intubation in the tested cohort.

Results: Difficult orotracheal intubation occurred in 77/3,243 (2.4%) patients. A best visible Mallampati score was obtained in 1,596 (49.2%) patients. Sensitivity and specificity of the modified Mallampati classification score for predicting difficult orotracheal intubation were 0.56 (95% confidence interval [CI], 0.44 to 0.66) and 0.69 (95% CI, 0.68 to 0.71), respectively. By comparison, the best visible Mallampati score was less sensitive (difference, -0.30; 95% CI, -0.19 to -0.30; P < 0.001) but more specific (difference, 0.24; 95% CI, 0.22 to -0.25; P < 0.001). In patients with difficult orotracheal intubation, 53% were incorrectly reclassified as low risk by the best visible Mallampati score.

Conclusion: Compared with the modified Mallampati classification score, the best visible Mallampati score decreased sensitivity for predicting difficult orotracheal intubation and falsely classified half of the patients with difficult orotracheal intubation. Taking the risks associated with difficult airways into account, our findings indicate that a careful examination of the modified Mallampati classification is required during the global preoperative airway examination.

Study registration: ClinicalTrials.gov ( NCT02788253 ); 9 February 2016.