Mallampati class is not useful in the clinical assessment of sleep clinic patients

Abstract

Study Objectives: To assess the utility of Mallampati class, a simple grade of oropharyngeal appearance used to assess difficulty of intubation, to predict severe obstructive sleep apnea and absence of OSA (rule in severe OSA and rule out OSA). Method: Retrospective review of consecutive patients under-going diagnostic polysomnography in a tertiary referral sleep disorders center. Modified Mallampati class and other simple patient characteristics (age, gender, body mass index) were compared to apnea-hypopnea index (AHI). The sensitivity, specificity, and the positive and negative likelihood ratios (LR+ and LR-) were calculated for Mallampati class IV to detect an AHI > 30 (rule in severe OSA) and Mallampati class I to detect an AHI < 5 (rule out OSA). Results: A total of 953 consecutive patients (619 male) under-going diagnostic polysomnography were included. The age of the cohort was 50.0 ± 6.4 years, with a BMI of 33.8 ± 8.6 kg/m2 and AHI of 26.1 ± 25.1 /h (95% Cl 1.4-78.8). Mallampati class was significantly associated with AHI (r = 0.13, p < 0.001), but there were no differences in AHI between Mallampati classes. A Mallampati class IV had a sensitivity of 40%, specificity of 67%, LR+ of 1.21, and LR- of 0.90 for an AHI > 30. A Mallampati class I was only 13% sensitive but 92% specific for an AHI < 5, with LR+ of 1.63 and LR- 0.90. Conclusions: Mallampati class is associated with AHI but does not significantly modify likelihood of severe OSA or absence of OSA. As such, it is of limited use to "rule in" severe OSA or "rule out OSA" in the sleep clinic population.