What is the predictive value of the modified Mallampati test and upper lip bite test in relation to the Cormack and Lehane grading system for anticipating difficult intubation?

From the Guidelines

The modified Mallampati test and upper lip bite test are useful predictors of difficult intubation when correlated with the Cormack and Lehane grading system, but should be used as part of a comprehensive airway assessment. The predictive value of these tests is moderate, with the modified Mallampati test having a sensitivity of approximately 50-65% and specificity of 65-80%, while the upper lip bite test shows slightly better performance with sensitivity around 60-70% and specificity of 80-90% 1. These tests work best when used together, as they evaluate different aspects of airway anatomy: the modified Mallampati test assesses the visibility of oropharyngeal structures (classes I-IV), while the upper lip bite test evaluates mandibular mobility (classes I-III) 1. Both tests correlate with Cormack and Lehane grades, which classify laryngeal view during direct laryngoscopy from grade 1 (full view) to grade 4 (no view), with higher Mallampati or upper lip bite test classes tend to predict higher Cormack-Lehane grades, suggesting difficult intubation. Key factors to consider in airway assessment include:

• Evaluation of thyromental distance
• Neck mobility
• Other predictors of difficult airway Using a combination of these assessments can help identify patients at risk of difficult intubation and guide the choice of intubation technique and equipment, such as the use of videolaryngoscopes or supraglottic devices 1. In clinical practice, a comprehensive airway assessment should be performed to minimize the risk of difficult intubation and optimize patient outcomes.

From the Research

Predictive Value of Modified Mallampati Test and Upper Lip Bite Test

The predictive value of the modified Mallampati test and upper lip bite test in relation to the Cormack and Lehane grading system for anticipating difficult intubation can be evaluated based on several studies.

• The sensitivity and specificity of the modified Mallampati test (MMT) were found to be 66.67% and 96.97%, respectively, in a study published in 2021 2.
• The upper lip bite test (ULBT) had a sensitivity of 77.78% and a specificity of 93.18% in the same study 2.
• A combination of MMT and ULBT improved the sensitivity and specificity to 88.89% and 93.18%, respectively 2.
• Another study published in 2024 found that the upper lip bite test had higher specificity, positive predictive value, and accuracy compared to the modified Mallampati test in predicting difficult laryngoscopy and/or intubation among morbidly obese patients 3.
• The combination of the upper lip bite test and the modified Mallampati test also improved the predictive value in this study 3.

Comparison of Predictive Values

The predictive values of the modified Mallampati test and upper lip bite test can be compared based on various studies.

• A study published in 2017 found that the modified Mallampati score had the highest specificity (94.5%) among the three tests, while the facial angle had the highest sensitivity (87.5%) 4.
• The upper lip bite test was found to have higher sensitivity, specificity, negative predictive value, and accuracy compared to the modified Mallampati test in a study published in 2003 5.
• Another study published in 2015 found that none of the three tests (upper lip bite test, modified Mallampati test, and thyromental distance) were suitable predictive tests when used alone, but combinations of individual tests added some incremental diagnostic value 6.

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Predictive Value in Different Populations

The predictive value of the modified Mallampati test and upper lip bite test may vary in different populations.

• A study published in 2024 found that the upper lip bite test was a favorable test for identifying easy and difficult intubations and laryngoscopies in morbidly obese patients 3.
• Another study published in 2015 found that the combination of the upper lip bite test and the modified Mallampati test improved the predictive value in a population of ASA I and II adult patients undergoing elective surgical procedures 6.
• The predictive value of the modified Mallampati test and upper lip bite test may also vary depending on the specific patient population and the definition of difficult intubation used 2, 4, 5.

Limitations and Future Studies

The studies on the predictive value of the modified Mallampati test and upper lip bite test have some limitations.

• The studies had relatively small sample sizes, which may limit the generalizability of the results 2, 4, 5.
• The definition of difficult intubation varied across studies, which may affect the comparison of results 2, 3, 6.
• Further studies are needed to validate the results and to explore the predictive value of the modified Mallampati test and upper lip bite test in different populations and settings 3, 6.