Authors: Ali M et al.
Cureus, June 18, 2026.
Summary
This prospective observational study compared the modified Mallampati score with ultrasound measurement of the skin-to-epiglottic distance for predicting difficult glottic visualization during direct laryngoscopy.
The study included 400 adults between 18 and 60 years old undergoing elective surgery with general anesthesia and endotracheal intubation. All patients were classified as ASA physical status I or II. Patients with a body mass index above 35 kg/m², limited mouth opening, maxillofacial abnormalities, rapid-sequence induction requirements, tracheostomies, or inability to cooperate were excluded.
Before surgery, each patient underwent a modified Mallampati examination and an airway ultrasound. The ultrasound probe was placed transversely over the thyrohyoid membrane, and the distance from the skin to the epiglottis was measured at end expiration. Three measurements were obtained and averaged.
During direct laryngoscopy, glottic visualization was graded using the Cormack-Lehane system. Grades I and II were considered easy visualization, while grades III and IV were considered difficult.
Of the 400 patients, 368 had easy glottic visualization and 32 had difficult visualization. The skin-to-epiglottic distance increased progressively as the laryngoscopic view worsened:
Cormack-Lehane grade I: 17.12 mm
Cormack-Lehane grade II: 18.94 mm
Cormack-Lehane grade III: 20.71 mm
Cormack-Lehane grade IV: 22.17 mm
All comparisons between the different Cormack-Lehane grades were statistically significant.
The ultrasound measurement substantially outperformed the modified Mallampati score. The area under the receiver operating characteristic curve was 0.98 for the skin-to-epiglottic distance, compared with only 0.50 for the Mallampati score.
Using a skin-to-epiglottic distance cutoff greater than 19.5 mm produced:
100% sensitivity
89.95% specificity
46.38% positive predictive value
100% negative predictive value
In comparison, a Mallampati score greater than 3.5 produced:
6.25% sensitivity
99.46% specificity
50% positive predictive value
92.42% negative predictive value
On multivariable analysis, skin-to-epiglottic distance was the only independent predictor of difficult laryngoscopy. Age, sex, body mass index, and Mallampati score were not independently predictive.
What You Should Know
Ultrasound-measured skin-to-epiglottic distance was far more accurate than the modified Mallampati score for predicting difficult glottic visualization.
A measurement greater than 19.5 mm identified every difficult laryngoscopic view in this study, giving it 100% sensitivity and a 100% negative predictive value.
The relatively low positive predictive value means that not every patient with an increased skin-to-epiglottic distance will actually have a difficult laryngoscopy. The measurement may therefore be most useful for ruling out difficulty rather than confirming it.
The modified Mallampati score performed poorly, with sensitivity of only 6.25% and an area under the curve equivalent to chance.
The proposed 19.5-mm cutoff may be specific to the Pakistani or broader South Asian population. Different studies have reported cutoffs ranging from approximately 15.5 mm to more than 25 mm, likely because of ethnic and anthropometric differences.
Important limitations include the single-center design, convenience sampling, use of only one ultrasound operator, exclusion of patients with a BMI above 35 kg/m², and the relatively small number of difficult laryngoscopies.
The results support using airway ultrasound as an adjunct to standard airway assessment, but they do not justify completely replacing a comprehensive clinical airway evaluation.
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