Predictive performance of thyromental height for difficult laryngoscopies in adults: a systematic review and meta-analysis

Abstract

Background: Thyromental height (TMH) was first reported as a great single test for prediction of difficult laryngoscopies, although further studies have shown variable estimates of its accuracy. We thus performed this meta-analysis to summarize the predictive values of TMH mainly for prediction of difficult laryngoscopies. Methods: A search in PubMed, EMBASE, LILACS, and Scielo was conducted in June 2020. We included prospective cohorts fully reported with patients ≥ 16 years old, providing data on predictive values of TMH for prediction of either difficult laryngoscopies or difficult intubations. Diagnostic properties and association between TMH and Cormack and Lehanes’s classification by direct laryngoscopy were evaluated. A random-effects meta-analysis using hierarchical models was performed. Results: Eight studies evaluating 2844 patients were included. All included studies had high risk of bias and low concern regarding applicability. There was significant heterogeneity among the studies. The pooled diagnostic odds ratio (DOR) and positive (LR+) and negative (LR-) likelihood ratios were as follows: DOR, 57.94 (95% CI: 18.19–184.55); LR+, 11.32 (95% CI: 4.28–29.92); and LR-, 0.23 (95% CI: 0.15–0.35). Summary sensitivity and specificity for studies with common threshold were 82.6 (95% CI: 74–88.8%) and 93.5 (95% CI: 79–98.2%), respectively. The estimated AUC was 81.1%. Conclusion: TMH arises as a good predictor of difficult laryngoscopies in adult patients from diverse populations presenting better predictive values than most previously reported bedside tests. However, the high risk of bias throughout the studies may have skewed the results of the individual research as well as the summary points of the present meta-analysis.