Evaluation of the reliability of preoperative descriptive airway assessment tests in prediction of the Cormack-Lehane score: A prospective randomized clinical study.

Study Objective: In this study we investigated and compared the predictive values of different airway assessments tests including thyromental height measurement test, which has been recently suggested, in difficult laryngoscopy (Cormack and Lehane [C-L] scores 3 and 4). In addition, we compared the effectiveness of methods and C-L scores, by IDS, in terms of predicting difficult intubation.

Design: Prospective, blinded study.

Setting: Maltepe University.

Patients: Four hundred fifty-one patients selected randomly who underwent general anesthesia.

Interventions: In this study we compared predictive value of thyromental height measurement test (TMH), which has been recently suggested, modified Mallampati test (MMT), upper lip bite test (ULBT), and thyromental distance measurement test (TMD) in difficult laryngoscopy. Final C-L scores were compared with intubation difficulty scale (IDS) in terms of predicting difficult intubation.

Measurements: Patient's American Society of Anesthesiology score, age and weight were recorded. TMH, TMD, MMT, ULBT, IDS and C-L scores were measured and determined.

Main Results: The optimal cut-off point for TMH for predicting difficult laryngoscopy was 43.5 mm and for TMD was 82.06 mm. Use of TMH <43.5 with MMT has the highest sensitivity for predicting difficult intubation (78.38) with 75.36% specificity and 97.50% negative predictive value. TMH showed sensitivity of 91.89% and specificity 52.17% at 50 mm cut-off value. In the comparison of the area under the receiver operating characteristic curve values, none of the tests came forth individually or in combination with MMT test.

Conclusions: The present study demonstrates the practicality of TMH as a digitalized test however the clinical benefits of TMH in daily medical practice are drawn into question. The additional variable of race may have had some bearing on this and further studies, larger in patient sample size, may need to use different methodology concerning age-, sex-, and race-dependent variables in evaluating these tests.