BACKGROUND: Severe obstructive sleep apnea (sOSA) represents a risk factor of postoperative complications. Perioperative sleep apnea prediction (P-SAP) and DES-obstructive sleep apnea (DES-OSA) (DES being the acronym for 2 of the participating investigators and OSA for obstructive sleep apnea) scores were validated in the detection of such patients. They include the measurement of neck circumference (NC) and distance between thyroid and chin (DTC). The aim of this study was to evaluate the influence of the measurement method of NC and DTC on the ability of the 2 scores to detect sOSA. METHODS: A total of 371 preoperative patients were enrolled. For each of them, 6 combinations of P-SAP and DES-OSA scores were evaluated. We compared the results of the 6 combinations with the data extracted from the polysomnography (PSG) if available. The ability of the score to detect sOSA patients was evaluated using sensitivity (Se), specificity (Sp), Youden index (YI), area under receiver operating characteristic curve (AUROC), the Probit model, and the Kappa coefficient of Cohen. A P < .05 was considered as significant, a Bonferroni correction was applied if needed. RESULTS: Three hundred and seventy-one patients had a PSG. The Se and the Sp of the DES-OSA score, and the Sp of the P-SAP score, in their ability to detect severe OSA patients, were influenced by the measurement method of the DTC and of the NC. Nevertheless, the AUROC, the Youden index, the Probit model, and the Kappa coefficient of Cohen are not influenced by the variability of measurement. CONCLUSIONS: This study highlights that the measurement method of NC and DTC can influence the results of the 2 scores. We conclude that a strict protocol for the measurement of NC and DTC should be applied (DTC measurement should be performed on a patient with a head in neutral position and the NC measurement should be performed at the cricoid level).