Objective To evaluate the screening efficiency of four variable score for moderate to severe obstructive sleep apnea (OSA) and improve it, and evaluate the screening value of four variable score combined with waist to height ratio (WHtR).

Methods A total of 108 patients suspected by moderate to severe OSA were selected as the study objects, the four-variable score was completely completed, and the polysomnea monitoring was performed all night. According to the sleep hypopnea index (AHI), the patients were divided into the moderate and severe OSA group and non-OSA group. The screening efficacy of modified four-variable score was evaluated by increasing and adjusting the cut-off value of age, gender and age scores, and cut-off value of the total score of four variables, AUC, Yoden index, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the scale. The WHtR cut-off value was determined by combined diagnosis with WHtR

Results The Yoden index, AUC, sensitivity, specificity, PPV and NPV of four variable score for moderate to severe OSA screening were 0.36, 0.68, 96.39%, 40.00%, 84.2% and 76.9%, respectively. When the improved four variable score (male score = 2 points, age ＞45 years old score = 2 points and other screening questions and scoring criteria remaining unchange) was ≥11 points, the higher Yoden index and AUC were obtained, which were 0.47 and 0.73, respectively. When the four variable score was combined with WHtR, the optimal Yoden index and AUC were obtained, which were 0.62 and 0.81, respectively.

Conclusions The original four-variable score has a general screening effect on moderate to severe OSA, but the improved four-variable score can be used to obtain better screening efficacy. It is recommended that the total score ≥11 points should be set as the cut-off value, and the combined diagnosis with WHtR is recommended. Patients with improved four-variable score ≥11 points and WHtR＞0.50 are the high-risk patients with moderate to severe OSA