Measurement properties of a screening questionnaire of obstructive sleep apnea risk: Little information, great prediction?

Introduction: Previous research had shown the suitability of several questionnaires predicting the obstructive sleep apnea syndrome. Measurement properties of an online screening questionnaire were studied. Methods: The sample consisted of 184 Portuguese adults (89 men and 95 women); 46 of them were polysomnographically diagnosed with the untreated obstructive sleep apnea syndrome. The participants were assessed with an online questionnaire of sleep apnea risk, from University of Maryland. Results: A principal component factor analysis was performed, revealing a single factor (49.24% of the total variance). Internal consistency was minimally adequate (α40.74). The mean of inter-item correlation was of 0.35 (0.12<r>0.61), whereas the item-total correlations were considered good (0.52<r>0.81). The total score for patients was significantly higher than for healthy participants (p<0.000), but no significant statistical differences between severity groups of patients were found (p>0.05). Furthermore, the ability of the measure in discriminating between healthy subjects and OSA subjects was good. Overall data from the Rasch analysis was consistent with the guidelines of Linacre, scores show good model fit and psychometric adequacy. Conclusions: The measure showed an adequate structural, internal and criterion validity, suggesting this as a useful and effective screening for sleep apnea risk in Portuguese adults.