WASHINGTON, DC—The Four-Variable Screening Tool may be a useful method of screening for obstructive sleep apnea within 90 days of stroke, according to study results presented at the 67th Annual Meeting of the American Academy of Neurology. The variables that the test analyzes (ie, BMI, gender, blood pressure, and snoring) may be important predictors of sleep apnea within three months of stroke.
The Four-Variable Screening Tool was the strongest predictor of obstructive sleep apnea compared with other paper-based tools that the study examined, said Mark Boulos, MD, Assistant Professor at the University of Toronto and staff neurologist at Sunnybrook Health Sciences Centre in Toronto. The tool may help determine which patients would most benefit from further evaluation for sleep apnea in the post-stroke setting, he added.
Mark Boulos, MD
Obstructive sleep apnea is common after stroke and, if left untreated, is associated with recurrent vascular events, poor functional outcomes, and mortality. In an ongoing prospective study, Dr. Boulos and colleagues are evaluating the Four-Variable Screening Tool, the Epworth Sleepiness Scale, the SOS score, the STOP-BANG questionnaire, and the Berlin questionnaire as simple paper-based methods for identifying obstructive sleep apnea among patients with stroke. Stroke onset had occurred within 90 days of enrollment for all eligible patients.
Participants underwent ambulatory sleep monitoring using the ApneaLink Plus device, which has been validated against full polysomnography. Patients completed each of the five paper-based screening tools within 72 hours of the ambulatory sleep testing. In this study, the primary definition for clinically relevant obstructive sleep apnea was an apnea–hypopnea index (AHI) of 15 or greater, or an AHI of 5 to 14 with a lowest nocturnal oxygen desaturation of 88% or less. The authors also examined a secondary definition of clinically relevant obstructive sleep apnea, which was an AHI of 15 or greater. The investigators calculated the area under the curve (AUC), sensitivity, and specificity for detecting clinically relevant obstructive sleep apnea for each of the screening tools.
Dr. Boulos presented data for the first 44 patients. Apart from gender, the researchers found no clinically relevant differences between participants with and without sleep apnea.
Using the primary definition of clinically relevant obstructive sleep apnea, the Four-Variable Screening Tool was the only test that demonstrated significant results. It had the greatest AUC (0.878) of all the tests. When the researchers chose a cutoff of 7, the Four-Variable Screening Tool had a sensitivity of 91% and a specificity of 70%. Using a cutoff of 9, the tool had a sensitivity of 65% and a specificity of 90%.
Using the secondary definition for obstructive sleep apnea, the Four-Variable Screening Tool remained a significant predictor of clinically relevant sleep apnea, but had a lower AUC (0.787). Using a cutoff of 7, the tool had a sensitivity of 100% and a specificity of 45%. Using a cutoff of 9, the tool had a sensitivity of 77% and a specificity of 70%.
—Erik Greb