By Lucy Piper
Nocturnal oximetry is an accurate instrument for detecting and diagnosing sleep apnea syndrome (SAS) in patients with stroke, research indicates.
This screening instrument may offer physicians a good alternative to polysomnography, the standard diagnostic test, which is often not feasible in stroke rehabilitation settings because it is costly to use, requires technical expertise, and is an added burden for the patient, the researchers comment.
They found that nocturnal oximetry predicted SAS with a sensitivity of 77% and a specificity of 100%.
"Given the high prevalence of SAS in stroke, a positive oximetry result increased the likelihood of SAS to 100%, whereas a negative result lowered the probability to 17%," lead researcher Justine Aaronson (Heliomare Research and Development and Heliomare Rehabilitation Center, the Netherlands) and colleagues report.
The team analyzed sleep recordings obtained for 56 stroke patients. Of these, 46% had SAS diagnosed, predominantly obstructive apneas. The majority (78%) of SAS patients were male and they tended to be older and have a higher body mass index (BMI) than patients without SAS.
At an oxygen desaturation index (ODI) of 15 or above, pulse oximetry predicted SAS with a sensitivity of 77% and a specificity of 100%. Lowering the ODI to 5 or above increased sensitivity to 96%, but the specificity declined to 43%.
The researchers note in Stroke that the clinical variables of age, gender, and BMI all correlated significantly with the apnea-hypopnea index (AHI), but it was scores on the ODI that explained the vast majority of variance in AHI, at 87%.
Indeed, "age, gender, and BMI did not significantly add to the predictive value of oximetry," they report.
"Further validation of oximetry in larger samples is required to determine whether our findings can be generalized to other stroke samples," the team concludes.
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