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Diagnostic Value of Screening Instruments for Identifying Obstructive Sleep Apnea in Kidney Failure
Study Questions:
What is the validity of screening surveys in identifying obstructive sleep apnea (OSA) in patients with chronic kidney disease (CKD)?
Methods:
This is a prospective, observational study of a consecutive cohort of adults with CKD (estimated glomerular filtration rate <60 ml/min/1.73 m2) and end-stage renal disease (ESRD) attending outpatient nephrology clinics and dialysis units in Calgary, Canada. No inclusion or exclusion criteria were set with respect to comorbidities or medications, which improved the generalizability of these findings. Between May 2007 and November 2010, 657 candidates were screened and 173 patients (CKD: n = 109; ESRD: n = 63) completed the study. All patients completed the Berlin Questionnaire (BQ), adjusted neck circumference (ANC), and the STOP-BANG questionnaire. Diagnosis of OSA was made by performing an unattended overnight cardiopulmonary monitor study at home. Sleep apnea was defined as a respiratory disturbance index [RDI] ≥15 calculated by number of oxygen desaturations >4% per hour of monitoring. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for the BQ, ANC, and STOP-BANG.
Results:
The two groups had a similar clinical profile: approximately two-thirds were men, averaging 61-65 years of age. Patients with CKD and ESRD diagnosed with OSA were more likely to have higher body mass index, larger neck circumference, and lower mean nocturnal oxygen saturation. OSA was present in 41 CKD patients (38%) and 32 ESRD patients (51%). All screening instruments had satisfactory sensitivity (56-94%), but poor specificity (29-77%) and low accuracy (51-69%) in both CKD and ESRD patients with RDI ≥15. Using an RDI ≥30 yielded similar results.
Conclusions:
The authors concluded that screening questionnaires do not accurately identify patients at risk for OSA and do not rule out the presence of OSA in patients with CKD and ESRD. Consequently, objective cardiopulmonary monitoring is needed to reliably identify OSA in these populations.
Perspective:
It is unfortunate that these simple screening tools were not able to accurately identify patients at high risk for OSA, given the high prevalence of the condition in these populations. Further studies are necessary to validate more accurate screening strategies for OSA in CKD and ESRD patients. To minimize fluid status as a potential confounder, investigators chose to standardize studying ESRD patients after a nondialysis day. Given accumulation of fluid in the thorax and neck may influence episodes of apnea, additional studies may compare results in the ESRD population in relation to time they receive dialysis.
Keywords: Glaucoma, Kidney Failure, Chronic, Nephrology, Canada, Sleep Apnea Syndromes, Glaucoma Drainage Implants, Renal Dialysis, Renal Insufficiency, Body Mass Index, Berlin, Cardiology, Glomerular Filtration Rate, Sleep Apnea, Obstructive, Renal Insufficiency, Chronic
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