How does OSA present clinically in patients with CKD, and is OSA clinically apparent in this population? Nicholl et al49 evaluated 119 patients with CKD and compared those with and without OSA using a sleep history questionnaire, the Epworth Sleepiness Scale and the PSQI. Sleep apnea was determined by type 3 portable monitoring, with an RDI ≥ 15 considered diagnostic of OSA. The prevalence of OSA symptoms (snoring, witnessed apnea, and unrefreshing sleep) and PSQI scores did not differ between patients with CKD with OSA and patients with CKD without apnea. The prevalence of daytime sleepiness (reflected by an Epworth Sleepiness Scale score of > 10) was higher in patients with CKD with OSA than in patients with CKD without apnea (39% vs 19%, P = .033). However, both daytime sleepiness and symptoms of sleep apnea outlined previously were considerably less frequent than in patients with OSA without a history of kidney disease. Consequently, many patients with CKD can have OSA without the typical symptoms of this disorder. The investigators concluded that the presence of OSA in patients with CKD is unlikely to be clinically apparent and that objective nocturnal monitoring is required to reliably identify this comorbidity. The same authors evaluated three common screening questionnaires for OSA in patients with CKD, namely, the Berlin questionnaire, adjusted neck circumference, and the STOP-BANG (snoring, tiredness during daytime, observed apnea, high BP, BMI, age, neck circumference, sex) questionnaire.50 This study included patients with CKD (n = 109) and ESKD (n = 63). OSA was present in 38% of patients with CKD and 51% of those with ESKD. All screening instruments had a satisfactory sensitivity (56%-94%) but poor specificity (29%-77%) and low accuracy (51%-69%) in both patients with CKD and those with ESKD with sleep apnea (RDI ≥ 15). Accuracy was defined as the total number of correct risk assessments divided by the total number of risk assessments. The results were unchanged if a more conservative RDI (RDI ≥ 30) was used to define sleep apnea. The authors concluded that current screening questionnaires for OSA do not accurately identify patients at risk for OSA or rule out the presence of OSA in patients with CKD (and ESKD). Based on this literature, it appears that patients with CKD have a high prevalence of sleep-related complaints, but their clinical presentation is not specific enough to reliably identify those who have sleep apnea.