Objectives: Hypertension guidelines recommend screening for chronic kidney disease (CKD) using serum creatinine and urine dipstick; this strategy may lead to misclassification. Persons with occult CKD [i.e. missed by creatinine but detected by cystatin C or albumin-to-creatinine ratio (ACR)] have higher risks for death, cardiovascular events, and end-stage renal disease.
Methods: We studied occult CKD prevalence among nondiabetic, hypertensive adults in National Health and Nutrition Examination Survey 1988-1994 (N = 2088) and 1999-2002 (N = 737). We defined occult CKD as estimated glomerular filtration rate by cystatin C (eGFRcys) less than 60 ml/min per 1.73 m and/or ACR at least 30 mg/g among persons with eGFRcreat more than 60 ml/min per 1.73 m. We studied occult CKD prevalence by either marker, stratified by age, race/ethnicity, and assessed clinical predictors associated with occult CKD presence.
Results: In 1988-1994, occult CKD was prevalent among 25% of nondiabetic hypertensive persons, and it was 22% in 1999-2002. Each marker's ability to detect occult CKD varied by age and race. Cystatin C detected occult CKD among 8.9% of persons more than 65 years, and among 3.8% of whites. ACR detected occult CKD among 9.3% of persons less than 45 years, 16.6% of Blacks, and 20.6% of Mexican-Americans. In multivariate models, each decade of advancing age was associated with a higher occult CKD prevalence by cystatin C (OR 3.1, 95% CI 2.5-3.8) in 1988-1994 and 1999-2002 (OR 2.9, 1.8-4.6).
Conclusion: Current hypertension guidelines may fail to detect a large proportion of high-risk individuals with CKD who can be identified by cystatin C or ACR. Future studies are needed to evaluate targeted use of multimarker renal panels among hypertensives.