Kidney disease screening needs rethink in hypertension

Apr 29 2013

By Eleanor McDermid, Senior medwireNews Reporter

The standard approach to detecting chronic kidney disease (CKD) fails to spot the condition in about a quarter of patients with hypertension, a study suggests.

The research also shows that tests that do detect the condition - cystatin C and albumin-to-creatinine ratio (ACR) - perform differently in people of different age groups and ethnicities.

"Taken together, our findings suggest that current CKD screening guidelines among hypertensive[s] may miss persons at risk," say lead study author Carmen Peralta (University of California, San Francisco, USA) and team. "Moreover, evaluation of improvement in CKD screening guidelines among hypertensives may require a targeted approach that incorporates demographic and clinical characteristics."

The study included 2088 participants from the 1988-1994 US National Health and Nutrition Examination Surveys and 737 from the 1999-2002 surveys. These participants had hypertension but not diabetes. The researchers excluded those with an estimated glomerular filtration rate (GFR) below 60 mL/min per 1.73m² based on serum creatinine, reasoning that such patients would have been identified as having CKD via routine tests, whereas the aim of this study was to assess the prevalence of occult CKD.

Among participants with a normal estimated GFR, 25% of those from the 1988-1994 surveys and 22% of those from the 1999-2002 surveys had occult CKD, according to their cystatin C or ACR results. These rates correspond to 17% and 16% of the US population, respectively, notes the team.

In the 1988-1994 sample, more participants had occult CKD according to ACR only (13%) than cystatin C only (8%) or both tests combined (3%). The capacity of the tests to detect CKD varied with age, with ACR detecting almost all cases in participants younger than 45 years, whereas cystatin C was required to detect about 10% of cases in those aged 65 years or older.

Also, cystatin C detected CKD most efficiently in White participants, whereas ACR detected most cases in Mexican-American participants, followed by Black participants.

The number needed to screen to identify one person with occult CKD was low, ranging from six to 12 depending on the test and the survey year, report Peralta et al in the Journal of Hypertension.

"Future studies are needed to understand whether targeted addition of cystatin C and ACR as screening tools for kidney end organ damage among hypertensives may be cost-effective in clinical practice," concludes the team.

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