Despite the fact that albuminuria represents a key risk factor for chronic kidney disease (CKD), even in the absence of reduced filtration, testing for the condition is low among adult patients with diabetes and is even lower among those with hypertension, suggesting commonly missed opportunities for CKD detection and treatment, a new study shows.
“In this national cohort study of US adults at risk for CKD, we estimated that approximately two-thirds of persons with albuminuria have not been identified by urine albumin-creatinine ratio [UACR] testing,” the authors report in research published in JAMA Network Open.
“Early identification of albuminuria is increasingly crucial given the growing number of therapies, such as sodium-glucose cotransporter 2 inhibitors (SGLT2i) and nonsteroidal mineralocorticoid antagonists, that have been shown to slow the progression of CKD and prevent cardiovascular complications,” the authors add.
Key factors for diagnosing CKD include either reduced filtration, defined as an estimated glomerular filtration rate [eGFR] of <60 mL/min/1.73 m2, or albuminuria, defined as UACR >30 mg/g. However, while the vast majority of patients with hypertension or diabetes ― approximately 90% ― undergo eGFR testing, the rate for albuminuria testing is much lower.
Among those with diabetes, albuminuria testing is consistently reported at 50% or less across a variety of settings, despite being recommended in most guidelines. And among those with hypertension without diabetes, albuminuria testing rates are much lower, at only about 10%.
As many as 40% of people with CKD have albuminuria but normal eGFR, meaning their condition can go undetected if they are only tested for eGFR.
Detection is especially important because albuminuria ― regardless of eGFR status ― increases the risk of cardiovascular events, CKD progression, and mortality.
To investigate the extent of underdetection of albuminuria, researchers identified 192,108 patients in National Health and Nutrition Examination Surveys (NHANES) from 2007 to 2018. They then applied the albuminuria estimation model to electronic health records of active outpatients with hypertension or diabetes from January 2017 to December 2018, including those who had been tested for albuminuria and those who had not been tested.
Of the patients, 96.6% had hypertension, and 26.2% had diabetes. The mean eGFR was 84 mL/min/1.73m2.
Overall, only 17.5% (33,629 patients) had undergone albuminuria testing. Among those patients, 34.3% had albuminuria, according to the model.
Of the 158,479 who were not tested, the estimated albuminuria prevalence rate was 13.4%, meaning that only 35.2% of the projected population with albuminuria had been tested.
The lowest testing rates were among people with hypertension who did not have diabetes. Of those patients, only 5% underwent albuminuria testing, which detected only 10% of cases of albuminuria in this population.
Those who had been tested for albuminuria were more likely to have received a prescription for an angiotensin-converting enzyme inhibitor, an angiotensin II receptor blocker (OR, 2.39), or an SGLT2i (OR, 8.22), and they were also more likely to have blood pressure of less than 140/90 mm Hg (OR, 1.20).
“These results suggest that underutilization of UACR represents a major barrier to diagnosis of CKD and deployment of therapies to prevent CKD progression and the associated cardiovascular risk,” the authors note.
Reasons for Inadequate Albuminuria Testing
Key reasons for the low rates of albuminuria testing could be that guidelines do not adequately emphasize such testing and that there is a lack of awareness of the need to take simple extra steps, first author Chi D. Chu, MD, of the Department of Medicine, University of California, San Francisco, told Medscape Medical News.
“I think the key contributors are lack of specific guidelines recommending whom to test and when and/or how often to test, and accompanying implementation efforts, the need for a urine sample, and inconsistent lab/ordering nomenclature,” Chu said.
Furthermore, while guidelines from the nonprofit organization Kidney Disease: Improving Global Outcomes (KDIGO) recommend staging CKD by both eGFR and albuminuria, the latter is often omitted.
“Oftentimes, CKD is operationally defined solely as eGFR <60 in research and in other clinical practice guidelines,” Chu noted.
Reduced eGFR is often detected incidentally.
“Most of the time, eGFR is part of a lab panel that is not drawn specifically for assessing kidney health and identifying modifiable risk factors,” Chu added.
Overall, given the well-documented low rates of testing, “our results estimating that a large fraction of albuminuria was undetected was not surprising,” Chu said.
“The take home-message is that for people with risk factors for kidney disease, both albuminuria and eGFR are key parts of assessing kidney health and risk, as well as identifying those who would benefit from treatment,” Chu added.
The study was supported through a collaborative agreement with Bayer Inc. Chu is supported by the Agency for Healthcare Research and Quality and the National Center for Advancing Translational Sciences of the National Institutes of Health.
JAMA Netw Open. Published July 27, 2023. Full text
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