A simple and inexpensive urine test routinely done in family doctors' offices may be the key to identifying individuals who are silently undergoing rapid kidney function decline, according to a study appearing in an upcoming issue of the Journal of the American Society Nephrology (JASN). Using this test could lead to potentially earlier and more effective treatments, lowering patients' risks of developing kidney failure and dying prematurely.
Approximately 60 million people globally have chronic kidney disease. Early detection and prevention of kidney disease is the only way to prevent kidney failure, but individuals with kidney disease often do not experience symptoms until later stages of the disease. Serial monitoring of kidney function in the general population would likely catch such silently progressing kidney disease early, but it would be too expensive.
William Clark, MD (University of Western Ontario and London Health Sciences Centre, in London, Canada) and his colleagues evaluated whether simple and routine screening tests for urine protein could be used to identify individuals at highest risk of rapid kidney function decline. These patients would benefit the most from serial kidney function monitoring and early treatments to prevent kidney failure.
The investigators followed 2,574 participants in a community-based clinic for an average of seven years. They found that a positive dipstick urine test (a protein concentration of ≥1g/L) was a strong predictor of rapid kidney function decline. Overall, 2.5% of participants in the study had a urinary protein concentration of ≥1g/L at the start of the study. If all of them were followed with serial monitoring of kidney function, one case of rapid kidney function decline would be identified for every 2.6 patients who were followed.
The test correctly identified whether or not individuals had rapid kidney function decline in 90.8% of participants, mislabeled 1.5% as having the condition, and missed 7.7% who were later identified as having the condition. Among those with certain risk factors (cardiovascular disease, age >60 years, diabetes, or hypertension), the probability of identifying rapid kidney function decline from serial kidney function measurements increased from 13% to 44% after incorporating a positive dipstick test.
"We showed that routine inexpensive urine dipstick screening in a population with and without risk factors will allow primary clinicians to follow fewer patients with serial monitoring to identify those with rapid kidney function decline that will potentially benefit from earlier referral and therapeutic intervention," said Dr. Clark.
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