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The newspaper of The Johns Hopkins University February 9, 2004 | Vol. 33 No. 21
Early ID of Kidney Disease Cost-Effective Only When Directed

By Karen Blum
Johns Hopkins Medicine

Routine annual testing for abnormally high levels of protein in the urine — an early marker of kidney malfunction and premature death — should be limited to those with other risk factors and older Americans, a Johns Hopkins study indicates.

"Given the relatively inexpensive and safe nature of urine testing for proteinuria, physicians might assume that frequent screening is something worth doing for everyone, but that's probably not true," said L. Ebony Boulware, lead study author and assistant professor of medicine at Johns Hopkins. "Our results show that for the majority of the U.S. population — those without hypertension or diabetes — annual screening can actually be quite costly and anxiety-producing for patients if you factor in false positive or negative test results and the subsequent tests they may require. Screening should be directed at people with substantial risk of developing kidney disease, or it should be performed on a less frequent basis, such as every 10 years."

In the Hopkins report, published in the Dec. 17, 2003, issue of the Journal of the American Medical Association, the investigators recommend that annual screening be limited to hypertensive patients age 30 and up, and adults age 60 and up.

Chronic kidney disease is a growing public health problem that contributes to high health care costs, the authors note. More than 10 million Americans have some kidney damage, and more than 300,000 Americans have end-stage renal disease, a number estimated to double by 2010. With no set guidelines for the urine screening test, physicians have varied in whether and how they check patients for early kidney disease.

"Patients should be aware of their potential risk of kidney disease and ask their physicians if they should be tested, particularly if they have diabetes or hypertension, or are at least age 60," said senior study author Neil R. Powe, director of Johns Hopkins' Welch Center for Prevention, Epidemiology and Clinical Research. "Physicians should understand which patients warrant periodic testing and subsequent treatment."

Boulware, Powe and colleagues assembled population data from the third National Health and Nutrition Examination Survey, known as NHANES III, and death statistics from a national mortality data file, then used that information to develop a computer program comparing the effectiveness of annual screening — or no screening — for proteinuria at different yearly intervals among hypothetical groups of healthy individuals and those with hypertension.

The screening strategy consisted of a urine test for proteinuria during an annual visit with a primary care physician. If results were positive, patients visited their doctor again for further testing and, if necessary, were referred to a kidney specialist or were prescribed medications such as angiotensin-converting enzyme inhibitors or angiotensin II-receptor blockers to slow the progression of kidney disease and lower the incidence of heart attacks and other problems.

In the no-screening strategy, patients did not undergo routine screenings, but those who had natural progression of kidney disease may have been screened by their physicians as symptoms occurred. Screening of all study patients occurred annually until age 75, or until they developed end-stage renal disease or died.

The research team's analysis found that to save one year of "high-quality" life (called a "quality-adjusted life-year" or QALY) among the general population would cost $282,818. Ratios of $50,000 to $100,000 per QALY are thought to be more reasonable in decisions about mass screening. Screening everyone resulted in 135 invasive kidney biopsies, seven complications from biopsies and complication costs of $9,116, but the prevention of only one new case of end-stage renal disease and seven deaths per 1 million people per year.

However, for those with hypertension, screening proved highly favorable, at a cost of $18,621 per QALY. Such screening resulted in 196 kidney biopsies, seven complications from biopsies and complication costs of $200,000, with the prevention of approximately 14 new cases of end-stage renal disease and 104 deaths per million people per year.

"Physicians must incorporate a variety of considerations into decisions regarding early disease detection," Boulware said. "When taking into account the kidney disease-slowing benefits for people with neither hypertension nor diabetes, who have low incidence and prevalence of proteinuria, regular screening averts very few ESRD cases and prevents few deaths. The resulting minimal gain in QALYs is too small to balance the costs of such testing."

The study also found that urine protein testing in the general population became more cost-effective when annual screening was initiated at age 60, at a cost of $53,372 per QALY. In addition, screening also made financial sense when done every 10 years. The estimated costs were $80,700 per QALY at age 50, $6,195 per QALY at age 60 and $5,486 per QALY at age 70.

Continuing research will use the computer program to look at the cost-effectiveness of screening other populations, such as African-Americans (who have high rates of hypertension and diabetes), and to study other factors in kidney disease management, Boulware said.

The study was supported by the National Kidney Foundation of Maryland; the National Institute of Diabetes and Digestive and Kidney Diseases; and the Robert Wood Johnson Minority Faculty Development Program. Co-authors were Bernard G. Jaar, Michelle E. Tarver-Carr and Frederick L. Brancati.


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