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
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
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