THURSDAY, Jan. 29 (HealthDay News) -- The widely used method of estimating glomerular filtration (eGFR) rates from routine blood work may not be a cost-effective way to identify people with chronic kidney disease, U.S. researchers report.

The test indicates the volume of blood filtered by the kidneys over time, and its formula factors in measures of serum creatinine, age, gender, height and weight. Poorly functioning kidneys are less able to filter the molecule creatinine, resulting in higher serum creatinine levels.

In this study, Dr. Harold Feldman, of the University of Pennsylvania School of Medicine, and colleagues compared eGFR with serum creatinine reporting alone, another commonly used measure of kidney function. The researchers used published data to create a hypothetical group of 60-year-old people having annual blood tests for 18 years.

Their initial analysis showed that reporting eGFR was more effective than reporting serum creatinine. Among 10,000 people, eGFR reporting would have led to an average of 13 fewer deaths and 29 fewer cases of end-stage kidney disease than serum creatinine reporting.

While measuring eGFR would likely reveal a number of patients with undiagnosed kidney disease, the test also would incorrectly make a preliminary diagnosis of kidney disease among many people without kidney problems, the researchers said.

They estimated that eGFR would generate 11,348 more false positive kidney disease cases than serum creatinine reporting. False positive results can lead to increased costs for additional clinical tests and potentially reduce a person's quality of life.

The study was published in the February issue of the Clinical Journal of the American Society of Nephrology.

"Despite the widespread enthusiasm and increasing adoption of routine estimated glomerular filtration rate reporting, our study shows that clinicians and policymakers should carefully examine the consequences of this practice," Feldman and colleagues, said in a journal news release.

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