Many diagnostic tests for investigating acute kidney injury (AKI) have limited clinical utility, even when results are positive or abnormal, a new study found.

“In particular, selected urine and blood tests are unlikely to impact AKI diagnosis or management,” investigators led by David E. Leaf, MD, of Brigham and Women’s Hospital in Boston, and colleagues reported online in BMC Nephrology.

In addition, the study found that the frequency of testing increases with higher AKI stages for nearly all diagnostic tests.

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Dr. Leaf and his colleagues characterized AKI diagnostic testing among 4,903 adult in-patients who experienced 5,731 AKI episodes, assessing the frequency of testing and the frequency of abnormal test results overall and by AKI stage.

The most commonly ordered tests were urinalysis and automated urine sediment examination. A sensitivity analysis evaluated the appropriateness of testing and diagnostic yield of selected glomerulonephritis tests and paraproteinemia tests in a random subcohort of 100 patients (50 each). Using prespecified criteria, the investigators concluded that glomerulonephritis and paraproteinemia testing was appropriate in 50% and 54% of tests, respectively.

Among patients who had a glomerulonephritis test, results were normal in 45 (90%) out of 50 tests. Results affected AKI diagnosis or management in only 1 (2.2%) of the normal tests and none of abnormal tests). For patients who had a paraproteinemia test, testing was normal in 39 (78%) of 50 tests. Results affected AKI diagnosis or management in none of the normal tests and in 4 of the abnormal tests.

Clinicians ordered urine eosinophil tests in 7% of AKI episodes (3%, 9%, and 24% among patients with AKI stages 1, 2, and 3, respectively), with abnormal results detected in 7% of those tests. Clinicians ordered serum protein electrophoresis tests in 6% of all AKI episodes—with abnormal results found in 19% of those tests—and anti-neutrophil cytoplasmic antibody testing in 3% of AKI episodes, with abnormal results found in 11%.

Renal ultrasound was performed in 567 AKI episodes (10%), and abnormal results were detected in 196 (35%) of tests. Hydronephrosis was detected in 109 tests (19%); of these, 35 (32%) resulted in a procedural intervention.

Computerized tomography of the pelvis/abdomen (CTAP) was ordered in 54 AKI episodes (0.9%), with abnormal results detected in 18 (33%) of the scans. Among the abnormal tests, 61% resulted in an intervention. CTAP was more likely than renal ultrasonography to show abnormalities among patients with higher AKI stages.

The authors stated that “development of better diagnostic tests that provide reliable and actionable data on AKI diagnosis and management should be a priority in AKI research. “The dearth of such tests may be a key reason why therapeutic advances to improve outcomes in AKI have been largely unsuccessful.”