Interpretation of urine sediment tests varies among nephrologists
Researchers observed substantial variability among nephrologists in their interpretations of findings from urine sediment examinations during kidney disease evaluations.
“Nephrologists often use their interpretation of a patient’s urine sediment to construct differential diagnoses and make decisions on whether to administer intravenous fluids, perform a kidney biopsy, initiate immunosuppressive therapy or provide only supportive care,” Ragnar Palsson, MD, of Brigham and Women’s Hospital in Boston, and colleagues wrote. “Given the commonly perceived importance of urine sediment examination in clinical decision-making, understanding variability in the urine sediment examination is important.”
After collecting urine samples from patients undergoing kidney biopsy, the researchers sent digital images and videos of urine sediment findings to nephrologists at 15 teaching hospitals in the United States. The nephrologists were asked to identify individual sediment findings and the most likely underlying disease process related to 10 different patients, totaling 76 study questions on casts and other individual features (eg, cells, lipid, bacteria or artifacts). The nephrologists received no other clinical information.
For casts, the researchers estimated overall percent agreement to be 59%. For other sediment findings, overall percent agreement was estimated to be 69%, with Fleiss estimates ranging from 0.13 for mixed cellular casts to 0.90 for squamous epithelial cells.
“Agreement ranged from slight for mixed cellular casts to almost perfect for squamous epithelial cells,” Palsson and colleagues elaborated. “For most sediment findings, moderate or substantial agreement was observed, as demonstrated by the overall estimates for casts and other sediment particles.”
According to the researchers, there were notable exceptions for certain findings that are “traditionally regarded as being of high clinical relevance during evaluation of patients with kidney disease.” These included variability in the interpretation of white blood cell casts, red blood cell casts and kidney tubular epithelial cells.
In a related press release, Sushrut S. Waikar, MD, chief of the section of nephrology at Boston Medical Center and a co-author on the study, commented on the utility of these findings.
“Ideally, the interpretation of the urine sediment should be the same when done by different doctors,” he said. “Our study provides important information that can be used to address these variabilities in order to create a better, more reliable test.”