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Podocyturia Is an Earlier Marker of Diabetic Nephropathy Than Microalbuminuria
Traditionally, the appearance of microalbuminuria has been used to detect the onset of diabetic nephropathy (DN), and its appearance prompts aggressive treatment.
However, podocyte injury starts to occur in previously assumed unaffected populations of patients before microalbuminuria appears, and therefore podocyturia is an earlier marker of DN than microalbuminuria, researchers stated here on April 15 at the National Kidney Foundation (NKF) 2010 Spring Clinical Meetings.
Shuchita Sharma, MD, Jacobi Medical Center, Bronx, New York, and colleagues established a test group of 12 patients with diabetes (9 with normoalbuminuria, 2 with microalbuminuria, and 1 with macroalbuminuria), and a control group of 9 healthy individuals.
Fresh urine was collected and urinary cell pellets were derived via centrifugation. Immunofluorescence was used to mark the presence of podocytes. The urinary podocytes were identified by colocalisation of podocyte-specific markers. The group also calculated podocytes-to-creatine ratios in order to semiquantify the cases of podocyturia.
As expected, urinary podocytes were not found in the healthy controls. However, all of the patients with diabetes -- including those with normoalbuminuria, who were considered to be "unaffected" by DN -- did have urinary podocytes in their urine test samples.
Mean podocyte-to-creatinine ratios for diabetic patients had a mean of 1,222.5 podocytes/mg creatinine, while the microalbuminuria group had a mean ratio of 119.3 podocytes/mg creatinine. As a result of these measurements, the team was able to determine that the degree of podocyturia does not correlate with the levels of albuminuria.
The unexpected aspect of the study, however, lies in the "significant podocyturia in normoalbuminuric diabetic patients," stated the researchers. "Thus, we believe that podocyturia is an earlier marker of DN than microalbuminuria."
Furthermore, podocyturia is likely a better predictor of progression since podocytes cannot regenerate once they have been lost.
The research group did note that the small size of the sample would require additional validation in a larger test group, and they plan to follow the initial groups prospectively to determine additional renal outcomes

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