Journal of Clinical & Experimental Nephrology

Urinary Spot Urine Microalbumin/Creatinine Ratio is Not Significant When Compared with β-2 Microglobulin in Defining Tubular Proteinuria

Introduction: β-2 microglobulin is a costly but highly specific biomarker in determination of tubular proteinuria. In this study, we aimed to evaluate differentiation of tubular and glomerular proteinuria with comparing the urine β-2 microglobulin level and the spot urine microalbumin/total protein ratio.

Methods: Patients with proteinuria between the ages of 1 month and 18 years who applied to the Dr. Behçet Uz Children’s Hospital, pediatric nephrology clinic were included in our study. Patients with a spot urine total protein/creatinine ratio >0.2 mg/mg were included in the study. The urine microalbumin was studied using the spectrophotometric method in the Architect C-16000 device in the biochemistry laboratory of our clinic. The urine β-2M is measured by photometric method on the Architect C device. Urine samples for determination of the urine β-2M levels can be stored for 2 days at 2â?? to 8â?? and for 2 months frozen (-20°C). Spot urine total protein, microalbumin, creatinine and urine β-2 microglobulin levels were evaluated. Urine β-2M level >0.32 mg/L was accepted as the upper limit value for tubular proteinuria. Receiver Operating Characteristic (ROC) curve method and pearson correlation analysis was used for comparing spot urine total protein/ creatinine ratio, β-2 microglobulin and β-2 microglobulin/ creatinine ratio.

Results: Ninety-seven patients included in the study, 39 (40.2%) were female. The mean age was 10.2 ± 5.2 years. Glomerular and tubular proteinuria were found in 57 and 40 patients respectively. In patients with tubular proteinuria were spot urine microalbumin/total protein ratio 3.87 ± 2.80 mg/mg and β-2 microglobulin/creatinine ratio was 14.317 ± 23.787 mcg/g and glomerular proteinuria was 4.7 ± 3.0 mg/mg and β-2 microglobulin/creatinine 22.411 ± 32.231 mcg/g were determined. Pearson correlation analysis was showed no any correlation between values. ROC analysis for differentiation between glomerular and tubular proteinuria does not have any correlation between parameters also (area under curves 0.4).

Conclusion: There was no differences in spot urine microalbumin/creatinine ratio between glomerular and tubular proteinuria. Spot urine microalbumin/creatinine ratio was not useful for differentiation. Urine β-2 microglobulin and other known parameters is necessary for glomerular and tubular proteinuria.

Author(s): Eylem Tazegul Cokgezer* and Erkin Serdaroglu

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