Study on correlation of urine specific gravity with other laboratory parameters of urine in children with Nephrotic syndrome

Abstract

Nephrotic syndrome is a frequent childhood kidney disease in which proteinuria is a significant characteristic. Proteinuria can be a benign condition as well as indicates severe underlying renal or systemic diseases. The variation in the prevalence of proteinuria may occur based on the definition used or the evaluation time of the test. Proteinuria is present in up to 10% of routine urine testing in school-aged children, although this decreases to 0.1% with repeated testing. The study aimed to analyze the correlation of urinary specific gravity with other laboratory parameters of urine in children with nephrotic syndrome. Methods: This cross-sectional study was conducted in the Department of Pediatric Nephrology (NIKDU), Dhaka from October 2019 to June 2021, and a total of 153 patients with nephrotic syndrome were enrolled after taking written consent. Urine samples were collected for both 24 hours and spot for estimation of urinary protein, urinary creatinine, dipstick protein, and specific gravity by dipstick method. Spot urinary Protein Creatinine Ratio (PCR) and 24 hours urinary protein were also estimated. Results: Among 153 study subjects maximum (44.4%) were 2-5 years old followed by 58 (37.9%) who were 5-10 years and 27 (17.6%) were >10 years old. Boys (61.4%) were more predominant than girls (38.6%). Mean 24 hours urinary volume was 1097.78±662.63 ml, 24 hours urinary creatinine was 32.17±23.70 mg/dl, 24 hours urinary total protein was 851.42±123.68 mg/dl, 24 hours urinary total protein (UTP) was 7.52±7.65 gm/m2/24 hours urinary specific gravity 1.020±0.02, spot urinary protein 989.49±1136.73 mg/dl, spot urinary creatinine was46.09±43.73 mg/dl, spot urinary PCR was 21.87±18.24 mg/mg and spot urinary specific gravity was 1.020±0.01. The Scatter diagram showed a significant positive correlation of 24 hours urinary specific gravity with 24 hours urinary protein (r=0.169, p=0.037). There was a significant positive correlation of 24 hours specific gravity with 24 hours urinary creatinine (r=0.380, p=<0.001). There was a significant positive correlation of spot urinary protein with spot urinary specific gravity as well (r=0.206, p=0.011). Spot urinary specific gravity showed a significant positive correlation with spot urinary creatinine (r=0.355, p=<0.001). There was a significant negative correlation of spot urinary specific gravity with spot urinary PCR (r= -305, p=<0.001). Conclusion: It can be concluded that urinary specific gravity had a substantial correlation with other laboratory parameters of urine and can be used as an important diagnostic tool for diagnosing proteinuria in children with nephrotic syndrome