(Original Article) Optimizing Urine Volume for Chemical Analysis and Microscopic Examination in Pediatric Patients

Abstract

The standard urine volume required for routine urinalysis is approximately 10 mL. However, in pediatric patients, especially neonates at the Queen Sirikit National Institute of Child Health, collecting this volume can be difficult. This study aimed to determine the minimum urine volume that allows reliable results for both chemical analysis and microscopic examination. Urine specimens from 50 pediatric patients were analyzed at volumes of 0.5, 1.0, and 5.0 mL and compared with the standard 10 mL. Chemical analysis of ten routine parameters showed overall agreement exceeding 80% across all reduced volumes. Specific gravity demonstrated strong correlations with the standard volume, with Pearson’s correlation coefficients (R) of 0.907, 0.950, and 0.979 for 0.5, 1.0, and 5.0 mL, respectively. Microscopic examination revealed that samples of 0.5 mL and 1.0 mL showed significantly different counts of red blood cells and white blood cells compared with 10 mL (p < 0.05), with poor agreement (k = 0.042-0.056). Other sediment components—including cellular casts, squamous epithelial cells, mucus, bacteria, crystals, amorphous material, and yeast—demonstrated fair to moderate agreement (k = 0.220-0.481). In contrast, the 5.0 mL samples showed very good agreement with the standard 10 mL (k = 0.858-1.000). In conclusion, a urine volume as low as 0.5 mL is adequate for chemical urinalysis, while at least 5.0 mL is recommended for microscopic examination. When volumes below 5.0 mL have to be used, the tested volume should be clearly reported in laboratory results.