Urine specific gravity as a diagnostic tool for dehydration in children

Background Using clinical judgment to diagnose dehydration can be highly subjective. To diagnose dehydration, it would be ideal diagnostic tool. In cases of dehydration, plasma osmolality rises, causing an increase in antidiuretic hormone (ADH) secretion. The increased ADH reduces urine production and increases urine osmolality. Previous studies have shown that urine osmolality specific gravity can be a reliable and objective determination of dehydration status. Objective To assess the accuracy of using urine specific gravity as a diagnostic tool to determine dehydration status of children with diarrhea. Methods We coducted the study in the pediatric ward of Sardjito Hospital from September 2009 to December 2009. Using a refractometer we measured urine specific gravity from patients with diarrhea. This measurement was then compared to a standard of acute body weight loss, with dehydration defined dehydration using specific gravity measurements was determined by a received-operator curve (ROC). Results Out of 61 pedients who werw recruited in this study, 18 (30%) had dehydration as defined by a body weight loss of 5% or more. Based on the ROC, we determind the cut-off value for urine specific gravity to be 1.022. Using this vallue, urine spcific gravity was 72% sensitive (95% CI 52 to 93), and 84% specific (95% CI 73 to 95) in determining dehydration status. Conclusion Urine specific gravity is less accurate than clinical judgment in determining dehydration status in children with diarrhea.