Establishing Urinary NT-ProBNP as a Pain-Free Monitoring Tool in Children with Congenital Heart Disease

Objectives: Natriuretic peptides and especially BNP and NT-ProBNP have been established as useful markers for cardiac function in children with congenital heart disease and have a widespread clinical use. The significance of natriuretic peptides in the evaluation of children and adults before and after cardiac surgery has been established in multiple studies. To our knowledge, there has been no investigations showing the correlation of urinary and plasma NT-ProBNP values in children with congenital heart disease. Establishing urinary biomarkers is important for children because blood sampling is more traumatic and often more difficult especially in small children. In this study, we investigated blood and urine samples of children who were about to undergo cardiac surgery to show the correlation between blood and urine values.

Methods: We investigated 33 coupled samples from children before undergoing cardiac surgery aged between 1 day and 3 years (median 119 days) with all kinds of congenital heart defects. Blood samples were collected during the routine preoperative blood draw. At the same time, a urine collection bag was placed, and a sample of 2 to 10 mL was collected for investigation. All samples were aliquoted and stored at −80°C. NT-ProBNP was determined using the Elecsys proBNP II assay for blood and urine samples.

Results: In this study, 33 coupled samples of plasma and urine in children with congenital heart disease were analyzed. The plasma NT-ProBNP values varied between 68.4 and 67,597 pg/mL with a median of 2,165 pg/mL. The urine NT-ProBNP values varied between 5.83 and 70,000 pg/mL with a median of 125 pg/mL. A Pearson’s correlation between plasma and urine values of NT-ProBNP showed a correlation coefficient of 0.82 (p < 0.000). Interestingly, there is no better correlation with the quotient of NT-ProBNP in urine and the creatinine level in urine (correlation coefficient of 0.80 with p < 0.000). Analyzing the linear regression of these two parameters showed a R ² value of 0.67. This would suggest that the urinary NT-ProBNP can be established as a marker in children with congenital heart disease.

Conclusion: Urinary NT-ProBNP values correlate well with plasma NT-ProBNP. A widespread implementation of urine biomarkers could help reduce the need of blood sampling in this, sometimes very traumatized group of children.