Laying the foundation for enhancing safety of desmopressin in older people: Validation of capillary blood sodium levels.

Purpose: We aim to make desmopressin a safe treatment option for (older) patients at risk for hyponatremia, by introducing a new way of sodium monitoring. The goal is to reduce the risk of hyponatremia, enhance patient safety and ultimately introduce self‐monitoring of sodium levels. The first step in the aforementioned is to validate capillary sodium. Materials and Methods: 100 randomly selected patients admitted to the urology department received a single finger prick to collect capillary blood (250 µl) in a lithium‐heparin tube. Each patient acted as its own control for the capillary and venous blood sample. Venous and capillary plasma sodium were analyzed by indirect ion‐selective electrode measurement. The primary outcome was the agreement between capillary and venous sodium measurements, measured by the intra‐class correlation coefficient (ICC). Results: One hundred paired blood samples were obtained of which four were excluded. There was no significant statistical difference observed between venous and capillary sodium (−0.23 mmol/L, p = 0.374). The ICC for single measures between capillary and venous sodium was 0.82 (95% confidence interval 0.75–0.88). Inter‐method differences analyzed by a Bland–Altman plot and a Passing–Bablock regression did not reveal a statistically significant difference between both groups. Conclusions: We demonstrated that venous and capillary sodium levels are interchangeable, taken into account the inter‐ and intravariability between analyses. We provided the first step towards a simple and safe solution for frequent sodium monitoring through a minimal invasive capillary blood collection. The results are of direct clinical relevance to safely use desmopressin in (older) patients at risk. [ABSTRACT FROM AUTHOR]