At-home Testing of Blood Sodium for Management of Diabetes Insipidus

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PROJECT SUMMARY/ABSTRACT Central diabetes insipidus (DI), caused by a deficiency of the hormone vasopressin, is a rare disease that affects 1 in 25,000 individuals. Individuals who lack vasopressin can quickly have high sodium levels and are vulnerable to dangerous dehydration, leading to frequent hospitalizations. Treatment for DI includes pharmacologic vasopressin replacement and careful regulation of fluid intake. While under-treatment of DI causes hypernatremia (high blood sodium levels) and dehydration, over-treatment causes hyponatremia (low blood sodium levels), which can lead to seizures, permanent neurological injury, multi-system organ impairment, and even death. The most substantial barrier to optimal DI management, and to preventing complications and hospitalizations, is the lack of readily available, quick, and accurate blood sodium measurements. Individuals with severe DI travel to hospitals frequently and the delay in return of sodium levels due to unavailability of rapid tests leads to preventable complications from mismanagement of DI. There is therefore a substantial unmet need for in-home sodium monitoring in the target pediatric DI population as well as an exciting potential of a sodium monitor specifically designed and approved for in-home use. Currently available blood electrolyte analyzers are expensive laboratory instruments, accept venous blood at volumes much higher than fingersticks, and are not practical for routine in home testing for blood sodium. The overall goal of this program is to develop an in-home, cost-effective sensor product that accurately measures blood sodium. A rapid and simple electrochemical test to quantify the blood levels of sodium meets a critical need within DI care. Giner will develop a handheld blood sodium monitor and demonstrate quantitative detection of sodium using small volume fingerstick blood volumes (< 100 µl), within a broad linear range of 100-360 mM (normal range is 138-146 mM). Giner will utilize a modified ion-selective electrode (ISE) approach that will allow for rapid (single-step), label-free, and reagent-free operation similar to a blood glucose test. The Aims of the Phase I feasibility program are: 1) Development of a sodium test strip modified with sodium ion selective membrane (ISM) formulations; 2) Development of sample handling techniques and sensor calibration for point-of-care operation; and 3) Adapting sensor for blood analysis, testing with blood plasma samples, and benchmarking performance against the standard clinical chemistry methodologies.