METHOD AND APPARATUS FOR DETERMINING INTERSTITIAL VOLUME

A method and system for selecting a treatment for a subject based on a value for the interstitial space volume of the subject utilizes plurality of sample data values representing concentrations of small and large markers in plurality of blood samples over time. The sample concentrations are utilized to predict a hypothetical peak concentration of the small marker prior to the dissipation of the markers during the test period. This hypothetical peak concentration and other sample values are utilized with either a bi-exponential or tri-exponential decay curve fitting algorithm to define a decay curve, the curve characteristics of which are then utilized to calculate values for glomerular filtration rate, a leakage rate of the small marker into interstitial space, and finally a value for the interstitial volume. The determined value for the interstitial volume can then be compared with number thresholds and decisions made for recommended therapy for the subject, if desired.