Analyte determination method and sensing assembly

A method comprising:

• providing a plurality of blood samples;
• providing, for each of the plurality of blood samples, a nonblood bodily secretion sample taken from a subject at a time of taking one of the plurality of blood samples from the subject, wherein each of the nonblood bodily secretion samples has a concentration of an analyte, the analyte being Na+, Cl−, H+, Ca2+, lactate, cortisol, urea, or creatinine, wherein the providing the nonblood bodily secretion sample comprises taking the nonblood bodily secretion sample from the subject's body over a given time period;
• determining, for each of the non-blood bodily secretion samples, a measure of an absolute amount of the analyte in the respective nonblood bodily secretion sample independently of any measurement of said concentration of the analyte in the respective nonblood bodily secretion sample;
• providing a measure of a blood concentration of the analyte in each of the blood samples;
• and
• determining a correlation between the measure of the absolute amount of the analyte and the blood concentration of the analyte using the determined measures of the absolute amount of the analyte in each of the nonblood bodily secretion samples and the determined measures of the blood concentration of the analyte in each of the blood samples.