Faye and Payne estimated serum water from measuring chloride concentrations in serum and an ultrafiltrate of the serum. The concentration of chloride in the ultrafiltrate is the same as the chloride concentration in the diffusible water phase of the serum. The authors are from St. Jame's University Hospital in Leeds, England.



(1) chloride concentration in serum

(2) chloride concentration in an ultrafiltrate of the serum


serum water in percent =

= (chloride concentration in serum in mmol/L) / (chloride concentration in ultrafiltrate in mmol/L) * 100



• The chloride concentration was measured using a chloride meter (Corning-Eel 120), which I assume is ion specific. Measuring chloride by an indirect method on an autoanalyzer might give discrepant results, especially with hypertriglyceridemia or paraproteinemia.

• I assume that the ultrafiltrate will remove lipid and serum, giving close to 100% serum water.


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