Interference of haemolysis and hyperproteinemia on Sodium, Potassium, and Chloride measurements in canine serum samples.

The exact measurement of Sodium (Na+), Potassium (K+), and Chloride (Cl−) ion concentrations in serum samples is important for correct diagnosis and therapy, and a knowledge of the interference factors which influence the analytic method used, ensures correct reading of laboratory data (Di Bartola et al. 1999). Serum haemolysis may cause pseudohyperkaliemia in humans (Miseta et al. 1992), in some breeds of dog (Akitas) having high K+ concentration in erythrocytes (Green 1996), and in new-born puppies (Berry et al.1991); furthermore it may cause pseudohypochloremia by haematic dilution. Hyperproteinemia may cause both pseudohyponatremia (Coulter and Small 1972; Faye and Payne 1986; Degen 1987; Burnett et al. 1988; Di Bartola et al. 1999) and pseudohypochloremia (Di Bartola et al. 1999). The analytical methods normally utilized for electrolyte determinations are: flame photometry (FF) (Araneo 1972), indirect or direct ion-selective electrodes (ISE) (Oesch et al. 1986), and enzymatic spectrophotometry (ES) (Berry et al.1991). The aim of this study is to evaluate, in canine serum samples, both the interference of haemolysis and hyperproteinemia on measurement of Na+, K+, and Cl− concentrations with flame photometry, indirect ISE, and enzymatic spectrophotometry, and to ascertain which of these three methods is more sensitive to the two kinds of interference studied.