Wr. Kulpmann et M. Gerlach, RELATIONSHIP BETWEEN IONIZED AND TOTAL MAGNESIUM IN SERUM, Scandinavian journal of clinical & laboratory investigation, 56, 1996, pp. 251-258
The relationship between the concentration of ionized magnesium and to
tal magnesium was investigated. Ionized magnesium was determined by an
ion-selective electrode (Microlyte 6, KONE) and the result was adjust
ed to pH 7.4. Total magnesium concentration was measured by flame atom
ic absorption spectrometry. Total and ionized magnesium were only clos
ely related in marked hypermagnesaemia (> 1.2 mmol/L), but correlation
was poor in samples with slightly elevated total concentration or in
hypomagnesaemia (< 0.65 mmol/L). The relationship was dependent on pro
tein concentration. The agreement between total and ionized magnesium
was acceptable in normoproteinaemia, but in hypoproteinaemia (< 40 g/L
) total magnesium concentration was classified in 35% of the samples a
s below or within the reference interval, whereas the pertinent ionize
d magnesium concentration was normal or elevated, instead. Studies on
paraproteinaemic sera clearly demonstrated that albumin concentration
is most important for the size of the protein bound fraction.