Serum ionized magnesium in chronic alcoholism: is it really decreased?

Chronic alcoholism is associated with a marked deficit in total magnesium (tMg). However, little is known about the status of the physiologically active form, ionized magnesium (iMg). We assessed serum iMg (measured with two ion-selective electrodes, AVL 988-4 and NOVA CRT) and tMg concentrations in chronic alcoholics at admission (n = 31) and after abstinence (n = 13) and compared these results with those for a control group (n = 40). At admission, the tMg and NOVA iMg concentrations in alcoholics (0.78 +/- 0.020 and 0.38 +/- 0.016 mmol/L, respectively) were significantly less (P <0.001) than in the controls (0.85 +/- 0.008 and 0.50 +/- 0.006 mmol/L). The AVL iMg results, however, did not differ significantly between the two groups: 0.53 +/- 0.013 vs 0.56 +/- 0.006 mmol/L, respectively (P >0.05). The mean iMg between the two analyzers differed significantly in both groups (P <0.001). After 3 weeks of abstinence, the alcoholics showed a significant increase in tMg (P <0.001) and in both NOVA and AVL iMg values (P <0.01 for each). tMg concentrations were positively correlated with the AVL iMg values in both alcoholics and controls but correlated positively with the NOVA iMg results only in the controls. Thus, the altered status of iMg is instrument-dependent, and the usefulness of the measurement in alcoholics is yet to be determined.