Results

Two hundred and fifteen measurements of free (ionic) and total calcium were performed on sera from 184 patients in whom some disturbance in cal-cium metabolism was suspected. The correlation Coefficient between free and total calcium was 0.94, but a scattergram indicated that free calcium con-centration cannot be predicted from knowledge of total calcium concentration. In “normal ” individuals the correlation coefficient was only 0.45. Homeosta-sis of free and total calcium was examined by mak-ing periodic measurements in seven normal individu-als over a period of eight months; the variability around the individual’s mean value was 1.2 % for free calcium and 1.9 % for total calcium. Free calcium, as properly measured by the ion-specific electrode, is a better measure of calcium status than is total calcium in the disease states studied, which were mostly hyperparathyroidism, multiple myeloma, and renal failure. Additional Keyphrases: diagnostic acid #{149}parathyroid hormon