A comparative study of two methods of measurement of fractional calcium absorption: results in normal individuals and patients with various disturbances of calcium metabolism.

Two methods of measurement of fractional calcium absorption have been compared in the same individuals. There is a significant correlation between fractional 47Ca absorption as measured with a blood counting method and with an external counting method after intravenous and oral administration of 47Ca (P less than 0.001). Two varieties of the external counting method, namely with intervals of 2 h and 7 days between the i.v. and oral doses, have been compared. In a group of twenty-one patients with chronic renal failure (not on haemodialysis), 47Ca absorption as measured by external counting was significantly lower than in the control group (P less than 0.001). When put on a dialysis programme a group of six patients showed a significant increase of the fractional 47Ca absorption (P less than 0.01).