One-hour test for estimating intestinal absorption of calcium by using stable strontium as a marker.

Intestinal absorption of calcium is a relevant marker in a broad spectrum of diseases; however, its determination in clinical practice is difficult. Our aim was to design a simple test for this based on stable strontium (88Sr). The correlation between the intestinal absorption of simultaneously administered 45Ca and 88Sr was investigated in patients with various disorders of the bone and calcium metabolism. The area under the curve for the period 0-60 min after dosing (AUC0-60 in mmol.L-1.min), being a representative measure of intestinal absorption, showed a close correlation between both elements (r = 0.90, P < 0.001). Moreover, the measure of agreement in classifying the patients as low, intermediate, or high absorbers was high (kappa = 0.80). We conclude that a test based on measuring AUC0-60 of strontium is a fast and inexpensive way to obtain reliable information about the level of intestinal calcium absorption.