A simple blood sample method for measuring oral zinc absorption in clinical practice.

Tracer activity in blood 14 days after the oral ingestion of zinc-65 has been compared with zinc absorption measured by whole-body counting in 10 controls and 25 subjects with Crohn's disease. Highly significant linear correlations (P less than 0.001) were obtained between blood tracer activity and zinc absorption for both the control group (previously reported) and the Crohn's disease group, thus allowing zinc absorption to be predicted from blood tracer activity with an accuracy of +/- 7.1% for the control group, +/- 17.1% for an active Crohn's disease sub-group and +/- 18.0% for a quiescent Crohn's disease sub-group. Relative to the whole-body counting method, the prediction of zinc absorption from blood tracer activity had a sensitivity of approximately 88%, a specificity of approximately 89% and an overall performance accuracy of approximately 88%. Therefore, where whole-body counting facilities are not available, the blood tracer technique for predicting zinc absorption could be a useful alternative.