Clinical studies on ionized calcium using the radiometer ICA1 analyzer.

It is generally believed that measurement of ionized calcium in blood should more clearly reflect changes in calcium metabolism than measurements of total calcium concentration. We have investigated ionized calcium levels using the Radiometer ICA1 Analyzer in number of clinical situations where total calcium, hydrogen ion or protein concentrations are abnormal. While there are a number of clearcut situations in which ionized calcium measurements are superior to total calcium, it is apparent that chemical activity of calcium ions in blood may sometimes not reflect their physiological activity. In addition, the problem of clinical interpretation of ionized calcium levels found in patients with extreme disorders of acid-base balance or of plasma protein concentration remains to be resolved. The role of ionized calcium measurement in routine clinical chemistry will be discussed.