Comparison of two calcium analysers, African blacks commercial ionised and values in South

Summary Although research on the ionised fraction of serum calcium (Ca) started some 50 years ago, normal values and, above all, the methods of determination are still controversial. The use of calcium ion selective electrodes greatly enhanced and improved the measurement of Ca++. A study was carried out to: (I) evaluate two Ca++ analysers (Radiometer ICA1 (Copenhagen, Denmark) and Orion SS-20 (Orion Biomedical, Cambridge, Mass., USA»; (iI) correlate serum ionised calcium, total calcium and albumin levels in various normal and pathological states; and (iil) determine the values of Ca++ in healthy black subjects. The two analysers ·gave results showing very good correlation over a wide range (r = 0,986). Results for ionised Ca++ v. total calcium (TCa) showed a significant linear correlation (r = 0,956). Correcting TCa for variations in serum albumin concentrations did not improve this correlation (r = 0,9114). Refer­ ence normal values for Ca++ were established for healthy blacks, cord blood values being highest (mean 1,356 ± 0,139 mmol/I) and adult values lowest