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

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: evaluate two Ca++ analysers (Radiometer ICA1 (Copenhagen, Denmark) and Orion SS-20 (Orion Biomedical, Cambridge, Mass., USA) ); correlate serum ionised calcium, total calcium and albumin levels in various normal and pathological states; and 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). Reference normal values for Ca++ were established for healthy blacks, cord blood values being highest (mean 1.356 +/- 0.139 mmol/l) and adult values lowest (mean 1.159 +/- 0.04 mmol/l). Although the results obtained on the analysers were similar, the Radiometer ICA1 requires less blood and measures pH simultaneously. Correcting TCa for the variation in albumin within the normal range seemed to be of little value in assessing Ca++. The determination of TCa in most clinical situations is a good reflection of Ca++.

Congenital syphilis--who is at risk? A prevalence study at Baragwanath Hospital, Johannesburg, 1985-1986.

The prevalence of syphilis (or positive serology) in pregnant mothers delivering at Baragwanath Hospital, Johannesburg, was assessed in order to try to establish the prevalence of congenital syphilis and possibly to identify a specific population at risk. From August 1985 to January 1986 all mothers admitted to the major delivery wards were screened to determine whether they were booked or unbooked patients and whether they were seroreactive for syphilis. Infants of seropositive mothers were examined for clinical signs of congenital syphilis. A total of 9,071 patients were screened, 25% unbooked. The prevalence of mothers who had positive serological results with the rapid plasma reagin (RPR) test greater than or equal to 8 U was 1.8% in the booked patients opposed to 9.6% in the unbooked group (P less than 0.00001). During the study period 41 infected infants were found--23 symptomatic, 15 stillborn and 3 aborted fetuses. All these neonates were born to unbooked mothers and had positive RPR test results greater than or equal to 8 U. The results highlight the fact that congenital syphilis is still an important cause of infant morbidity and mortality and that the unbooked mother is at risk of having an affected offspring, especially when her RPR test is seroreactive greater than or equal to 8 U.