Automated serological technique with special emphasis on a solid phase test for red cell antibody detection in routine blood banking

Automated serological techniques for erythrocyte antigen typing and antibody screening are presented and evaluated in a larger number of samples and throughout routine processing. Both techniques are microplate-adapted with computerised sample identification, sample and reagent dispensing, and interpretation of results. The method described for typing of the RBC antigens K, Fya, and C, c, E, e compared well to the manual haernagglutination test. The concurrence was >= 99.4 % with an editing rate of 5.5% vs. 0.8%. It was also evaluated for routine phenotyping of blood donor samples and it proved to be suitable for this purpose.

Previously described solid phase adherence assays (SPH) were modified to permit preparation and storage of polystyrene microplates in an automated routine for RBC antibody screening of approximately 40,000 samples per year from pregnant women, patients and blood donors. In comparison to the AutoAnalyzer (AA) method, the SPH-IAT (indirect antiglobulin) and SPH-ENZ (enzyme-enhanced) tests were more specific, with a significant reduction in positive screened samples, as well as in non-specific or negative reactions after further investigations.

The SPH test was used for RBC antibody screening a total of 123,246 samples from pregnant women, patients and blood donors from October 1992 to July 1993 and January 1996 to June 1998. Alloantibodies were detected in 0.25% of pregnant women samples, in 0.30% of patient samples and in 0.28% of blood donor samples. Anti-D, anti-E, anti-K, anti-Fya and anti-c were the most frequently encountered antibodies of clinical significance in the sample material as a whole.

The maternal health care programme in Stockholm was evaluated clinically in a retrospective study of approximately 38,700 infants born in Stockholm August 1992 through February 1994. We found no need to test Rh(D) positive women more than once during each pregnancy, even if done as early as at 8-10 weeks of gestation. All maternal immunisations, which made it necessary to give an exchange transfusion or a blood transfusion to the infant, were known before pregnancy or were detected in screening test during current pregnancy. This study shows that the SPH-IAT test was sufficient for screening pregnant women. If the SPH-ENZ test had not been included in the screening test, no clinically significant alloantibodies would have been missed.