Automated screening of antenatal samples using a low ionic strength polybrene system

The use of a two-channel AutoAnalyzer II system in the routine screening of antenatal sera is described. A low ionic strength polybrene method has been used to give optimum detection of IgG antibodies, and hence the system provides a valuable early detection of such antibodies in pregnancy. Of 88 Rhesus antibodies initially detected on the AutoAnalyzer only and followed up later in pregnancy, 18 (20.45%) were later detected by manual methods and were considered to be of potential clinical significance, whilst the remainder were detectable by the AutoAnalyzer only and occurred with a similar frequency as AutoAnalyzer only Rh antibodies in non-immunized males. The sensitivity of the method can provide interpretational difficulties, revealing many apparent "non-specific' reactions as well as detecting low levels of specific antibodies of debatable clinical significance. An approach to dealing with these problems without compromising the benefits of the system is discussed.