False-positive results with chemically modified anti-D.

Chemically modified anti-D typing serum is considered to combine the reliability of saline IgM anti-D with the convenience of slide and rapid tube anti-D. This has led to its wide acceptance in modern blood bank practice. False-positives are considered rare and are controlled by the ABO grouping. The extra step of an Rh control, which is necessary with IgG slide and rapid tube anti-D serums, is thus eliminated. However, this report shows that adopting this practice can be misleading and dangerous. Two cases are reviewed in which the chemically modified anti-D gave false-positive results and the ABO typing did not act as an adequate control.