The following are crossmatch practices seen in the USA and Canada for the scenario outlined earlier for women with passive anti-D likely due to RhIg. Laboratories may perform:
- Full serologic crossmatch* with Rh negative RBC as long as the anti-D can be detected. Once it becomes undetectable, either an IS or electronic crossmatch is performed, according to routine policies for patients who lack clinically significant antibodies and meet other criteria for an electronic crossmatch;
- IS crossmatch;**
- Electronic crossmatch.**
As shown, crossmatch policies are diverse:*Some labs treat RhIg-derived passive anti-D the same as clinically significant immune antibodies, except for when it becomes undetectable;**Some labs treat RhIg-derived passive anti-D differently than immune antibodies, and use crossmatch protocols identical to those for clinically insignificant antibodies.