Definition: In reverse typing a sample of blood is mixed with type A and type B blood, and clotting patterns are observed and recorded.

Explanation: ABO typing: The ABO typing process consists of forward and reverse typing.

In forward typing a sample of the blood is mixed with serum that contains antibodies against type A blood ("anti-A serum"). Another sample of blood is then mixed with serum that contains antibodies against type B blood ("anti-B serum"). Patterns of clotting are observed and recorded.

In reverse typing a sample of blood is mixed with type A and type B blood, and clotting patterns are observed and recorded.

Reverse typing means that:

* Serum from type A blood clots when mixed with type B blood.
* Serum from type B cells clots when mixed with type A blood.
* Serum from type O blood clots when mixed with type A and type B blood.
* Serum from type AB blood does not clot when mixed with type A or type B blood.

Source: http://atoz.iqhealth.com/HealthAnswers/encyclopedia/HTMLfiles/1084.html