Introduction to Rh (D) Typing

Rh(D) typing is an important part of pretransfusion testing. Because the D antigen is very immunogenic, there is an ~70% chance that an Rh(D)-negative recipient will form anti-D following transfusion with D-positive red cells. Thus, Rh-negative patients routinely receive only Rh(D)-negative donor units. This protocol is particularly critical for females in the child-bearing years or younger, in whom anti-D could cause hemolytic disease of the newborn.

Historically, four anti-D typing reagents have been used. As discussed below, each antiserum has its own characteristics, strengths and weaknesses.

Determination of Rh (D) Type

Slide and Modified Tube Anti-D
Saline Anti-D
Chemically Modified Anti-D
Monoclonal/Polyclonal Blend Anti-D

Enrichment Activity 3

(available only to those enrolled in the DE course)

Read RhIg as a source of passive anti-D, a Medline abstract of a study done to identify antibodies in women injected with RhIg by using a work-saving protocol.

Answer the following questions based on the abstract and e-mail replies to Pat.

  1. Why did the authors expect an increase in detecting anti-D in Rh-negative women about 1987?

  2. Describe the time-saving testing protocol that the authors developed to determine if positive antibody screen tests in Rh-negative patients were due to anti-D alone.

  3. Of 1174 Rh-negative patients with positive antibody screen, how many had anti-D alone? How many had anti-D plus a non-D antibody? How many had a non-D antibody (but no anti-D)?

  4. What do the authors cite as evidence that the abbreviated test protocol is safe?

Determination of Rh (D) Type

©1999 Division of Medical Laboratory Science
University of Alberta