CLINICAL LAB SCIENEC

428
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
MANUAL IMMUNOHEMATOLOGY PROCEDURE #5
Blood Typing for the Rh Factor, Slide and Tube Method
Principles
The Rh blood system is composed of many antigens, but the first to be discovered
was that of the D antigen. Normally when screening patients and units of blood for
the Rh factor, the only antigen that is initially tested for is the D antigen. Others may
be tested for in certain medical conditions, and are pursued following the determination
of the presence of the D antigens. RH antigens may occur in a number of
combinations, but the “big D” antigen is the one most commonly associated with
incompatibilities when preparing units of blood for transfusion, and in certain diseases
of the unborn child when the mother is Rh negative. An Rh negative mother
may develop antibodies against her baby while it is in the uterus, requiring treatment
before and after birth to save the fetus’s life.
A “weak” D antigen, often denoted as D u , is tested for by incubating washed
RBCs with anti-D sera and then treating the specimens with a commercial immunoglobulin
G (IgG) to detect antibodies bound to the red cells in the initial test procedure
for a “normal” D antigen. Several dozen more antigens other than D have been identified
in the Rh typing system, but many of them are extremely rare. The most common
of these include C (big C), c (little c), E (big E), and e (little e). Individuals who do not
have this antigen on their RBCs and who are transfused with blood containing these
antigens may develop antibodies against them, which may cause problems in women
who have children whose blood contains these antigens.
This procedure provides an initial review of some of the kinds of testing laboratory
technical personnel perform. It will cover only the determination of the presence
or absence of the D antigen (“big D”). As in the ABO grouping procedure, there are
two methods for Rh determination: a tube method and a slide method. Washing of
the red cells is not normally done for the slide method, but a newborn’s cord blood
contains a material that interferes with the normal testing procedure, so washing
of the RBCs in this case is necessary. Unlike the ABO grouping, which will occur at
room temperature, the test for the Rh factor, when performed as a slide test, requires
warming of the slides during the test.
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant or other cleaning solution
2. Report form
3. EDTA anti-coagulated blood specimen (for the slide method), and a 2% to 5% RBC
suspension of washed RBCs from the patient being tested, prepared following the
steps set out in Procedure #1 (for the test tube method)
4. Wax pencil or other permanent marker
5. Normal physiological (0.85%) saline (blood bank quality) in squeeze bottle
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.