treatment, so the success or failure of immunosuppression cannot be evaluated until at
least 6 months after the transfusion. Rh immune globulin should be given as soon as
possible after Rh-positive cells have been transfused, but successful
immunosuppression has been reported with delay as long as 72 hours before beginning
injections. When large amounts of globulin must be given intramuscularly, divided
doses over a period of several days can be therapeutically effective.
2-26. Rh-TYPING
a. General. Routine cell-typing for patients and donors alike involves only
Rho(D) with techniques to demonstrate Du being required for donor bloods. Tests for
other Rh antigens are performed when there are specific reasons for detailed testing,
such as parentage determination or other family studies, or attempts to distinguish
between homozygous or heterozygous Rh-positives. Potential donor bloods should
always be tested for the relevant antigen if the recipient has an antibody. In selecting
blood for the recipient with an antibody, testing with reagent antiserums gives more
reliable results than relaying merely on a negative cross-match. Except for clearly
defined indications, routine testing for Rh antigens other than Rho(D) is not
recommended.
b. Anti-Rho(D) Serum for Slide or Rapid Tube Test. This reagent gives rapid,
reproducible results when used according to manufacturer's directions, provided the
cells are not antibody-coated or otherwise abnormal. Since false positive agglutination
readily occurs, a control with immunologically inert reagents must accompany each test.
If cells are agglutinated in the control procedure, the results of the anti-Rho(D) test are
invalid, and the cells must be tested with a reagent unaffected by protein abnormalities.
(See section below on saline-agglutinating reagents.)
(1) The control. False positives are caused by interaction between the red
blood cells under test and the non-antibody materials in the reaction mixture. Not only
the macromolecular nature of the medium, but specific substances in the reagents may
cause cellular aggregation that resembles antibody-mediated agglutination. The best
control medium to detect these events is the material used in the antiserum, which lacks
only the specific antibody. Many manufacturers offer immunologically inert high-protein
mediums that resemble the reagent in all other ways. The Rho(D) test should be
controlled with this material, if it is available. In the absence of inert serum diluent, 22
pecent or 30 percent bovine albumin can be used. The serum diluent used for Rh-testing
should not be used as the high-protein additive for cross-matching or antibody-screening or
identification procedures.
(2)
Slide testing.
(a) This requires a high concentration of cells and protein and an
optimum temperature of 37C. The viewing surface should be kept lighted at all times
to preserve a temperature of 45C to 50C. Reagents placed on a glass slide in contact
with the surface should reach 37C within 2 minutes.
MD0845
2-38