10 STEP 10: Add known sensitized cells as a control for
11 STEP 11: Record results.
1 A positive result is agglutination in the anti-Rho(D) tube and
none in the control tube. This indicates Rho-variant activity, and the blood should be
classified as Rho-positive. A negative result is absence of agglutination in both tubes.
This means the cells do not have Rho(D) activity and should be classified as Rh
2 Cells which are agglutinated by antiglobulin serum in the
absence of added reagent antiserum have a positive antiglobulin test. If the control is
positive, the antiglobulin results of the anti-Rho(D) tube cannot be interpreted. If the
cells are from a patient needing a transfusion, he should be given Rh-negative blood. If
the cells are from a donor, the blood should not be used for transfusion.
3 Occasionally, when the albumin or the reagent control tube is
used for antiglobulin-testing, globulins in the medium may coat the cells during
incubation. To distinguish this from a truly positive direct antiglobulin test, repeat the
antiglobulin test on well-washed unincubated cells. If this is negative, the reagents used
for incubation should be investigated for the presence of immunologically active protein.
4 For false positives and false negatives refer to Subcourse
MD0846, Lesson 1, Section II.
c. Anti-Rho(D), Saline-Reactive.
(1) Saline-agglutinating Rh antibodies are useful for testing cells that
agglutinate spontaneously or form rouleaux when suspended in a high-protein medium.
Sometimes cells that are coated by anti-Rho(D) (as, for example, in hemolytic disease of
the newborn) or other antibodies (as, for example, in autoimmune hemolytic anemia)
can successfully be typed with saline-reactive antiserums, when antiserum for slide or
rapid tube test gives equivocal results. Saline-agglutinating Rh antibodies are
processed from pooled human serum and consist of human immunoglobulins.
(2) Since saline-reactive anti-Rho(D) agglutinates saline-suspended cells,
high-protein medium should not be used, and an albumin control is not indicated. If this
reagent is used only occasionally, the test should be accompanied by known positive
and negative controls. If the test is done frequently, the reagent should be tested as
part of the regular quality assurance program.