(3) There may be an unexpected antibody in some other blood group
system reacting with antigens on the A or B cells used for serum-testing. Anti-I is
probably the most common trouble-maker.
(4) The patient may have been given dextran, intravenously injected
contrast materials, or drugs that cause cellular aggregation that resembles
(5) The patient may have an immunodeficiency disease and lack expected
antibodies because of low overall immunoglobulin levels.
(6) The patient may be an infant who has not begun producing his own
antibodies, or who has antibodies passively received from the mother.
(7) The patient may be an elderly person whose antibody levels have
(8) The patient may have antibodies against elements of the preservatives,
suspending mediums, or reagent solutions used in testing.
f. Resolving Discrepancies. Many problems can be resolved by repeating the
tests and washing the cells thoroughly before testing them. Obtaining a new sample of
blood from the patient corrects difficulties introduced by contaminated specimens. The
most frequent causes for persisting problems are the presence of rouleaux-producing
factors in serum; the presence of unexpected antibodies; the presence of anti-I, which
reacts with nearly all cells, including the patient's own cells; and the presence of
antibodies coating the cells (positive antiglobulin test). In handling a persistent problem,
be sure to:
(1) Look at results of an antibody-screening test. If test is positive, identify
the antibody. For serum-testing, use A and B cells that lack the antigen involved, if
these can be obtained.
(2) Determine subject's age, diagnosis, previous medications, or
transfusions, and serum protein findings.
Perform antiglobulin test on patient's cells.
(4) Perform an autologous control test, using patient's serum and
suspension of the patient's cells. Both rouleaux factors and auto-anti-I will cause
autoagglutination. It is usually possible to autoabsorb anti-I. Rouleaux formation can
often be diminished by adding additional saline to the cell-serum mixture.