3 STEP 3: Add one or two drops of 2 to 5 percent cell suspension in
serum or saline to each tube OR use clean, separate applicator stick to dislodge sufficient
cells from clot to approximate cell volume in one drop of 5 percent suspension in each
5 STEP 5: Gently resuspend cell button and observe for
agglutination. If stick was used to transfer cells, adding one drop of saline to the tube
before resuspending cell button will provide more fluid and make resuspension and
6 STEP 6: Record test and control results.
(b) Interpretation. A positive result is agglutination in the anti-Rho(D)
tube and a smooth suspension in the control. If the anti-Rho(D) tube is not agglutinated,
the test can be continued immediately for Du. If there is agglutination or irregularity in
the control tube, a saline test must be performed (see below).
1 If cells and serum remain together too long before test is read,
the high-protein medium may produce rouleaux which resemble agglutinates.
2 If a combined antibody (for example, anti-Rhorh'(DC)) is used instead of
anti-Rho(D), cells which lack Rho(D) but contain the other antigen may be agglutinated.
3 Some specificity other than anti-Rho(D) may be present in the
1 If cells and serum remain together too long before tests are
read, antibody may elute from weakly reactive cells, and small agglutinates may
2 Failure to identify reagents at time of use may result in albumin,
antiglobulin serum, or some other colorless reagent being added instead of anti-Rho(D).
3 Inadvertent failure to add reagent (as, for example, in one of the
long row of tubes) will give smooth suspension of cells.