(2)
Resolving errors in technique.
(a) Check identification of all samples and materials. If a blood sample
is found to be incorrectly labeled, immediately begin efforts to find out why. Often two
samples will have been switched, so look for another sample drawn, received, or
processed at the same time and place.
(b) Repeat tests, using clean glassware and different reagents, with
careful attention to timing of centrifugation or tilting slide and to use of positive and
negative controls.
(c)
Thoroughly wash patient's cells before making cell suspension.
d. Problems with Red Blood Cells.
(1) The cells may appear to be agglutinated because something in the
patient's serum (Wharton's jelly or serum proteins causing rouleaux) remains in the cell
suspension tested.
(2) The patient may have antibody-coated cells, which agglutinate in a
high-protein medium.
(3) The patient may have received transfused cells and the sample is a
mixture of cell types.
(4)
The A or B antigens may be weakly expressed because of an unusual
genotype.
(5) The A or B antigens may be weakened by the effects of leukemia or
non-hematologic malignant conditions.
(6) The cells may have genetic or acquired surface abnormalities that
render them polyagglutinable.
(7) There may be acquired "B-like" activity, usually resulting from action of
gram-negative organisms.
e. Problems with Serum.
(1) High concentrations of fibrinogen or of abnormal proteins, or altered
proportions of globulins, may cause rouleaux formation, which resembles agglutination.
(2) There may be an unexpected antibody reacting with A, B, or H antigens.
The most common are anti-A1 in A2 or A2B serums, and anti-H in A1 or A1B serums.
MD0845
2-20
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