In the first stage, red cells are treated with the enzyme (by incubating with the enzyme solution for about 10 - 15 minutes). These cells are washed, to remove the enzyme, then incubated with serum as described above for the one-stage test. This incubation is the second stage of the test. The two-stage test is more sensitive than the one-stage test and can't break the antibody apart, since enzyme and serum are never incubated together.
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| Two-Stage Test |