Positive rubella titers in pregnancy: a question of validity

A review of 25 patients with more than 1 rubella titer by hemagglutination-inhibition testing revealed 3 patients with high positive titers that were reported to be negative in subsequent pregnancies. None of the patients had received the rubella vaccine. Because the sensitivity and reliability of hemagglutination-inhibition testing is markedly influenced by multiple variables, it is important for both the clinician and the pathologist to be aware of both the limitations of the testing method and the meaning of an antibody titer on a single isolated specimen.