Fluctuation of virus antibody levels in healthy adults

In order to determine fluctuations in virus antibody levels, blood specimens were collected weekly from 13 healthy adults during a nine-week period and tested by enzyme immunoassay for IgG antibodies against measles, rubella and cytomegalovirus. In 29 of 35 subject-titer pairs the difference between the highest and lowest titers observed was less than twofold, in five cases it was between twofold and threefold, and in one case it was 3.3-fold. These differences were higher than those caused by intraassay variation alone. The results indicate that some physiological fluctuations seem to occur in the antibody levels of healthy individuals. Although the fluctuations are usually small, care should be taken if titer increases less than fourfold are used as a criterion to indicate recent infection.