The distribution of antinuclear antibody titers in "normal" children and adults.

Abstract

To characterize the antinuclear antibody (ANA) titer distributions and patterns in normal subjects, segregated by age and sex. Sera were obtained from 183 blood donors (130 females, 53 males) aged 20-63 years, from 200 schoolchildren (100 females, 100 males) aged 10-19 years, and from 237 children (102 females, 135 males) aged 3 months to 9 years whose sera were received for unrelated clinical testing. ANA was assayed by indirect immunofluorescence using HEp-2 cells as substrate. In adults, ANA titers were slightly higher in females than in males (p=0.053); there was no sex effect in subjects aged <20 years. ANA titer increased significantly with age only among females (p<0.01). Homogeneous staining was associated with lower titers than speckled or nucleolar staining (p=0.058), at least in part because of antigen density in the test substrate itself. The frequency of cytoskeletal staining decreased (p<0.01) with age, while that of nucleolar staining increased (p<0.01). Reference ranges for ANA vary by age, sex, and immunofluorescence pattern. Therefore, all these variables must be considered in the interpretation of ANA results.