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

Objective. To characterize the antinuclear antibody (ANA) titer distributio ns and patterns in normal subjects, segregated by age and sex. Methods, Sera were obtained from 183 blood donors (130 females, 53 males) a ged 20-63 years, from 200 schoolchildren (100 females, 100 males) aged 10-1 9 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 assa yed by indirect immunofluorescence using HEp-2 cells as substrate. Results, In adults, ANA titers were slightly higher in females than in male s (p = 0.053); there was no sex effect in subjects aged <20 years. ANA tite r increased significantly with age only among females (p < 0.01), Homogeneo us staining was associated with lower titers than speckled or nucleolar sta ining (p = 0.058), at least in part because of antigen density in the test substrate itself. The frequency of cytoskeletal staining decreased (p < 0.0 1) with age, while that of nucleolar staining increased (p < 0.01), Conclusion. Reference ranges for ANA vary by age, sex, and immunofluoresenc e pattern. Therefore, all these variables must be considered in the interpr etation of ANA results.