Objective: To characterize the antinuclear antibody (ANA) titer distributions and patterns in normal subjects, segregated by age and sex.
Methods: 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.
Results: 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).
Conclusion: Reference ranges for ANA vary by age, sex, and immunofluorescence pattern. Therefore, all these variables must be considered in the interpretation of ANA results.