Antinuclear antibody (ANA) and ANA profile tests in children with autoimmune disorders: A retrospective study

The study objective was to determine the clinical value of positive antinuc lear antibody (ANA) and ANA profile tests in children with autoimmune disor ders. A retrospective chart review was carried out of all patients under 18 years of age with a positive ANA test (HEp-2 cell substrate, titre greater than or equal to 1:40) and ANA profile (ELISA) referred to the paediatric rheumatology service at the authors' institution between 1992 and 1996. Of 245 children with a positive ANA test, 134 (55%) had an autoimmune disease, including juvenile rheumatoid arthritis (n=49), systemic lupus erythematos us (SLE) (n=40) and others (n=45). The remaining 111 patients did not have identifiable autoimmune diseases. Patients with autoimmune disorders had si gnificantly higher ANA titres of greater than or equal to 1:160 (chi(2) = 1 6, P < 0.0001). Ln addition, of the 245 patients with a positive ANA test, 86 had an ANA profile performed; this was positive in 32 and negative in 54 . All 32 patients with a positive ANA profile (100%) had an autoimmune diso rder, compared to 22 (41%) of 54 with a negative ANA profile who had autoim mune disorders. Of 22 SLE patients with a positive ANA profile, 16 (73%) ha d positive anti-dsDNA and 15 (68%) had positive anti-Sm and positive anti-R NP. A positive ANA profile correlated strongly with an ANA titre greater th an or equal to 1:640 (chi(2) = 5.7, P < 0.02). The study demonstrated that only 55% of children with a positive ANA test had a definitive diagnosis of autoimmune disorder. These children tend to have higher ANA titres of grea ter than or equal to 1:160. However, a positive ANA profile was strongly co rrelated with an ANA titre greater than or equal to 1:640 and highly indica tive of an autoimmune disorder (100%). We suggest that in order to reduce c ost, an ANA profile should not be performed on all patients with positive A NA, but reserved for those with an ANA titre of greater than or equal to 1: 640 and/or these with a high clinical index of suspicion for autoimmune dis order, especially SLE.