Clinical significance of the antinuclear antibody test in selected children with idiopathic thrombocytopenic purpura

Purpose: To determine the clinical significance of the antinuclear antibody (ANA) test in selected children with idiopathic thrombocytopenic purpura (ITP). Methods: The study was conducted through retrospective chart review and long-term follow-up by telephone interview. Results: Of 87 children with ITP who had an ANA performed, 25 had a positive titer (median=1:160, range: 1:40 to 1:2,560). Children with a positive ANA were more likely to be older girls who developed chronic ITP, but there was no correlation with family history of autoimmune disease, initial hemoglobin concentration, or initial platelet count. With an average follow-up of more than 5 years, more children with a positive ANA developed further autoimmune symptoms than those with a negative ANA (36% vs. 0%, p < 0.001). Nine children with a positive ANA developed additional autoimmune symptoms, including five with clinical criteria sufficient for the diagnosis of systemic lupus erythematosus (SLE). Autoantibodies to dsDNA were more prevalent in the children with progression of autoimmune symptoms (57% vs. 0%, p = 0.04). The presence of any autoantibody in addition to the ANA, including dsDNA, SS-A/Ro, SS-B/La, Smith Antigen (Sm), nuclear ribonucleoprotein (nRNP), or cardiolipin was more common in children who had further autoimmune symptoms (75% vs. 0%, p = 0.003). Conclusions: The ANA is a useful screening test in a subset of children with ITP, especially older girls with chronic ITP, who are at risk for the development of generalized autoimmune disease. Children with ITP and a positive ANA should receive careful follow-up.