ANA-positive ITP linked to higher autoimmune disease risk
Patients may show symptoms that resemble lupus, Sjögren’s disease
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Patients with immune thrombocytopenia (ITP) who test positive for antinuclear antibodies (ANA), which mistakenly target the nucleus of cells, are at higher risk of developing other autoimmune diseases, such as lupus and Sjögren’s disease, researchers in China have found.
The study, “Antinuclear antibody positive in patients with primary immune thrombocytopenia: incidence and risk prediction of developing autoimmune diseases,” was published in Hematology.
In ITP, the immune system mistakenly attacks and destroys platelets — the cell fragments responsible for blood clotting — leading to symptoms such as easy bruising and prolonged bleeding. The disease is considered primary when there is no identifiable underlying cause for it, such as an infection, cancer, or another autoimmune disease.
Patients with primary ITP who test positive for ANA may show symptoms that resemble the early stages of autoimmune diseases, such as lupus or Sjögren’s disease, though they are still considered to have primary ITP because the risk of progression to other autoimmune diseases is not fully understood.
“ANA has emerged as a biomarker for patients with primary ITP without definitive autoimmune diagnoses,” the researchers wrote. “These findings suggest that ANA-positive primary ITP is a distinct clinical entity.”
Assessing risk in ANA-positive ITP patients
Researchers sought to assess the risk of autoimmune disease development and progression among patients with primary ITP who tested positive for ANA.
Of 360 patients diagnosed with ITP, 261 (72.5%) tested positive for ANA. Autoimmune diseases were more frequent among ANA-positive versus ANA-negative patients (81.2% vs. 52.5%), including systemic lupus erythematosus, the most common form of lupus (22.6% vs. 8.1%), and Sjögren’s disease (37.6% vs. 19.2%).
The risk of developing any autoimmune disease was 16.8 times higher in ANA-positive patients. On average, autoimmune diseases developed 16.1 months after an ITP diagnosis. However, not all ANA-positive patients with primary ITP developed an autoimmune disease.
Subgroup analyses comparing ANA-positive patients who went on to develop autoimmune diseases with those who did not showed some differences in the levels of C3 and C4, two proteins that are part of the immune system’s complement cascade, and in certain self-reactive antibodies, such as anti-LA, anti-Ro60, anti-Ro52, and anti-SSA.
Based on these findings, the researchers created risk scores to predict the likelihood of developing autoimmune diseases or Sjögren’s disease. The risk score for autoimmune disease development combined ANA positivity, anti-SSB positivity, and C3 levels, while the Sjögren’s risk score included ANA positivity, anti-Ro52 positivity, and C3 levels.
Using these scores, the team developed graphical tools (called nomograms) that estimate a patient’s probability of remaining free of autoimmune diseases or Sjögren’s disease at 1.5 and 2 years after an ITP diagnosis. These tools may help clinicians identify high-risk patients early and monitor them more closely.
