Primary immune thrombocytopaenia (ITP) is highly heterogeneous. ANA-positive primary ITP may resemble the preclinical stage of connective tissue diseases (CTDs), but is still considered primary ITP due to a controversial CTD risk assessment in this group. The objective of this study was to clarify the risk of CTD in ANA-positive patients with primary ITP.
We performed a retrospective cohort study and a meta-analysis. 586 patients with newly diagnosed primary ITP were followed up and Cox regression analyses were used to analyse the associations of ANA positivity and other immune parameters with CTD development.
The mean follow-up time was 37 (19-56) months. ANA was positive in 21.33% (125 of 586) of patients with primary ITP in our retrospective cohort, and the overall rate of ANA positivity in the meta-analysis was 17.06% (369 of 2163). The adjusted HR for CTD in ANA-positive primary ITP was 6.15 (95% CI 2.66 to 14.23, p<0.001). Five patients in the ANA-positive group developed SLE (5 of 125, 4.0%), significantly higher than in the ANA-negative group (0 of 461, 0%). A clinical model combining ANA, anti-Sjogren's syndrome A antibody and C3 was successfully developed to predict the risk of CTD in patients with primary ITP. Increased risk of CTD (risk ratio=12.43, 95% CI 7.91 to 19.55, p<0.00001), especially SLE (risk ratio=30.41, 95% CI 13.23 to 69.86, p<0.00001), among ANA-positive patients with primary ITP was confirmed by a meta-analysis of previous studies and the present study.
The findings suggest that ANA-positive primary ITP is a clinical entity distinct from other primary ITPs and is associated with increased risk of developing CTDs, especially SLE.