Researchers, led by Soo Min Ahn, examined patients with primary immune thrombocytopenia (ITP) who later developed systemic lupus erythematosus (SLE) and found that younger age, organ bleeding, and antinuclear antibody (ANA) positivity were potential risk factors for the occurrence of SLE. Their findings were published in Arthritis Research & Therapy.
This study included 130 patients from a tertiary hospital with a diagnosis of primary ITP between August 2001 and November 2019. Researchers used logistic regression to evaluate the prognostic relevance of clinical characteristics that differed between patients who developed SLE and those who did not.
Factors Predicting SLE After a Primary ITP Diagnosis
A total of 10 out of 130 (7.7%) patients with primary ITP were diagnosed with SLE over a median follow-up of 30 months (interquartile range, 15.5-105). The researchers determined that skin bleeding, organ bleeding, lymphocytopenia, anemia, and ANA positivity (defined as ≥ 1:160) were more common in the patients who later developed SLE compared with those who did not.
Multivariate analysis found that factors statistically significantly associated with the development of SLE were age less than 40 years (odds ratio [OR], 6.307; 95% CI, 1.114-34.908; P=.035), organ bleeding (OR, 13.672; 95% CI, 2.437-76.689; P=.003), and ANA positivity (OR, 6.638; 95% CI, 1.399-31.504; P=.017).
The study was limited by a potential selection bias due to its retrospective, single-center design. In addition, only patients who were diagnosed with SLE after a diagnosis of ITP were included, though the authors acknowledged that the data could not rule out ITP was one of the initial systematic symptoms of a case of primary SLE.
Nonetheless, the authors concluded that patients with primary ITP less than 40 years of age who had organ bleeding and/or ANA positivity were significantly associated with development of SLE within 1 year of their ITP diagnosis.