Risk of systemic lupus erythematosus in patients with idiopathic thrombocytopenic purpura: a population-based cohort study

Abstract

BackgroundIdiopathic thrombocytopenic purpura (ITP) may play a role in early-stage systemic lupus erythematosus (SLE). The incidence of SLE in patients with ITP and the potential relationship between them is still unclear. This study was performed to provide epidemiological evidence regarding the relationship between ITP and SLE occurrence.MethodsIn this population-based retrospective cohort study, the risk of SLE was analysed in a cohort of patients newly diagnosed with ITP between 2000 and 2013. Controls were selected at a 1:2 ratio through propensity score matching (PSM) using the greedy algorithm. The Cox proportional hazard model was used to analyse the association between ITP and SLE incidence. There were four different Cox regression models, and the sensitivity analyses were implemented to evaluate the HR of SLE after exposure with ITP.ResultsIn the age-matched and sex-matched ITP and non-ITP cohort, the average follow-up time was about 80 months in this study. There were 34 (4.70%) and 27 (0.19%) incident cases of SLE in ITP and non-ITP group. The incidence rates were 62.0 (95% CI 44.3 to 86.8) and 2.10 (95% CI 1.44 to 3.06), respectively. The adjusted HR of incidental SLE in the ITP group was 25.1 (95% CI 13.7 to 46.0). The other risk factors for SLE were female sex and Sjogren’s syndrome. After PSM, the incidence rate and Kaplan-Meir curves of SLE were consistent with the results for the age-matched and sex-matched population, the HR 17.4 (95% CI 5.28 to 57.4) was estimated by conditional Cox model.ConclusionThis cohort study demonstrated that patients with ITP have a higher risk of SLE. Clinically, patients with ITP should be monitored for incidental lupus.

Response to: ‘High risk of systemic lupus erythematosus development in patients with ITP: antiphospholipid syndrome is also a concern?’ by Inancet al

“…In our article, we concluded that ITP is strongly associated with incidental SLE. 2 We agree with Inanc et al 1 that antiphospholipid syndrome (APS) is an important effect modifier in ITP and SLE. We also acknowledge that Inanc et al 1 addressed the difference of APS (2.77% in the ITP group vs 0.02% in the non-ITP controls) in table 1 of our article.…”

“…We also acknowledge that Inanc et al 1 addressed the difference of APS (2.77% in the ITP group vs 0.02% in the non-ITP controls) in table 1 of our article. 2 Actually, ITP, APS and SLE sometimes overlapped in clinical practice. As in table 1, there are more baseline comorbidities in the ITP group, including thrombotic event, cardiovascular disease and ITP.…”

Correspondence on ‘Increased risk of systemic lupus erythematosus in patients with autoimmune haemolytic anaemia’

“…4 Zhu et al in their retrospective study based on the same population cohort even demonstrated that the patients with idiopathic thrombocytopenic purpura (ITP) had a 26-times higher risk of new-onset SLE compared with the control population. 5 Therefore, we suggest that the authors should investigate the difference in the incidence of SLE between patients with both AIHA and ITP and those with either AIHA or ITP. Besides, it has been proposed that both AIHA and autoimmune thrombocytopenia are associated with antiphospholipid antibodies, suggesting the presence of antibodies against the epitopes on the red cell membrane and platelets, probably the shared mechanisms in their pathophysiology.…”

Risk of systemic lupus erythematosus in patients with idiopathic thrombocytopenic purpura: population-based cohort study

“…According to the data presented in this study, the authors demonstrated that the patients with ITP had a 26 times higher risk of new-onset SLE in comparison with the control population. 1 Prevalence of ITP has been reported to be ranging between 7% and 30% in patients with SLE, while clinical characteristics of ITP in patients with SLE have been reported in several studies. 2 ITP is a haematological disorder characterised by thrombocytopenia, defined by low platelet counts, thus presenting with an increased bleeding risk due to an increased destruction of sensitised platelets by antibodies that react with glycoproteins expressed on platelets and megakaryocytes.…”

“…We read with great interest the article by Zhu et al 1 It was based on a national study regarding the association between idiopathic thrombocytopenic purpura (ITP) and the subsequent development of systemic lupus erythematosus (SLE), both representing clinically and genetically heterogeneous autoimmune diseases. According to the data presented in this study, the authors demonstrated that the patients with ITP had a 26 times higher risk of new-onset SLE in comparison with the control population.…”