We thank Dr Mertz and Arnaud1 for their comments on our recent article in the Annals of the Rheumatic Diseases entitled ‘Risk of systemic lupus erythematosus in patients with idiopathic… Click to show full abstract
We thank Dr Mertz and Arnaud1 for their comments on our recent article in the Annals of the Rheumatic Diseases entitled ‘Risk of systemic lupus erythematosus in patients with idiopathic thrombocytopenic purpura: a population-based cohort study’.2 They raised the question about selection of control group and suggest a control group consisting of patients with other autoimmune diseases, such as autoimmune haemolytic anaemia (AIHA), Evans syndrome and thyroiditis, instead of using a standard control group. We agree that many immune-mediated diseases or chronic infectious diseases might also be attributed to systemic …
               
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