Predictive value of bone marrow megakaryocyte count for immunotherapeutic response in primary Sjögren's syndrome patients with severe immune thrombocytopenia: A single‐center case–control study in China

To investigate potential predictors of treatment response in primary Sjögren's syndrome (pSS) patients with severe immune thrombocytopenia (ITP), with a focus on bone marrow megakaryocyte (MK) count.This case-control study included patients with pSS and severe ITP who were admitted to Peking Union Medical College Hospital and met the 2002 AECG or 2016 American College of Rheumatology / European League Against Rheumatism criteria for SS. Patients who had overlap other connective tissue diseases and with thrombocytopenia that could be explained by other causes were excluded. Severe ITP was defined as platelet count <20 × 109 /L. Response was evaluated at 3 months after treatment.Sixty-eight eligible patients were included: 34 (50%) achieved complete remission (CR), 18 (26%) partial remission (PR) and 16 (24%) were non-responders (NRs). Fewer infections were found in the CR group (24%) than in the PR (50%) and NR (56%) groups (P = 0.04). The MK count (CR 32 vs PR 36 vs NR 4 per slide, P < 0.001) in the NR group was significantly lower than in the other groups. MK count >6.5 per slide predicted good treatment response, with 85.7% sensitivity, 88.1% specificity and 0.866 area under the curve. Logistic regression indicated that patients with more MKs were more likely to respond to immunotherapy (crude odds ratio [OR] 1.45, 95% CI 1.2-2.0, adjusted OR 1.68, 95% CI 1.2-2.7).MK count predicted response to immunosuppressive treatment in pSS patients with severe ITP. These patients are recommended to have bone marrow aspiration before treatment initiation. Clinicians should be aware of screening for infections during clinical practice.