Clinical observation of hypofibrinogenemia induced by the treatment of tocilizumab in rheumatic diseases and exploration of risk factor for hypofibrinogenemia.

OBJECTIVE: The objective of this study was to analyze the changes in plasma fibrinogen (FIB) levels during tocilizumab (TCZ) treatment in patients with rheumatic diseases, to clarify the incidence of hypofibrinogenemia and its possible risk factors, and to establish a nomogram model for predicting the probability of hypofibrinogenemia in rheumatoid arthritis (RA) patients treated with TCZ.

METHODS: Clinical data of patients treated with TCZ at the Department of Rheumatology and Immunology, the First Affiliated Hospital of Xi'an Jiaotong University from January 2014 to October 2021 were retrospectively analyzed to observe the incidence of hypofibrinogenemia in several rheumatic diseases at different time points. The risk factor of hypofibrinogenemia in RA patients treated with TCZ was determined by using Cox regression analysis. Based on the results of Cox regression analysis, a nomogram for predicting the probability of hypofibrinogenemia in rheumatoid arthritis (RA) patients treated with TCZ was established and validated through RStudio software.

RESULTS: A total of 83 TCZ-treated patients were enrolled in this study, and 32 (38.55%) patients developed hypofibrinogenemia during TCZ treatment. There were 8 males and 24 females in the FIB-reduced group, with an average age of 44.88 ± 18.39 years. Hypofibrinogenemia was most common in TCZ-treated patients with takayasu arteritis (TA) and RA. Hypofibrinogenemia typically occured within 3 months after TCZ treatment. In RA patients treated with TCZ, platelet distribution width, parathyroid hormone, bone mineral density, tender joint count, and swollen joint count were independent risk factors for the occurrence of hypofibrinogenemia. The nomogram based on the above risk factors could effectively predict the probability of hypofibrinogenemia in RA patients receiving TCZ.

CONCLUSION: Although bleeding symptoms were not observed in this study, the incidence of hypofibrinogenemia remained high after TCZ treatment, usually occurring within 3 months of treatment. Therefore, it is necessary to monitor FIB levels during TCZ treatment. In addition, clinicians can use the nomogram model developed from this study to predict the incidence of hypofibrinogenemia after TCZ treatment in RA patients. Key Points • Hypofibrinogenemia often occurs during TCZ treatment for rheumatic diseases. • PDW, PTH, BMD, tender joint count, and swollen joint count are risk factors for the occurrence of hypofibrinogenemia. • It is necessary to monitor FIB levels during TCZ treatment to avoid bleeding tendency.