VPB1222 - High Frequency of Bone Marrow Evaluations but Low Diagnostic Yield in Relapsed or Refractory Immune Thrombocytopenia

Background: The diagnosis of primary immune thrombocytopenia (ITP) is one of exclusion. While consensus guidelines recommend against routine bone marrow examination (BME) in typical ITP, the role of BME in relapsed/refractory ITP has not been studied.

Aims: 1. To examine the prevalence and predictors of BME in relapsed/refractory ITP. 2. To assess the prognostic impact of abnormal bone marrow on management.

Methods: This multi-centre retrospective cohort study included all chronic ITP patients ≥18 years who received second-line therapy (rituximab, thrombopoietin receptor agonists [TPO-RA], splenectomy) between 2012-2019 in Alberta, Canada. We calculated the frequency of BME and the rate of abnormal marrow findings. Logistic regression analyses were conducted to assess BME predictors such as age, sex, rural residence, ITP etiology, laboratory parameters, and response to second-line therapies. Research ethics approval was obtained.

Results: We identified 324 patients who received second-line therapy. 181 (56%) patients underwent a BME, at a median age of 61. We observed a marked decline in the rates of BME among patients >60 years over the past decade, from 86% (2008-2010) to 30% (2017-2019), but not in patients under 60 years (Figure 1). On univariate logistic regression, older age (OR 1.02, P< 0.001), male sex (OR 1.7, P=0.02), splenectomy (OR 2.1, P=0.002) or TPO-RA (OR 1.9, P=0.006) were significant predictors of undergoing BME (Table 1), while response to splenectomy (OR 0.25, P=0.005) and rituximab (OR 0.5, P=0.03) were associated with lower odds of BME. Of the 181 patients who underwent BME, only 8 (4%) had abnormal marrow findings and of those, 4 experienced changes in clinical management.

Conclusion(s): While BME is frequently performed in relapsed/refractory ITP, abnormal findings are uncommon in most patients. Analysis examining predictors of abnormal marrow findings is ongoing and may help identify a subgroup of relapsed/refractory ITP who may benefit from BME.