PB0661 - Platelet response following dexamethasone in obese vs. non-obese patients with primary, acute immune-mediated thrombocytopenia

Background: Glucocorticoids remain preferred front-line therapy for acute ITP. Fixed-dose oral dexamethasone 40 mg daily for four days is frequently used. For refractory disease, however, guideline recommendations for subsequent courses are lacking. To date, ten publications have described effective use of repeat courses, with overall response rates ranging between 63-100%, however data are limited for predicting response. Obesity is common among patients with ITP, yet the effect of obesity on dexamethasone response remains unknown.

Aims: Herein, we investigated whether response rates to dexamethasone differed between non-obese and obese patients with primary, acute ITP.

Methods: A single-center, retrospective, IRB-approved chart review at the University of Utah was performed. Eligible patients were 18 years or older. Patients were categorized as obese (BMI ≥30mg/m2) or non-obese (BMI < 30mg/m2). Outcomes were assessed over 6 months. The primary outcome, overall response rate, was defined as an increase in platelet count to ≥30,000/μL with ≥2-fold increase from baseline. Additional outcomes included type and time to response, number of dexamethasone courses received, and requirement for alternative therapy. Chi-square test and Wilcoxon rank sum were used, with an a priori alpha of 0.05.

Results: 117 patients were eligible. Of these, 49 had primary, acute ITP. Baseline characteristics were comparable. For the primary outcome, a significantly higher response to dexamethasone was observed in non-obese patients (93%) compared to obese (71%) (p=0.04). Additionally, only 48% of obese patients vs. 68% of non-obese achieved a complete response. When combining patient groups, 71% of initial non-responders did not receive subsequent dexamethasone courses prior to implementing alternative therapy.

Conclusion(s): Our results show that obese patients with primary, acute ITP have lower initial, and complete response rates than patients without obesity. Moreover, repeat dexamethasone courses are underutilized in all patients with ITP, especially those with obesity. Future prospective studies designed to improve response rates to dexamethasone are needed.