Adjunctive treatment of clinically severe babesiosis with red blood cell exchange: a case series of nineteen patients

BACKGROUND Infection with the protozoan parasite Babesia, the causative agent of babesiosis, can result in asymptomatic to life‐threatening illness. Severe cases of babesiosis are characterized by high levels of parasitemia (>4%‐10%) and commonly treated with adjunctive red blood cell exchange (RCE) in addition to antimicrobial therapy. The efficacy of RCE in this context is unknown. STUDY DESIGN AND METHODS Blood bank records were examined for requests for RCE during a 10‐year period from 2007 to 2017. Relevant clinical and laboratory variables were extracted from medical records from presentation to 35 days after RCE and analyzed in univariate and multivariate models. RESULTS Nineteen cases of babesiosis were identified in which RCE was performed. The median age of patients was 77 years, 74% of whom were male. A total of 37% of patients were asplenic. RCE was performed on average 1.3 days after presentation, with procedural urgency driven mainly by the level of parasitemia. Mean pre‐ and post‐RCE levels of parasitemia were 12.9 and 3.4%, respectively, resulting in a mean percent reduction in parasitemia of 75%. Preprocedural parasitemia (p = 0.047) and age (p = 0.028) were both significant predictors of postprocedural hospital length of stay (post‐RCE LOS). Neither postprocedural parasitemia (p = 0.12) nor percent reduction in parasitemia (p = 0.72) correlated with post‐RCE LOS. Four patients died, none of whom were asplenic. Mortality was not correlated with hematologic, parasitologic, or clinical variables analyzed. CONCLUSIONS Reduction in the level of parasitemia is the only known benefit of RCE in severe babesiosis.