Assays for detecting and diagnosing antibody-mediated pure red cell aplasia (PRCA): an assessment of available procedures

Antibody (Ab)-mediated pure red cell aplasia (PRCA) develops when patients mount a neutralizing Ab response to recombinant erythropoiesis-stimulating agents (ESAs) such as epoetin-alpha (EPO). These neutralizing Abs can also cross-neutralize endogenous EPO, leading to a state of absolute EPO resistance and transfusion dependence. The diagnosis of Ab-mediated PRCA in part relies oil the sensitive and specific detection of serum anti-EPO Abs and a confirmatory examination of patients' bone marrow for lack of erythroid precursors. To date, a variety of assays have been used to detect anti-EPO Abs, including radioimmunoprecipitation (RIP) assay, enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR) and bioassays that measure neutralizing Abs. Each of these assays can yield informative results and possess characteristic benefits and limitations, so it is unclear whether or not a 'superior' assay is required or possible. To date, a universal standardized assay has not yet been established that would facilitate the comparison of Ab data derived from different laboratories and retrospective analysis of stored sera. This review evaluates the results of studies measuring anti-EPO Abs with different assays and compares their relative advantages and disadvantages in terms of specificity, sensitivity, ease of use and ability to measure Ab-binding affinities and subclasses. These comparisons provide a basis for determining the optimal assay(s) for screening and/or analysis of patients' serum for anti-EPO Abs during treatment or after onset of Ab-mediated PRCA.