Paul J. Maglione, United States of America
Boston University School of Medicine Pulmonary, Allergy, Sleep and Critical Care MedicinePresenter of 1 Presentation
SERUM B CELL MATURATION ANTIGEN (BCMA) LEVELS DIFFERENTIATE PRIMARY ANTIBODY DEFICIENCIES
Abstract
Background and Aims
Primary antibody deficiencies (PAD) are the most prevalent primary immunodeficiencies. Severer forms of PAD, common variable immunodeficiency (CVID) and X-linked agammaglobulinemia (XLA), require immunoglobulin replacement therapy (IRT) and may lead to serious complications. Differentiating severe PAD from hypogammaglobulinemia not requiring IRT can involve prolonged evaluations and treatment discontinuation. Severe PAD is defined by plasma cell deficiency, but this requires biopsy to establish. Serum B cell maturation antigen (sBCMA) is elevated in multiple myeloma, but levels are reduced among myeloma patients in complete remission who have hypogammaglobulinemia. We measured sBCMA levels in 165 subjects to determine whether it differentiates the severe PAD, CVID and XLA, from less severe forms not requiring IRT and those without PAD.
Methods
sBCMA, B-cells, and tissue plasma cells were measured among subjects with and without PAD, and correlated to clinical and laboratory data.
Results
Subjects with IgG < 600 mg/dL had reduced sBCMA levels compared with PAD with IgG ≥ 600 and non-PAD controls. sBCMA was lower in CVID and XLA compared to IgA or IgG deficiency and non-PAD controls. sBCMA correlated with gastrointestinal plasma cells. sBCMA < 15 ng/mL had 97% positive predictive value for CVID or XLA, while 25 ng/mL or more had 88% negative predictive value.
Conclusions
sBCMA is profoundly reduced in severe PAD, including CVID, XLA and subjects with IgG < 600 mg/dL. sBCMA measurement has potential to augment clinical evaluation of PAD. Prospective studies are needed to evaluate sBCMA for new PAD diagnosis and determining necessity of IRT.