Ratio of involved/uninvolved immunoglobulin quantification by Hevylite？ assay: clinical and prognostic impact in multiple myeloma

HevyLite？ assays were used in sera from 130 healthy individuals (HI) and 103 MM patients, at time of diagnosis. In patients, the level of paraprotein was IgG in 78 (52 IgG-kappa, 26 IgG-lambda) and IgΑ in 25 (13 IgΑ-kappa, 12 IgΑ-lambda). Durie-Salmon and International Staging System stages were evenly distributed. Symptomatic patients (n = 77) received treatment while asymptomatic ones (n = 26) were followed. Patients' median follow-up was at 32.6 months. HLCR was calculated with the involved Ig (either G or A) as numerator.In HI, median IgG-kappa was 6.85, IgG-lambda 3.81, IgA-kappa 1.19 and IgA-lambda 0.98 g/L. The corresponding median involving HLC values in MM patients were 25.8, 23.45, 28.9 and 36.4 g/L. HLC-IgG related to anemia, high serum free light chain ratio and extensive bone marrow infiltration, while high HLCR correlated with the same plus increased β2-microglobulin. In addition, increased HLCR and the presence of immunoparesis correlated with time to treatment. Patients with high HLCR had a significantly shorter survival (p = 0.022); HLCR retained its prognostic value in multivariate analysis.HLC and HLCR quantify the precise amount of the involved immunoglobulin more accurately than other methods; moreover, they carry prognostic information regarding survival in MM patients.Multiple myeloma (MM) is characterized by bone marrow (BM) plasma cell infiltration and the presence of serum/urine monoclonal immunoglobulin (Ig). Disease manifestations and behavior vary widely, while survival ranges from a few months to more than a decade.Serum monoclonal Ig quantification is part of MM diagnostic criteria, and one of Durie and Salmon (DS) staging system's risk factors [1]. It is also used for monitoring response and relapse. However, MM aggressiveness is not related to the amount of Ig secretion, and newer staging systems did not retain Ig quantity as a risk parameter [2].The poor utility of IgG and IgA measurements may be related to the following:1) Changes