A NOVEL multivariable model can predict smouldering multiple myeloma (SMM) in patients with monoclonal gammopathy of undetermined significance (MGUS), according to recent research. The model aims to enhance decision-making regarding the necessity of bone marrow sampling in patients suspected of having SMM, a precursor condition to multiple myeloma.
“A diagnosis of MGUS represents a dilemma,” explained lead author Elias Eythorsson, University of Iceland, Reykjavík, Iceland. “It is an asymptomatic precursor to multiple myeloma and related diseases, but the majority of individuals with MGUS will never progress to these diseases. In this sense, MGUS is not itself a disease but rather a risk factor for disease.”
The study, which involved 1,043 Icelandic adults aged ≥40 years, focused on individuals diagnosed with different forms of MGUS (IgG, IgA, light-chain, and biclonal) through a comprehensive screening process. Key predictors used in the model included MGUS isotype, monoclonal protein concentration, free light-chain ratio, and total concentrations of immunoglobulins (IgG, IgM, IgA). Bone marrow plasma cells were categorised as 0–4%, 5–9%, 10–14%, or ≥15% to assess the likelihood of SMM, with particular attention to cases where levels of these cells were ≥10%.
The results of the study are promising. The prediction model achieved a c-statistic of 0.85, indicating high accuracy in predicting SMM or more severe conditions. At a 10% predicted risk threshold for SMM, the model demonstrated a sensitivity of 86% and a specificity of 67%, with a positive predictive value of 32% and negative predictive value of 96%.
When compared to the Mayo Clinic’s risk stratification model, the new model showed a net benefit increase of 0.13 to 0.30 in making referral decisions for bone marrow sampling. However, researchers noted the need for external validation before widespread clinical adoption.
This model represents a significant advancement in managing MGUS and SMM, offering a more precise tool for clinicians to guide treatment decisions, and potentially sparing patients from unnecessary invasive bone marrow procedures.
Ada Enesco, EMJ
Reference
Eythorsson E et al. Development of a multivariable model to predict the need for bone marrow sampling in persons with monoclonal gammopathy of undetermined significance: a cohort study nested in a clinical trial. Ann Intern Med. 2024;177(4):449-457.
