Association between systemic immune-inflammatory markers and monoclonal gammopathy of undetermined significance in the elderly population: findings from the National health and nutrition examination survey

BACKGROUND: Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma cell disorder whose prevalence increases with age and may progress to multiple myeloma. The tumor microenvironment plays a crucial role in MGUS pathogenesis and progression. Systemic immune-inflammatory markers can reflect tumor microenvironment(TME) dynamics, but their association with MGUS odds remains understudied. METHODS: This cross-sectional study analyzed data from 12,080 adults aged ≥ 50 years (including 350 MGUS cases) in the National Health and Nutrition Examination Survey (NHANES III and 1999-2004 cycles). Multivariable logistic regression assessed associations between systemic immune-inflammatory markers [lymphocyte-to-monocyte ratio(LMR), Platelet-to-lymphocyte ratio(PLR), Hemoglobin, albumin, lymphocyte, platelet score(HALP), and their individual components] and MGUS. Generalized additive models identified nonlinear relationships and threshold effects across stratified groups. RESULTS: Higher LMR quartiles were positively associated with MGUS prevalence (Q4 vs. Q1: OR = 1.454, 95% CI 1.048-2.016), while elevated monocyte counts (OR = 0.624, 95% CI 0.456-0.853) and albumin levels (OR = 0.446, 95% CI 0.317-0.627) correlated with reduced MGUS odds. Nonlinear analysis revealed a U-shaped association between PLR and MGUS. There are race-specific nonlinear correlations involving LMR, PLR, and lymphocyte counts with MGUS. CONCLUSIONS: Systemic immune-inflammatory markers are significantly associated with MGUS odds in older adults, highlighting their potential for early detection and longitudinal monitoring.