Common infectious agents and monoclonal B-cell lymphocytosis: a cross-sectional epidemiological study among healthy adults

Risk factors associated with monoclonal B-cell lymphocytosis (MBL), a potential precursor of chronic lymphocytic leukaemia (CLL), remain unknown. Using a cross-sectional study design, we investigated demographic, medical and behavioural risk factors associated with MBL. "Low-count" MBL (cases) were defined as individuals with very low median absolute count of clonal B-cells, identified from screening of healthy individuals and the remainder classified as controls. 452 individuals completed a questionnaire with their general practitioner, both blind to the MBL status of the subject. Odds ratios (OR) and 95% confidence interval (CI) for MBL were estimated by means of unconditional logistic regression adjusted for confounding factors. MBL were detected in 72/452 subjects (16%). Increasing age was strongly associated with MBL (P-trend