Bloodstream Infection and Risk for Plasma Cell Neoplasms: A Population-Based Cohort Study.

Background: Invasive infection may be the first prompt to investigate the occult presence of a plasma cell neoplasm. The objective of this study was to quantify the risk for subsequent diagnosis of a plasma cell neoplasm following bloodstream infection (BSI).

Methods: Statewide population-based surveillance was conducted from January 1 2000 - December 31 2019. Statewide databases were used to identify patients with incident plasma cell neoplasms diagnosed within 1-year following a BSI diagnosis.

Results: A cohort of 90 individuals who had BSI within the year preceding diagnosis of plasma cell neoplasm and 95 753 patients with BSI without this malignancy were included. The time to diagnose a plasma cell neoplasm was a median 123 (31-221) days after index BSI. The overall incidence of plasma cell neoplasms among those with incident BSI was 93.9 per 100 000 population annually. Among the study population, development of a BSI was associated with a 13-fold increased risk for diagnosis of plasma cell neoplasm (IRR; 12.9; 95% CI, 10.3-15.8; p < 0.001). The increased risk following BSI was elevated for both sexes, with a magnitude of risk higher for females (IRR; 14.0; 95% CI, 9.8-19.4). Streptococcus pneumoniae BSI was associated with the highest risk for subsequent diagnosis of a plasma cell neoplasm (IRR 46.9; 95% CI; 26.2-77.4).

Conclusions: The presence of a BSI, particularly with S. pneumoniae, is a marker for occult plasma cell neoplasms in a small but significant number of patients. Further studies are warranted to identify occult neoplastic disease investigation strategies for patients with incident BSIs.