In addition to treponemal infections, the following can produce a positive (biologically false-positive) reagin test result: Systemic infections unrelated to syphilis (such as tuberculosis, rickettsial diseases, and endocarditis) Immunization (specifically COVID-19 or smallpox vaccines) Systemic lupus erythematosus Antiphospholipid antibody syndromes Pregnancy Cerebrospinal fluid (CSF) reaginic tests are reasonably sensitive for early disease but less so for late neurosyphilis.