Association of rubella and parvovirus B19 IgM positivity and suspected rheumatoid arthritis: a retrospective analysis from a large US national reference laboratory (2014-2023).

OBJECTIVE

Rubella and parvovirus B19 (B19V) infections can present with arthritis-like symptoms in adults instead of typical dermatological symptoms. We quantify associations between rubella and B19V, respectively, with arthritis-like complications using real-world diagnostic testing.

DESIGN

Cross-sectional and retrospective cohort study.

SETTING

Reference laboratories across the USA.

PARTICIPANTS

Participants with IgM tests for rubella (N=211 917) or B19V (N=644 473) performed at Labcorp from 2014 to 2023. Among these participants, participants with IgM tests for rubella (N=1867) or B19V (N=22 683) and longitudinal laboratory testing through Labcorp were followed for diagnostic tests for rheumatoid arthritis (RA) up to 1.5 years after the viral IgM tests.

PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcomes were arthritis-like suspicions by providers and diagnostic testing for RA-associated biomarkers.

RESULTS

Higher proportions of suspicions of arthritis (1.4%, p<0.001) and same-day RA-associated diagnostic testing (1.3%, p<0.001) and positivity (26.4%, p=0.003) were identified in rubella IgM-positive adults compared with rubella IgM-negative adults. A higher proportion of B19V IgM-positive adults had suspected arthritis (12.6%) compared with B19V IgM-negative adults (8.1%, p<0.001). While a higher proportion of B19V IgM-positive adults (21.3%) received RA-associated diagnostic testing compared with B19V IgM-negative adults (14.3%, p<0.001), a lower proportion of B19V IgM-positive adults with RA-associated diagnostic testing (12.8%) tested positive (B19V IgM-negative: 15.5%, p<0.001). There was a 33% increased risk of a suspected RA diagnosis in B19V IgM-positive participants compared with B19V IgM-negative participants (HR=1.33, 95% CI 1.10 to 1.61).

CONCLUSIONS

Increased awareness of non-typical RA symptoms may facilitate differential diagnosis between rubella, B19V and RA. Recent B19V infections do not occur concurrently with RA; recent B19V infections should be considered in the differential diagnosis for RA when patients present with polyarticular joint symptoms.