The implications of Rose Bengal test seroconversion in the diagnosis of brucellosis in children in an endemic region

Background: The Rose Bengal test (RBT) is a commonly used simple serological test for brucellosis. We assessed brucellosis in individuals <18 years for RBT performance; duration of RBT positivity following infection; and potential factors associated with RBT seroconversion timing. Methods: The medical files of first hospital admissions of brucellosis, 2005–2014, southern Israel, were retrospectively reviewed. Results: Overall, RBT was positive in 99% of 416 primary brucellosis admissions. The mean age was 9.8 ± 4.5 years; all patients were of Bedouin ethnicity. Of 273 patients with subsequent RBT testing, RBT remained positive in 169 cases (duration range: 0.1–122 months). Overall, 104 patients had subsequent negative RBT result (duration range: 0.9–127; median: 29.9 months). Comparing fast (<30 months) vs. slow (≥30 months) seroconversion, IgM titres ≥1:640 were more common in fast seroconversion episodes (53% vs. 23%, p =.003). Anaemia was more common in the slow seroconversion group (76% vs. 52%, p =.02). Age, gender, ethnicity, fever, arthralgia, thrombocytopenia, leukopenia, liver enzymes, bacteraemia and adequate treatment rates were similar. Conclusions: RBT positivity rate in first hospital visit was high. Fast negative seroconversion was associated with high IgM titres and lower anaemia rates at first presentation. These findings may assist early recognition of long-lasting brucellosis patients in endemic regions.