ROSE BENGAL

Results should always be interpreted together with clinical evaluation, epidemiological exposure, disease stage, immune status and other diagnostic procedures.

Brucellosis diagnosis should not rely on a single laboratory result. Whenever possible, serology should be interpreted together with culture, molecular methods, follow-up samples and clinical findings.

Early samples may be negative because antibodies may not yet be detectable. If clinical suspicion remains high, a second sample should be obtained 14–21 days later and tested in parallel with the first sample to assess seroconversion.

A negative serological result does not always exclude brucellosis, particularly in early infection, localized disease or immunosuppressed patients.

Rose Bengal is a rapid and sensitive screening test, but it should be confirmed by additional bacteriological or serological methods such as BRUCELLACAPT®, ELISA or VIRCLIA®.

Rose Bengal detects agglutinating antibodies and may produce false-negative results in localized or prolonged disease when non-agglutinating antibodies predominate.

False-positive Rose Bengal results may occur in people living in endemic areas, in individuals with previous Brucella infection, or in infections caused by bacteria sharing common LPS epitopes with Brucella.

IgM is useful for acute forms of brucellosis, but low IgM levels may occasionally persist for more than 12 months after infection. IgM should not be interpreted alone.

For IgM ELISA testing, human IgG sorbent must be used to avoid possible false-positive results due to rheumatoid factor or false-negative results due to excess IgG antibodies.

ELISA and VIRCLIA® IgG/IgM assays provide useful information for routine diagnosis, but they do not by themselves differentiate past exposure from active infection in high-prevalence areas.

BRUCELLACAPT® titres higher than 1/320 suggest brucellosis, but results should always be evaluated according to clinical evidence and local seroprevalence.

In endemic areas, lower BRUCELLACAPT® titres may be encountered and require cautious interpretation.

In positive BRUCELLACAPT® titres of 1/5120, additional serum dilutions should be tested, especially when the assay is used for patient follow-up.

A decrease in BRUCELLACAPT® titres may support patient recovery when accompanied by clinical improvement, but serological follow-up should not be used as the only criterion of cure.

Serological assays do not indicate the site of infection and are not intended to replace culture or direct diagnostic techniques.