Rose Bengal plate test (RBT) for Brucella: Principle, Procedure and limitation

Rose Bengal plate test

The Rose Bengal test (RBT) is a simple, rapid slide-type agglutination assay performed with a stained B. abortus suspension at pH 3.6–3.7 and plain serum.

Although the overall sensitivity reported for RBT varies widely, with the use of good quality antigens made by experienced or reference laboratories, the sensitivity of RBT can increased.

Rose Bengal plate test
Rose Bengal plate test

It is often used as a screening test in human brucellosis and would be optimal for small laboratories with limited means.  False-negative reactions occur especially in the early stages of acute infection.

Procedure of Rose Bengal Plate Test:

  1. Test Serum (0.03 ml) is mixed with an equal volume of antigen on a white tile or enamel plate to produce a zone approximately 2 cm in diameter.
  2. The mixture is agitated gently for four minutes at ambient temperature, and then observed for agglutination.
  3. Any visible reaction is considered to be positive.
Proposed use of RBT in the diagnosis of human brucellosis and complementary tests
Proposed use of RBT in the diagnosis of human brucellosis and complementary tests

Limitation of Rose Bengal Test:

  1. Low sensitivity particularly in long evolution (chronic) cases, and relatively low specificity in endemic areas.
  2. Moreover, some authors consider that prozones make strongly positive sera appear as negative in RBT.

The test is very sensitive and positive samples should be checked by the Complement fixation test (CFT) or by an IgG specific procedure such as ELISA. The RBT can be used in all animal species but positive results should be confirmed by a quantitative test.

About Acharya Tankeshwar 458 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.


  1. Please send me information on how I can obtain brucellosis test kits : Rose Bengal; Complement Fixation Test; and ELISA

  2. Hello, my dad is a veternerian and there was this screening for brucellosis done by govt using RBPT, and it turned out to be postive….but he got the test done in a private lab and it turned out negative for Igg….so what r we supposed to do

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