Ring Precipitation Test- Principle, Procedure, Results, Examples

  • Interactions of antibodies and antigens, in the form of various tests, have been developed to determine the presence or absence of antibodies or antigens in a sample. 
  • A type of interaction between soluble antigens with its specific antibody in a suitable medium that results into the formation of an insoluble complex that precipitates is termed as precipitation reaction.
  • The ring test or the precipitin ring test is a simple serological technique that illustrates the precipitin reaction in solution.

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Objectives of Ring Precipitation Test

  1. To detect antigen-antibody complexes.
  2. Describe the circumstances under which antigen-antibody complexes precipitate out of solution.
  3. Detect antibodies in patient serum which can be used to diagnose disease.

Principle of Ring Precipitation Test

The precipitin ring assay is a quick qualitative test for the presence of antigen–antibody complexes. It is based on the principles of the precipitin curve which states that antigen-antibody interact forming cross-linked precipitate when the proper ratio of antigen to antibody is reached. A solution containing the antiserum to be investigated is placed in the bottom of a series of clear test tubes. Solutions containing increasing concentrations of a known antigen are gently layered above the antibody solution. If the test antiserum contains antibody recognizing the antigen, immune complexes will form and be visible as a whitish ring at the interface. The white ring demonstrated is the formation of visible precipitate, a flocculent or granular turbidity, in the test fluid.

Semi-quantitative results can be obtained by comparing the experimental results to those derived from a standard curve constructed using known quantities of antigen and antibody.

Procedure of Ring Precipitation Test

  1. Test antiserum is introduced into a small diameter test tube.
  2. Clear solution of test antigen is then carefully added to form a distinct upper layer. Antigen of different concentrations can be used for subsequent tubes in series.
  3. After 4 hours incubation, the formation of a ring of precipitate at the interface of two liquid layers is checked for.
  4. The rate at which the visible ring forms depends on the concentration of the antigen.
  5. For titre determination of antibodies, different dilutions of antiserum can be used.
  6. The highest dilution with a visible ring is used to determine the titer. The titer is the reciprocal of the highest dilution showing a positive result, expressed as a whole number.

Results Interpretation of Ring Precipitation Test

Results Interpretation of Ring Precipitation Test

Positive Result

Development of a white ring at the junction of antiserum and antigen solution indicates positive test.

Negative Result

Absence of a ring formation.


C-reactive protein (CRP), Lancefield grouping of β-haemolytic streptococci, Ascoli’s thermoprecipitin test for anthrax diagnosis are the examples of the ring test.


  1. Lydyard, P.M., Whelan,A.,& Fanger,M.W. (2005).Immunology (2 ed.).London: BIOS Scientific Publishers.
  2. Owen, J. A., Punt, J., & Stranford, S. A. (2013). Kuby Immunology (7 ed.). New York: W.H. Freeman and Company.
  3. Playfair, J., & Chain, B. (2001). Immunology at a Glance. London: Blackwell Publishing.
  4. Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.
  5. http://ecoursesonline.iasri.res.in/mod/page/view.php?id=61673
  6. http://fac.ksu.edu.sa/sites/default/files/lab_6_ring_test.pdf
  7. https://courses.lumenlearning.com/microbiology/chapter/detecting-antigen-antibody complexes/

About Author

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Sagar Aryal

Sagar Aryal is a microbiologist and a scientific blogger. He is doing his Ph.D. at the Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal. He was awarded the DAAD Research Grant to conduct part of his Ph.D. research work for two years (2019-2021) at Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Saarbrucken, Germany. Sagar is interested in research on actinobacteria, myxobacteria, and natural products. He is the Research Head of the Department of Natural Products, Kathmandu Research Institute for Biological Sciences (KRIBS), Lalitpur, Nepal. Sagar has more than ten years of experience in blogging, content writing, and SEO. Sagar was awarded the SfAM Communications Award 2015: Professional Communicator Category from the Society for Applied Microbiology (Now: Applied Microbiology International), Cambridge, United Kingdom (UK). Sagar is also the ASM Young Ambassador to Nepal for the American Society for Microbiology since 2023 onwards.

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