All of the following statements about Sabin-Feldman Dye test are true, except:
Correct Answer: Bluish staining of trophozoites indicates a positive test
Description: Sabin-Feldman dye test is a serological test method for diagnosis of Toxoplasmosis. The test is primarily based on detection of Tozoplasma-specific antibodies in the serum. The test is based on the specific inhibition of the staining of the trophozoites with alkaline methylene blue in the presence of anti-Toxoplasma antobodies. If anti-toxoplasma antibodies are present in the serum Toxoplasma trophozoites are not stained (Positive result) The Sabin-Feldman dye test The Sabin-Feldman dye test represent the first serological assay for diagnosis of toxoplasmosis The Sabin-Feldman dye test is based on the specific inhibition of the staining of the trophozoites with alkaline methylene blue in the presence of anti-Toxoplasma antibodies The test is based on the presence of ceain antibodies that prevent methylene blue dye from entering the cytoplasm of Toxoplasma organisms. The Sabin-Feldman dye test measures antibodies that render the membrane of living T.Gondii impermeable to methylene blue (no staining occurs) Patient serum is treated with Toxoplasma trophozoites and complements as activator, and then incubated. After incubation, methylene blue is added. If anti-toxoplasma antibodies are present in the serum If there are no anti-toxoplasma antibodies Toxoplasma trophozoites are not stained (Positive result) Trophozoites with intact membrane and appear blue under microscope (Negative result) Toxoplasma trophozoites propagated in mice peritoneal cavity is traditionally used The highest dilution of the test serum which inhibits the staining is the titer The test becomes positive within 1 or 2 weeks after injection and remains positive at low titers for years. Ref: Textbook of Medical Parasitology by Paniker; Medical parasitology by Arora and Arora 4th edition /94
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