Sabin-Feldman dye test - UK NEQAS For Microbiology

for parasitology
Sabin-Feldman dye test
The Sabin-Feldman dye test was first described in 19481. The test measures the total amount of
antibody in serum which is capable of complement mediated killing of toxoplasma tachyzoites.
Serum is diluted across a microtitre plate and the end point is the dilution at which 50% of the
tachyzoites are dead. Results are expressed in international units/ml relative to a standard
reference serum provided by the National Institute of Biological Standards and Control. The dye
test is highly sensitive and fully quantitative. Results can range from 2 - >4000 iu/ml with a normal
range of 2 – 125 iu/ml. The dye test is the gold standard test of toxoplasma serology2 but the
requirement for live tachyzoites, cultured in animals, has restricted use to specialist Reference
Laboratories. The development of cell culture methods which can reliably provide tachyzoites for
the dye test3 provides the opportunity for the test to be more widely available.
The dye test is the reference test for the NEQAS scheme 2. This is particularly important when
detecting low concentrations of antibody which can cause problems for participants because the
results are close to test thresholds. Comparison with the dye test makes users aware of the
characteristics of their tests; the need for confirmatory testing in clinical samples and the limitations
of different tests in different patient groups.
References
1. Sabin AB, Feldman HA (1948). Dyes as microchemical indicators of a new immunity
phenomenon affecting a protozoan parasite (Toxoplasma) Science 108, 660-3.
2. Reiter-Owana I, Petersen E, Joynson D et al (1999). The past and present role of the
Sabin-Feldman dye test in the serodiagnosis of toxoplasmosis. Bull World Health
Organisation, 77(11), 929-935.
3. Chatterton JMW, Evans R, Ashburn D at el (2002). Toxoplasma gondii in vitro culture for
experimentation. Journal of Microbiological Methods 51, 331-335.

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