Sabin–Feldman dye test

{{Short description|Serologic test for diagnosing toxoplasmosis}}

{{Infobox diagnostic

| name = Sabin–Feldman dye test

| image =

| alt =

| caption =

| pronounce =

| synonyms =

|purpose = diagnose for toxoplasmosis.

| reference_range =

| calculator =

| DiseasesDB =

| ICD10 =

| ICD9 =

| ICDO =

| MedlinePlus =

| eMedicine =

| MeshID =

| OPS301 =

| LOINC =

}}

A Sabin–Feldman dye test is a serologic test to diagnose for toxoplasmosis. Patient serum is treated with Toxoplasma trophozoites and complement, and then incubated. After incubation, methylene blue is added. If anti-Toxo antibodies are present in the serum, the antibody-antigen complex activates complement to lyse the parasite membrane, Toxoplasma trophozoites are not stained (positive result); if there are no antibodies, trophozoites with intact membrane are stained and appear blue under microscope (negative result).

The dilution of the test serum at which 50% of the tachyzoites are thin, distorted and colorless is reported as antibody titer of the test serum.

The test is highly sensitive and specific with no false positives reported so far.{{huh|date=March 2020}}

Drawbacks of this test:

1. Difficulty in maintaining the live tachyzoites.

2. It detects immunoglobulin G(IgG) antibodies, hence cannot differentiate between recent or past infection.

3.False positive for Sarcocystis, Trypanosoma lewisi, Trichomonas vaginalis{{huh|date=March 2020}}