Precipitin test
Definition
A species-confirmation test that adds species-specific antiserum to a stain extract; a visible precipitate forms only when the target protein is present. Developed by Paul Uhlenhuth (1901) and still used as a confirmatory test for human blood.
- Developed
- By Paul Uhlenhuth in 1901
- Method
- Antibody-antigen reaction that produces an insoluble precipitate
- Forensic use
- Species-confirmation of biological material, especially human blood
Common questions
What does a precipitin test do in forensic serology?+
The test identifies what species a biological stain came from. You add species-specific antiserum to a stain extract. If the right protein is present, antibodies bind to it and form a visible precipitate (a solid clump). Only the correct species produces this reaction.
How is the precipitin test used as a confirmatory test?+
Once a stain is suspected to be human blood, the precipitin test confirms it by using human-specific antiserum. A positive result (precipitate forms) confirms the blood is human. It remains a standard confirmatory method in modern forensic labs.
Why is the precipitin test still relevant today?+
Despite being over a century old, it is still used as a confirmatory test because it is reliable, inexpensive, and gives a clear visible result. It works well alongside modern DNA testing to verify the biological origin of evidence.
Related terms
- ABO system
- The blood-group classification described by Karl Landsteiner in 1901: groups A, B, AB, and O, defined by antigens on red-cell surfaces and...
- Antiserum (pl. antisera)
- Blood serum from an animal (typically a rabbit) that has been immunised against the proteins of another species. It contains antibodies that...
- Double immunodiffusion (Ouchterlony)
- A gel-based assay in which both the antigen (test sample) and the antibody (antiserum) diffuse toward each other from separate wells cut...
- Forensic serology
- The branch of forensic science concerned with detecting and characterising biological fluids (blood, semen, saliva, vaginal secretions) as evidence in legal proceedings,...
- Lateral-flow immunoassay
- A rapid, card-based test in which a stain extract wicks through a membrane past antibody-conjugate zones; a visible line forms within minutes...
- Precipitin arc / line
- The visible band of precipitate in an Ouchterlony plate where diffusing antigen and diffusing antibody meet. Its shape and relationship to adjacent...
- Presumptive test
- A fast, low-cost, class-specific screen used to triage a caseload before instrumental work begins. Examples are Marquis reagent for opioids and amphetamines,...
- Ring precipitin test
- A tube-based precipitin assay in which the antiserum is carefully underloaded beneath the sample; a ring of precipitate at the interface indicates...
- Secretor status
- About 80% of people secrete ABH blood-group antigens into body fluids such as saliva and semen. Secretor status was historically used to...
- Spur formation
- In Ouchterlony, a spur is formed when one arc curves beyond another due to an excess of a cross-reacting but non-identical antigen....
Explained in these topics
- Scope and History of Forensic SerologyA species-confirmation test that adds species-specific antiserum to a stain extract; a visible precipitate forms only when the target protein is present. Devel...
- Species of Origin: Precipitin and Ouchterlony TestsAny test in which antibodies form an insoluble precipitate with their corresponding antigens. In forensic serology, precipitin tests use species-specific antis...