Question:medium
A child was a victim of sexual assault, a test was done using a perianal swab. What's the name of this test (yellow needle-shaped crystals are seen)?
A child was a victim of sexual assault, a test was done using a perianal swab. What's the name of this test (yellow needle-shaped crystals are seen)?
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Yellow needle-shaped crystals from a semen swab come from spermine + picric acid \u2014 not a blood crystal test like Teichman or Takayama.
Updated On: Jun 22, 2026
- Barberio test
- Teichman test
- Takayama test
- Florence test
Show Solution
The Correct Option is A
Solution and Explanation
Work backwards from two clues in the question: the sample is being tested for semen, and the microscopy shows yellow needle-shaped crystals.
Clue 1 - it is a semen test: Among the four named tests, only Barberio and Florence are tests for semen; Teichman and Takayama are crystal tests for blood. That already narrows the field to A and D.
Clue 2 - the crystal colour and shape: Barberio's test uses picric acid, which combines with spermine present in semen to precipitate spermine picrate. These crystals are classically described as yellow and needle-shaped (rhombic/needle), exactly matching the image. Florence's test, by contrast, uses an iodine-potassium iodide reagent that reacts with choline to give dark-brown periodide crystals - brown, not yellow.
Confirm the eliminations: Teichman's test yields brown rhombic haemin crystals from blood; Takayama's test yields pink, feathery hemochromogen crystals from blood. Neither produces yellow needle-shaped crystals, and neither is a semen test.
Where it fits in the workup: Both Barberio and Florence are only presumptive/microchemical screening tests for semen; a positive Barberio (spermine picrate crystals) raises strong suspicion of seminal fluid but is still confirmed by demonstrating spermatozoa on microscopy and by acid-phosphatase estimation and modern DNA/PSA (p30) testing. In a child sexual-assault case the perianal swab is examined precisely because semen may be deposited there, and the chemical crystal test offers a rapid initial indication before confirmatory analysis.
Decision: Yellow needle-shaped crystals from a seminal-stain swab = spermine picrate = Barberio test.
$Answer = A\,(Barberio\ test)$
Clue 1 - it is a semen test: Among the four named tests, only Barberio and Florence are tests for semen; Teichman and Takayama are crystal tests for blood. That already narrows the field to A and D.
Clue 2 - the crystal colour and shape: Barberio's test uses picric acid, which combines with spermine present in semen to precipitate spermine picrate. These crystals are classically described as yellow and needle-shaped (rhombic/needle), exactly matching the image. Florence's test, by contrast, uses an iodine-potassium iodide reagent that reacts with choline to give dark-brown periodide crystals - brown, not yellow.
Confirm the eliminations: Teichman's test yields brown rhombic haemin crystals from blood; Takayama's test yields pink, feathery hemochromogen crystals from blood. Neither produces yellow needle-shaped crystals, and neither is a semen test.
Where it fits in the workup: Both Barberio and Florence are only presumptive/microchemical screening tests for semen; a positive Barberio (spermine picrate crystals) raises strong suspicion of seminal fluid but is still confirmed by demonstrating spermatozoa on microscopy and by acid-phosphatase estimation and modern DNA/PSA (p30) testing. In a child sexual-assault case the perianal swab is examined precisely because semen may be deposited there, and the chemical crystal test offers a rapid initial indication before confirmatory analysis.
Decision: Yellow needle-shaped crystals from a seminal-stain swab = spermine picrate = Barberio test.
$Answer = A\,(Barberio\ test)$
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