Question:
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
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The Correct Option is A
Solution and Explanation
Step 1: Identify the analyte. In a sexual assault investigation a perianal swab is examined for seminal stains. The two classic crystal/microchemical tests for the presence of semen are the Florence test and the Barberio test, both of which target constituents of seminal fluid (Florence → choline; Barberio → spermine).
Step 2: Match the crystal description. The figure shows yellow, needle-shaped crystals. In the Barberio test, the seminal extract is treated with a saturated aqueous/alcoholic solution of picric acid; spermine in semen reacts to form spermine picrate, which appears as characteristic yellow, rhombic to needle-shaped crystals under the microscope. This matches the figure exactly, so the test is the Barberio test.
Step 3: Why the other options are wrong.
(B) Teichman test is a confirmatory test for blood: heating dried blood with glacial acetic acid and a halide produces rhombic, brown haemin (hematin) crystals - it detects blood, not semen, and the crystals are brown, not yellow.
(C) Takayama test is also a confirmatory crystal test for blood: it produces pink, feathery, needle/rhomboid hemochromogen (pyridine ferroprotoporphyrin) crystals - again a blood test, not a semen test, and pink in colour.
(D) Florence test detects choline in semen but gives dark brown, rhombic/needle-shaped periodide (choline-iodide) crystals with potassium iodide-iodine reagent. It is also only a presumptive (not confirmatory) test, and the crystals are brown, not yellow. Because the figure specifically shows yellow crystals, Barberio is preferred.
Final answer: A - Barberio test.
Step 2: Match the crystal description. The figure shows yellow, needle-shaped crystals. In the Barberio test, the seminal extract is treated with a saturated aqueous/alcoholic solution of picric acid; spermine in semen reacts to form spermine picrate, which appears as characteristic yellow, rhombic to needle-shaped crystals under the microscope. This matches the figure exactly, so the test is the Barberio test.
Step 3: Why the other options are wrong.
(B) Teichman test is a confirmatory test for blood: heating dried blood with glacial acetic acid and a halide produces rhombic, brown haemin (hematin) crystals - it detects blood, not semen, and the crystals are brown, not yellow.
(C) Takayama test is also a confirmatory crystal test for blood: it produces pink, feathery, needle/rhomboid hemochromogen (pyridine ferroprotoporphyrin) crystals - again a blood test, not a semen test, and pink in colour.
(D) Florence test detects choline in semen but gives dark brown, rhombic/needle-shaped periodide (choline-iodide) crystals with potassium iodide-iodine reagent. It is also only a presumptive (not confirmatory) test, and the crystals are brown, not yellow. Because the figure specifically shows yellow crystals, Barberio is preferred.
Final answer: A - Barberio test.
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