Which laboratory method is used to detect urinary estrogen via a color reaction and yields pink on a positive result?

• A. Kober reaction
• B. Enzyme-linked immunosorbent assay
• C. Radioimmunoassay
• D. Mass spectrometry

Answer: (A)

The essential idea is a colorimetric test that visually signals the presence of estrogens in urine. The Kober reaction is a classic chemical color test where estrogen-containing compounds react with specific reagents under the assay conditions to form a pink-colored chromophore when estrogen is present. A positive result is indicated by this pink color, making it a straightforward direct color test for urinary estrogens.

This differs from the other methods: enzyme-linked immunosorbent assay relies on antibody–antigen interactions with a substrate that changes color, but the color produced is kit-dependent and not a characteristic pink signal of estrogen itself. Radioimmunoassay uses radioactive detection rather than a color change, and mass spectrometry detects compounds by their mass-to-charge ratios without any color readout.