Which of the following is a qualitative screening test for porphobilinogen to aid in porphyrias diagnosis?

Which of the following is a qualitative screening test for porphobilinogen to aid in porphyrias diagnosis?

• A. Caraway test
• B. Gutmann test
• C. Jendrassik-Grof test
• D. Watson-Schwartz test

Answer: (D)

This item is testing knowledge of a qualitative urine screening method for porphobilinogen to help diagnose porphyrias. The Watson-Schwartz test is designed for this purpose. It uses Ehrlich’s reagent, which forms a colored complex with porphobilinogen. To distinguish PBG from other Ehrlich-reactive substances in urine, the mixture is partitioned between two solvents (commonly butanol and chloroform). Porphobilinogen preferentially moves into the butanol layer, so a persistent color in that organic layer indicates the presence of porphobilinogen. This makes it a simple, qualitative screen to raise suspicion of porphyrias, with positive results prompting confirmatory testing and clinical correlation. The other tests listed are not the standard qualitative screening for porphobilinogen.

This item is testing knowledge of a qualitative urine screening method for porphobilinogen to help diagnose porphyrias. The Watson-Schwartz test is designed for this purpose. It uses Ehrlich’s reagent, which forms a colored complex with porphobilinogen. To distinguish PBG from other Ehrlich-reactive substances in urine, the mixture is partitioned between two solvents (commonly butanol and chloroform). Porphobilinogen preferentially moves into the butanol layer, so a persistent color in that organic layer indicates the presence of porphobilinogen. This makes it a simple, qualitative screen to raise suspicion of porphyrias, with positive results prompting confirmatory testing and clinical correlation. The other tests listed are not the standard qualitative screening for porphobilinogen.