Abstract
The Watson-Schwartz test for urinary porphobilinogen (PBG) is generally characteristic for acute intermittent porphyria in relapse. The reaction is strong and unmistakable in patients with nervous or abdominal manifestations of the disease. Faint or borderline positive tests may be encountered in nonporphyric conditions, causing confusion in diagnosis. The additional use of butanol, which extracts all of the known Ehrlich aldehyde compounds except that of PBG, prevents such confusion. Pseudo-Ehrlich reactions, due to the hydrochloric acid in the reagent, are given by a number of compounds, including certain melanogens. A control with 22% hydrochloric acid must be carried out with each test.
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