Ehrlich's aldehyde test is used to confirm a diagnosis of acute intermittent porphyria.
Ehlich's aldehyde reagent consists of p-dimethyl amino benzaldehyde in acid solution.
Equal volumes of urine and Ehrlich's reagent are mixed. If a pink colour is formed this indicates a raised urinary concentration of either porphobilinogen or urobilinogen.
In cases of raised porphobilinogen, as in acute intermittent porphyria, the pink precipitate is observed to be insoluble in chloroform.