The internist Kurt Hoesch (1890 - 1966) first published the detection of porphobilinogen in urine in 1947. The test named after him is used as a screening method for acute hepatic porphyria (Gressner 2019).
The Schwartz-Watson test mentioned below was developed by the Americans Cecil J Watson (1901 - 1983) and Samuel Schwartz (1916 - 1997) and is also used to detect porphobilinogen (Gressner 2017).
The Hoesch test is used to detect increased levels of porphobilinogen (PBG) in urine (Herold 2018). Increased levels of PBG are found in acute intermittent porphyria (Ostendorf 2017).
Up to < 1.77 mg / g or < 0.88 mmol / mol porphobilinogen can be found in spontaneous urine. In collected urine, the values are < 1.70 mg / 24 h or < 7.5 µmol / 24 h (Arndt 2017).
The Hoesch test is primarily used to exclude or detect acute forms of hepatic porphyria. The test can also be used to differentiate between hereditary or toxic (e.g. lead poisoning, as lead inhibits the synthesis of porphobilinogen [Merz 2024]) porphyrin metabolism disorders (Arndt 2017).
In the Hoesch test, 2 drops of fresh urine are added to 2 - 3 ml of Ehrlich aldehyde reagent (Herold 2018).
If the solution turns red, the test is positive, i.e. the urine contains an increased amount of porphobilinogen (Herold 2018).
The sensitivity of the test is similar to that of the Schwartz-Watson test, but the specificity is significantly higher, although exact figures are lacking (Gressner 2019).
Values of > 100 μmol / l indicate hereditary, autosomal dominant acute hepatic porphyria. Values of > 1,000 µmol / 24 h are found in acute clinical symptoms (Arndt 2017).
These can occur, for example, in alcohol-induced malnutrition and can be triggered by indole-3-acetic acid, alpha-methyldopa and phenazopyridine hydrochloride (Ostendorf 2017).
The Schwartz-Watson test is another method for detecting porphobilinogen in urine (Gressner 2017).
PBG is a pyrrole derivative and thus a precursor of porphyrins (Arndt 2017).