The Meixner test in the detection of alpha-amanitin and false-positive reactions caused by psilocin and 5-substituted tryptamines.

Michael Beuhler, David C Lee, Richard Gerkin

Index: Ann. Emerg. Med. 44(2) , 114-20, (2004)

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Abstract

The Meixner test has been suggested to identify the presence of alpha-amanitin, one of the toxic compounds in Amanita mushrooms. We attempted to determine the detection limit of the Meixner test for alpha-amanitin and to determine the percentage of positive sample interpretation compared with other mushroom indole compounds.This was a 2-part in vitro experiment. In part 1, we applied the Meixner test to a series of dilutions of alpha-amanitin (0 microg, 0.8 microg, 1.0 microg, 2.0 microg, and 4.0 microg) on telephone book paper, which were then presented to 5 blinded emergency physicians. We sought to determine the lowest amount of alpha-amanitin that was universally recognized as positive by the physicians (the detection limit). In the second part, 5 emergency physicians were presented simultaneously with 10 Meixner processed samples, including the mushroom indole compounds alpha-amanitin (2 microg and 10 microg), psilocin (20 microL and 60 microL of mushroom extract), 5-hydroxytryptamine (100 microg and 200 microg), and 5-methoxy-N,N-dimethyltryptamine (100 microg and 200 microg), as well as 2 negative controls (20 microL of water and methanol). We determined how likely these other indoles are to be mistaken for a positive alpha-amanitin Meixner reaction result by determining the percentage of positive sample interpretation for each compound and comparing them with the rate for alpha-amanitin. Fisher's exact test was used to determine any significant difference (P<.05) between the samples.The minimum amount of alpha-amanitin that was identified with 100% agreement by testers was 2 microg. For the second part, there was 100% agreement that psilocin gives a positive Meixner test (100% false positive) and a 35% recognition rate of the 5-substituted tryptamine compounds as a positive Meixner test. There was no statistical difference between the interpretation of alpha-amanitin and psilocin, suggesting the test is unable to differentiate between them.Although the Meixner test has a good detection limit for toxic amounts of alpha-amanitin, a positive Meixner reaction does not adequately distinguish between alpha-amanitin and other mushroom indoles.