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

Study objective The Meixner test has been suggested to identify the presence of α-amanitin, one of the toxic compounds in Amanita mushrooms. We attempted to determine the detection limit of the Meixner test for α-amanitin and to determine the percentage of positive sample interpretation compared with other mushroom indole compounds. Methods This was a 2-part in vitro experiment. In part 1, we applied the Meixner test to a series of dilutions of α-amanitin (0 μg, 0.8 μg, 1.0 μg, 2.0 μg, and 4.0 μg) on telephone book paper, which were then presented to 5 blinded emergency physicians. We sought to determine the lowest amount of α-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 α-amanitin (2 μg and 10 μg), psilocin (20 μL and 60 μL of mushroom extract), 5-hydroxytryptamine (100 μg and 200 μg), and 5-methoxy-N,N-dimethyltryptamine (100 μg and 200 μg), as well as 2 negative controls (20 μL of water and methanol). We determined how likely these other indoles are to be mistaken for a positive α-amanitin Meixner reaction result by determining the percentage of positive sample interpretation for each compound and comparing them with the rate for α-amanitin. Fisherʹs exact test was used to determine any significant difference (P<.05) between the samples. Results The minimum amount of α-amanitin that was identified with 100% agreement by testers was 2 μg. 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 α-amanitin and psilocin, suggesting the test is unable to differentiate between them. Conclusion Although the Meixner test has a good detection limit for toxic amounts of α-amanitin, a positive Meixner reaction does not adequately distinguish between α-amanitin and other mushroom indoles.