Diagnostic accuracy of urinary amanitin in suspected mushroom poisoning: a pilot study.

Background: Amatoxin-containing species are responsible for the most severe cases of mushroom poisoning, with high mortality rate. Therefore, this poisoning should be ruled out in all patients presenting gastrointestinal symptoms after wild mushroom ingestion.

Objective: To determine sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic efficacy (DE) of urinary amanitin analysis in cases of suspected mushroom poisoning.

Methods: All cases of mushroom ingestion referred to a Poison Center during a one-month period were analyzed. Amanitin measurements were performed by ELISA method (functional least detectable dose 1.5 ng/ml; cut-off value not clearly established). Gastrointestinal symptoms latency and initial clinical assessment were considered alternative diagnostic tools. Definitive diagnosis was used as the reference standard.

Results: Among 61 patients included in the study, amatoxin poisoning was diagnosed in 10 cases. Urine samples were collected 5.5 to 92 hours after mushroom ingestion. Urinary amanitin DE was 91.8%, 93.4%, and 80.3%, based on the cut-off value considered (1.5, 5.0, and 10.0 ng/ml, respectively). Symptoms latency longer than 6 hours and initial clinical assessment DE were 70.5% and 67.2%, respectively. To identify amatoxin poisoning, initial clinical assessment resulted more sensitive and urinary amanitin analysis more specific.

Conclusions: Urinary amanitin analysis is a valuable diagnostic tool and may significantly contribute to the management of suspected mushroom poisoning. At present, the best diagnostic accuracy can be obtained taking advantage of both the high sensitivity and negative predictive value of the clinical assessment performed by an experienced toxicologist, and the high specificity and positive predictive value that characterize urinary amanitin analysis.