Amatoxin Toxicity Workup

Updated: May 18, 2023
  • Author: Douglas S Lee, MD; Chief Editor: Stephen L Thornton, MD  more...
  • Print

Approach Considerations

Evaluation of the potentially amatoxin poisoned patient requires a high index of suspicion in the appropriate patient population and will be based primarly on history and physical with laboratory analysis primarly serving to confirm clinical suspicion.


Laboratory Studies

Various laboratory studies may be indicated in patients with suspected amatoxin poisoning. [14]

Abnormalities in electrolyte, glucose, blood urea nitrogen (BUN), and creatinine levels may be due to vomiting, diarrhea, and dehydration. Progression to renal failure causes a further rise in BUN and creatinine levels. Glucose levels should be monitored very closely in patients with hepatic failure.

Because hepatic damage is the main concern with amatoxin poisoning, liver function tests (LFTs) should be performed, including the following:

LFT results may be normal upon presentation; however, elevation may occur after 24-48 hours.

The prothrombin time (PT), the activated partial thromboplastin time (aPTT), or both should be evaluated. Severe coagulopathy may develop as the toxicity progresses to later stages. PT is considered a reliable prognostic indicator for Amanita poisoning.

Urinalysis is indicated, with hematuria and proteinuria signifying renal involvement. Microscopic hematuria may occur in stage I. Oliguria and anuria develop with renal failure. According to a pilot study, urinary amanitin analysis may have high specificity and positive predictive value, but it is not clinically feasible in most cases.  Amatoxins may be detected in the urine prior to the onset of symptoms but are only detectable for a short time. [15]

Because A phalloides can directly induce pancreatitis, amylase and lipase levels should be measured.

Leves of amatoxin and other cyclopeptides in serum or urine are not routinely obtained and have no clinical utility. 


Radiography, Ultrasonography, and CT

Specific diagnostic imaging studies are not indicated with a history of amatoxin ingestion. Mushrooms are not radiopaque and thus will not be seen on abdominal radiographs. However, in the absence of such a history, abdominal radiography may be performed if bowel obstruction or ileus appears in the differential diagnosis.

Ultrasonography and computed tomography (CT) scanning may be considered for the purpose of narrowing the differential diagnosis, but they do not yield positive findings.


Analysis of Mushroom Specimen

Meixner test

If a specimen of the ingested mushroom is available for analysis, the Meixner test can be performed. This test can detect amatoxin concentrations as low as 0.2 mg/mL; however, the number of false-negative and false-positive test results (eg, from the presence of psilocybin) reported raises questions about its reliability in clinical use.

Uneaten mushrooms should be placed in a dry paper bag for transport. A drop of liquid from a fresh mushroom is expressed onto a lignin-containing paper (ie, paper derived from wood pulp, such as newspaper but not filter paper). After the paper has dried, a drop of concentrated hydrochloride (10-12 N) is added. If amatoxins are present, a blue color develops within 2 minutes. Delayed appearance of a blue color suggests that amatoxin is present but in lower concentrations.

A dried mushroom may be tested by crushing it in pure methanol and using a drop of the methanol before adding the hydrochloride. It should be kept in mind that gastric contents are not suitable for the Meixner test; the results will not be valid.

The Meixner test should never be used to rule in or out a potential amatoxin mushroom ingestion.

Spore analysis in stomach contents

An experienced mycologist may analyze and identify spores in gastric contents. The spores can be examined by light microscopy using an oil immersion lens after isolation and concentration via centrifuge. The spores are examined in both water and Melzer solution. The spores of amatoxin-containing Amanita mushrooms are smooth and turn blue in Melzer solution.

Whether the spores of Amanita species survive the digestive process and pass into the stool is unknown.


Other Tests

Radioimmunoassay, thin-layer chromatography, and high-performance liquid chromatography can measure the toxin in the serum, although these methods are generally not available. Amatoxins are eliminated very rapidly from the serum. Levels have no prognostic significance.

On histologic analysis, excised livers from patients with Amanita poisoning reveal massive hepatic centrilobular necrosis with resultant hemorrhage. If allowed to progress, the poisoning causes lobular collapse and regenerative changes.