Botulism/Lab Tests

MedicalTest{{#meta: itemprop="medicalWebPageAudiences" content="patient"}}{{#meta: itemprop="medicalWebPageSpecialities" content="cardiology"}}{{#meta: itemprop="medicalWebPageInfoTypes" content="symptoms,diagnosis,treatment,causes,prognosis,complications"}}

Overview

Botulism Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Botulism from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
CT
MRI
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Cost-Effectiveness of Therapy
Future or Investigational Therapies
Case Studies
Case #1
Botulism/Lab Tests On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Botulism/Lab Tests All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Botulism/Lab Tests
CDC on Botulism/Lab Tests
Botulism/Lab Tests in the news
Blogs on Botulism/Lab Tests
Directions to Hospitals Treating Botulism
Risk calculators and risk factors for Botulism/Lab Tests

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Seyedmahdi Pahlavani, M.D. [2], Keanu Ngo[3]

Overview

Botulism is a clinical diagnosis; laboratory testing is confirmatory and must never delay antitoxin therapy, because results may take several days. Confirmation rests on detection of botulinum neurotoxin (BoNT) or isolation of a toxin-producing clostridial species from serum, stool/enema, gastric contents, wound material, or the implicated food. Routine laboratory studies are typically normal and serve mainly to exclude alternative diagnoses. Testing is performed at state public health laboratories and the CDC; the state health department must be notified when botulism is suspected.

Specimen collection by clinical form

Collect specimens as soon as botulism is suspected and, when possible, before antitoxin administration:

• All forms: serum for toxin detection (a large volume is required, especially in infants).
• Foodborne: serum, stool (or enema effluent), gastric aspirate/vomitus, and all suspect foods.
• Infant/adult intestinal colonization: stool is the best specimen; if constipation prevents collection, give an enema of sterile, nonbacteriostatic water (not saline).
• Wound: serum plus wound exudate/tissue for anaerobic culture and toxin testing.

Confirmatory testing

Toxin detection

• Mouse bioassay (toxin neutralization): the reference-standard confirmatory assay; highly sensitive and specific, available only at specialized public health laboratories, but slow (results in several days) and requires laboratory animals.
• Endopep-MS (endopeptidase mass spectrometry): an in vitro assay detecting BoNT endopeptidase activity; validated for clinical specimens with a limit of detection equal to or better than the mouse bioassay and accurate serotype discrimination, now deployable in public health laboratories to improve turnaround (multicenter reproducibility 99.9%, correct-determination rate 99.4%).
• Immunoassays (ELISA-based): rapid; useful for food/environmental screening and increasingly for clinical serotyping, though sensitivity is antibody-dependent.

Serotype identification (by neutralization, Endopep-MS, or NAAT) guides epidemiologic response but should not delay treatment, which is empiric. Emerging endopeptidase, immunological, and molecular assays are not yet validated for all serotypes across complex clinical and environmental matrices, and standardized interpretive criteria remain to be established.

Culture and nucleic acid testing

• Culture: stool, wound, and food cultures require enriched selective media; isolation of toxigenic C. botulinum (or C. butyricum/C. baratii) in a symptomatic patient is diagnostic, as it is not normal flora. Culture yield is low in most hospital laboratories, which lack the expertise—send to public health laboratories.
• Nucleic acid amplification (NAAT/PCR): available at some reference laboratories to detect BoNT genes in clostridial isolates/cultures.

Diagnostic yield and timing

Yield is form-dependent and often low; a negative result does not exclude botulism:

• Serum toxemia is detectable in ~70% of foodborne and wound cases (pooled toxemia-review estimate) but far less often in infant botulism; the pooled estimate is ~28%, whereas U.S. series report positivity in only ~1%–13%.
• In foodborne disease, combined serum/stool toxin detection confirms ~46% of clinically diagnosed cases and stool culture is positive in ~70% (single-review figures).
• Serum toxin can persist for >10–16 days after onset; stool organism/toxin can persist for weeks to months (up to ~5 months in infants).

Ancillary laboratory studies (to exclude mimics)

• Routine labs: generally normal; mild dehydration may occur in infants from poor feeding. No characteristic CBC or chemistry abnormality.
• Cerebrospinal fluid: typically normal; a mildly elevated protein was reported in only ~13% of a 332-case series—helping distinguish botulism from the albuminocytologic dissociation of Guillain-Barré syndrome.
• Edrophonium (Tensilon) test: typically negative in botulism (positive in myasthenia gravis), a potential bedside discriminator when the diagnosis is uncertain; note that edrophonium is no longer widely available (FDA diagnostic approval withdrawn) and an occasional positive response can occur in botulism.
• Toxicology: targeted testing when the differential includes drug/toxin exposure; not a routine confirmatory step for botulism.

Electrodiagnostic studies (summary)

Electrodiagnostic testing is the most useful ancillary study when the diagnosis is uncertain. Characteristic findings are low resting CMAP amplitudes with post-exercise facilitation and an incremental response to high-frequency (20–50 Hz) repetitive nerve stimulation—the most distinctive finding; needle EMG may show brief, small-amplitude motor unit potentials. Sensitivity declines in the post-acute phase, and a normal study does not exclude botulism. Detail is provided in Other diagnostic studies.

Clinically actionable points

• Treat on clinical suspicion; do not await laboratory confirmation.
• Collect serum before antitoxin, plus stool/enema (sterile water, not saline), gastric contents, wound material, and suspect foods as applicable.
• Notify the state health department/CDC early to arrange testing and antitoxin.
• A normal CSF supports (does not exclude) botulism and helps distinguish it from GBS.

Gallery

• 
  Clostridium botulinum on egg yolk agar showing the lipase reaction (72 h). From Public Health Image Library (PHIL).
• 
  Clostridium botulinum spores stained with malachite green. From PHIL.
• 
  Clostridium botulinum type A colonies on blood agar (24 h). From PHIL.
• 
  Clostridium botulinum type E colonies with opaque zone on egg yolk agar (48 h). From PHIL.

References

Template:WikiDoc Sources

Related Pages

• Signs Detected:
• Drug Interactions:
• Used To Diagnose:Botulism
• Uses Device: