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Test Code ACTMN Acetaminophen LAB43

Important Note

Human anti-mouse antibodies (hama) may be present in samples from patients who have received immunotherapy or diagnostic procedures utilizing monoclonal antibodies or in individuals who have been regularly exposed to animals. Additionally, other heterophile antibodies, such as human anti-goat antibodies may be present in patient samples. Manufacturers formulate assays to minimize the effects of these antibodies; however careful evaluation of patient results must be done when patients are known to have such antibodies.

Test Method

Particle Enhanced Turbidimetric Inhibition Immunoassay; Beckman


Monday through Sunday

Routine: Typically completed within 4 hours after arrival at the
testing site.

Expedite: Typically completed within 2 hours after specimen
arrives at the testing site.

STAT: Typically completed within 1.5 hours after specimen
arrives at the testing site.

Useful For

Monitoring toxicity in overdose cases, Serum concentration and
half-life are the only way to assess degree of intoxication in
early stages since other liver function studies (eg, bilirubin,
liver function enzymes) will not show clinically significant
increases until after tissue damage has occurred, at which point
therapy is ineffective.

Specimen Requirement

0.5 mL lithium heparin serum or plasma is required.

CPT Code Information

Insurances following Medicare rules: G0480

80329 Analgesics, non-opioid; 1 or 2

Reference Values

Therapeutic: 10-30 mcg/mL

  • Critical Value: > 40 mcg/mL

Post-ingestion Evaluation:

  • Peak levels are reached between 30 and 60 minutes after oral
  • Overdose cases: the specimen is drawn 4 hours after the time of
    suspected ingestion.
  • Elimination (half-life) Determination: In addition to
    monitoring acetaminophen blood levels with respect to time
    post-ingestion for evaluation of potential hepatoxicity,
    elimination rate (half-life) of 2 to 3 hours is normal and not
    associated with toxic damage to the liver. Acetaminophen levels as
    low as 50 mcg/mL may be toxic when the half-life reaches 12 hours.
    Half-life determination may be particularly useful in instances
    where time of ingestion is not known and in following response to
    therapy. Half-life can be determined by obtaining acetaminophen
    levels at two accurately timed intervals at least 2 hours

LOINC Code Information

3298-7 Acetaminophen [Mass/Volume] In Serum Or Plasma

Additional Specimen Collection Information

Serum red-top tube or lithium heparin plasma green-top tube is
acceptable. For overdose cases: the specimen is collected 4 hours
after the time of suspected ingestion. Serum and plasma gel tubes
are NOT acceptable. Serum or plasma should be separated from
contact with cells within 2 hours of collection. Refrigerate
specimen if unable to assay within 8 hours of collection.