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Test Code LAB43 Acetaminophen, Reflex to Repeat

Useful For

Monitoring toxicity in overdose cases

Profile Information

Test Code Test Name Methodology

Available

Separately

Always

Performed
LAB43 Acetaminophen Enzyme Immunoassay No Yes

Testing Algorithm:

If the inital acetaminophen test result is abnormal (≥ 5 ug/mL), one additional acetaminophen test will automatically be reflexed.  The timed reflex test is scheduled to be collected 4 hours from the initial test result entry.

Reflex Tests

Test Code Test Name

Available

Separately

Always

Performed
N/A Lab Only-Acetaminophen Repeat No No

Performing Laboratory

Bozeman Health Laboratory Services

Specimen Requirements

Specimen Type: Plasma or serum
Container/Tube: Light-green top (lithium heparin gel), red top, or gold top

Specimen Volume: 1 mL
Specimen Minimum Volume: 0.5 mL

Specimen Transport Temperature

Ambient <24 hours/Refrigerated >24 hours

Specimen Stability

Specimen Type Temperature Time
Plasma or Serum Ambient 24 hours
  Refrigerated 7 days
  Frozen 6 months

Reference Values

Reference Range: <5 ug/mL

Therapeutic concentration: 10-30 µg/mL
Toxic concentration (automatic call-back): >150 µg/mL

Additional Information

  • The normal half-life for acetaminophen is less than 4 hours, while the toxic half-life is greater than 4 hours.
  • The toxic level is dependent on half-life. When the half-life is 4 hours, hepatotoxicity generally will not occur unless the concentration is above 150 µg/mL. The level at which toxicity occurs decreases with increasing half-life until it is encountered at values as low as 50 µg/mL when the half-life reaches 12 hours.
  • For half-life determination, draw 2 specimens at least 4 hours apart and note the exact time of each draw. Half-life can be calculated from the concentrations and the time interval.
  • First specimen should be drawn no sooner than 2 hours post-ingestion.
  • Therapeutic acetaminophen concentrations vary significantly depending on the individual patient. A range of 10 µg/mL to 30 µg/mL may be an effective specimen concentration for many patients; however, some individuals are best treated at concentrations outside this range. The physician must determine the appropriate therapeutic range for each patient.

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

80302(x2)