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Acetaminophen

Item	Value
Test Update Information	Acetaminophen assay changed from the Abbott Axsym method to the Beckman DxC method on 6/25/2012.
Approval req'd?	No
Available Stat?	Yes
Test code	AAPH
Performed by	Parnassus Chemistry
In House Availability	Test available 24 hours per day 7 days per week
Method	Turbidimetric inhibition immunoassay (Beckman DxC800)
Container type	Gold top or Light Green top
Amount to Collect	1 mL blood
Sample type	Serum
Preferred volume	0.5 mL serum
Min. Volume	0.2 mL serum
Units	mg/L
Normal range	Therapeutic 10-20 mg/L Toxic > 150 mg/L (4 hours post ingestion)
Critical value	> 50 mg/L
Synonyms	Tylenol; Datril
Stability	Room temperature 8 hours, refrigerated 2 days, frozen 1 week
Turn around times	STAT 1 hour, Routine 1-3 days
Additional information	In suspected intoxication, at least 4 hours must have elapsed post-ingestion before a serum level can assist in determining the need to initiate N-acetylcysteine therapy; earlier levels are uninterpretable for this purpose. For additional emergency information, you may call the San Francisco regional poison center, 1-800-876-4766 (from UCSF dial 47-28600) Note: some monoclonal proteins may cause falsely low acetaminophen results. The presence of human anti-mouse antibodies or heterophile antibodies may also interfere with the acetaminophen assay in some cases. Testing for acetaminophen levels in parallel dilution studies and with a different assay may be useful in cases where interference by a monoclonal protein or abnormal immunoglobulin is suspected.
LOINC code	3298-7
Last Updated	6/20/2012 1:50:19 PM
Entry Number	5
Image caption	Nomogram: acetaminophen plasma concentration vs. time after acetaminophen ingestion (adapted from Rumack BH, Matthew H. Acetaminophen poisoning and toxicity. Pediatrics. 1975;55;871-876, with permission). The nomogram has been developed to estimate the probability of whether a plasma acetaminophen concentration in relation to the interval post ingestion will result in hepatotoxicity and, therefore, whether N-acetylcysteine therapy should be administered. CAUTIONS FOR USE OF THIS CHART: Time coordinates refer to time post ingestion. Graph relates only to plasma concentrations following a single, acute overdose ingestion. The Treatment Line is plotted 25% below the Rumack-Matthew Line to allow for potential errors in plasma acetaminophen assays and estimated time from ingestion of an overdose.
Image

If you have additional questions regarding this test, please call: 415-353-1667