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Test ID: Acetamnphn Lvl
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Acetaminophen Level
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Useful For
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Quantitative determination of acetaminophen overdose in serum and plasma; to determine risk of liver damage and to help monitor the outcome of antidote treatment.
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Method name and description
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The assay is based on a homogeneous enzyme immunoassay technique used for the quantitative analysis of acetaminophen in human serum or plasma on the Roche cobas c-systems. It is based on competition between drug in the sample and drug labeled with the enzyme glucose‑6‑phosphate dehydrogenase (G6PDH) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD+) to NADH, resulting in an absorbance change that is measured spectrophotometrically. Endogenous serum G6PDH does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.
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Clinical information
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Acetaminophen is a widely used analgesic and antipyretic found in a number of over‑the‑counter and prescription products. When consumed in overdose quantities, acetaminophen may cause severe liver and kidney damage, or death. (Roche Cobas TDM Acetaminophen Gen.2 package insert).
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Specimen type / Specimen volume / Specimen container
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Specimen type : Serum , Plasma
Minimum volume of sample: 1 mL
Serum: Plain Tube ( red or yellow top without gel seperator)
Plasma: Lithium heparinized (without gel seperator)
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Collection instructions / Special Precautions / Timing of collection
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Collect blood by standard venipuncture techniques as per specimen requirements. When processing samples in primary tubes (sample collection systems), follow the instructions of the tube manufacturer.
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Storage and transport instructions
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Storage: 24 hours at Room Temperature
7 days at 2 – 8°C;
6 months at ‑20 °C
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed, icteric and lipemic samples, wrong collection container, insufficient sample.
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Biological reference intervals and clinical decision values
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Therapeutic range: 66-199 umol/L
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Factors affecting test performance and result interpretation
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The concentration of acetaminophen in serum or plasma depends on the time of drug ingestion; concomitant drug therapy; sample condition; time of sample collection; and individual variations in absorption, distribution,biotransformation, and excretion.
Alcoholics are at risk for toxicity at lower doses. Enhanced susceptibility to toxic effects have also been reported in persons receiving long‑term anticonvulsant therapy and patients taking isoniazid.
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
STAT: 1 hour
Routine: One working day
Specimen Retention: 4 days
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