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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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Item Value
Available Stat? Yes
Test code LI
Performed by? Chemistry
Sendout? no
Price range $$
In House Availability Routine: 7 days;
STAT: 24 hours/ 7 days
Principle Lithium in the sample reacts with a substituted porphyrin compound at alkaline pH. A change in absorbance occurs which is directly proportional to the lithium concentration in the sample.
Interpretation The serum lithium level is not an accurate predictor of lithium toxicity. Chronic toxicity may occur with serum levels only slightly above the therapeutic range. In contrast, levels as high as 9.3 mmol/L without signs of intoxication have been described in acute overdose, when samples were collected during the distribution phase. Call the California Poison Control Center for guidance in the management of patients with possible chronic, acute, or acute imposed on chronic lithium toxicity. Their number is 1-800-8POISON.

Container type gold top gel tube
Amount to Collect 2 mL
Collection Instructions Urine cannot be accepted because of the variable potassium concentrations, which interfere with the methodology.
Sample type Blood
Special instructions Collect the sample at least 12 hrs after the last dose. Half-life is 15 -30 hrs. Lithium has a biphasic decline in the serum concentration/time curve.
Normal range
Therapeutic: 0.5 - 1.5 mmol/L
Borderline toxic: 1.5 mmol/L
Toxic: > 2.0 mmol/L

All values greater than 2.0 mmol/L are considered Critical Values and are called to the physician or patient care unit immediately.
Stability 5 days 2-8°C.
Interferences Plasma samples collected in tubes containing lithium heparin (green top) can result in a false increase in lithium concentration from the anticoagulant.

References 1. Dito, W.R.: Therapeutic Drug Monitoring - Lithium. Diagnostic Medicine, Jan/Feb 1980, p. 39.

2. Henry, J.B.: Clinical Diagnosis and Management by Laboratory Methods. 20th ed, WB Saunders Co, p. 356-357, 2001.

3. Infinity Lithium P1660040.05 Rev. Feb. 2003. ThermoTrace Noble Park, Victoria 3174 AUSTRALIA.

4. Olson KR ed. Poisoning & Drug Overdose, 3rd ed. Lange Clinical Manual. Appleton & Lange. Stamford, CT 06912-0041. 1999. Pgs 204-5.
CPT coding 80178
Last Updated 10/24/2012 11:52:32 AM
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