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Test Code LITH Lithium, Serum

Useful For

Monitoring therapy of patients with bipolar disorders, including recurrent episodes of mania and depression

 

Evaluating lithium toxicity

Method Name

Colorimetric

Reporting Name

Lithium, S

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Draw blood 8 to 12 hours after last dose (trough specimen).

2. Serum gel tubes should be centrifuged within 2 hours of collection.

3. Red-top tubes should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.

Additional Information: Peak serum concentrations do not correlate with symptoms.


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject

Clinical Information

Lithium alters the intraneuronal metabolism of catecholamines by an unknown mechanism. It is used to suppress the manic phase of manic-depressive psychosis.

 

Lithium is distributed throughout the total water spaces of the body and is excreted primarily by the kidney.

 

Toxicity from lithium salts leads to ataxia, slurred speech, and confusion. Since the concentration of lithium in the serum varies with the time after the dose, blood for lithium determination should be drawn at a standard time, preferably 8 to 12 hours after the last dose (trough values).

Reference Values

Therapeutic: 0.5-1.2 mmol/L (trough concentration)

Critical value: >1.6 mmol/L

There is no relationship between peak concentration and degree of intoxication.

Interpretation

The therapeutic range for lithium has been established at 0.5 to 1.2 mmol/L. Within this range, most people will respond to the drug without symptoms of toxicity. However, response and side effects are individual. Lithium concentrations and side effects can increase with the loss of salt and water from the body, which can occur with a salt-free diet, excessive sweating, or an illness that causes vomiting and diarrhea. A variety of prescribed drugs, over-the-counter medications, and supplements can also increase, decrease, or interfere with the concentrations of lithium.

Cautions

No significant cautionary statements

Method Description

Colorimetric test. Lithium present in the sample reacts with a substituted porphyrin compound at an alkaline pH, resulting in a change in absorbance which is directly proportional to the concentration of lithium in the sample.(Package insert: Roche Lithium reagent, Roche Diagnostic Corp, Indianapolis, IN)

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

80178

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LITH Lithium, S 14334-7

 

Result ID Test Result Name Result LOINC Value
LITH Lithium, S 14334-7