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Test Name:
Iodine, Urine, 24-Hour
- SBMF No:
42202 - Performance Lab Name:
Mayo Medical Laboratories - Test Mnemonic:
U IODINE - ABN:
Required – Not FDA-Approved - CPT Code:
83789 - LOINC Code:
19146-0 - Ref Lab Test No:
9549 - Also Known As:
Iodide Excretion
Iodine Excretion
Urinary Free Iodide
Urinary Free Iodine - Also See:
42278 Iodine, Urine, Random - Spec Type:
Urine, 24-hour - Spec Container:
Plastic container with tightly fitting lid (no preservative) - Pref Vol:
10.0 mL aliquot from well mixed collection - Min Vol:
0.2 mL aliquot from well-mixed collection - Patient Prep:
If patient has been administered gadolinium-containing contrast media for radiographic studies wait at least 48 hours before starting urine collection - Spec Collect:
To begin collection of timed specimen, have patient urinate, noting date and exact time
Discard this first portion of urine, but document date and time of voiding on container label and test requisition as "start" of timed specimen
Save all urine voided during designated time period, including portion voided at exact end of time period
IMPORTANT: Refrigerate entire specimen (2-8°C) during and after collection to prevent bacterial growth
Document date and time of final voiding on label and requisition as "end" of timed specimen - Spec Process:
Upon completion of collection, mix entire specimen well and note 24-hour volume
Pour 10.0 mL of urine into separate plastic, trace metal-free container
Refrigerate urine aliquot and transport refrigerated
Send urine aliquot with notation of 24-hour urine volume on aliquot label and on requisition - Spec Store Transport:
Refrigerated preferred
Room temperature or frozen acceptable - Spec Remarks:
If this test is used in conjunction with the (131)I uptake test, then specimen collection should begin immediately after the dose of (131)I is given (ie, the patient should void and discard urine just prior to the (131)I, and all subsequent urine should be collected for the next 24 hours). The last void should be included in the collection.
High concentrations of gadolinium are known to interfere with most metals tests. If gadolinium-containing contrast media has been administered, a specimen should not be collected for 48 hours.
- Methodology:
Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) - Use:
Monitoring iodine excretion rate as an index of daily iodine replacement therapy
Correlating total body iodine load with (131)I uptake studies in assessing thyroid function - Clinical Significance:
Iodine is an essential element for thyroid hormone production. The measurement of urinary iodine serves as an index of adequate dietary iodine intake. - Reference Range:
0-15 years: Not Established
> or =16 years: 93-1125 mcg/specimen - Additional Test Info:
Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.
This test was developed and its performance characteristics determined by Laboratory Medicine and Pathology, Mayo Clinic. This test has not been cleared or approved by the U.S. Food and Drug Administration.
- Day Run:
Mon-Fri - Time Run:
5:00 pm - Time Reported:
2-5 days - Test Type:
CHEMISTRY
