Iodine, Urine

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General Information

Lab Name
Lab Code
650
External Test Id
ICRU, IODCU
Description

Useful For:

  • Assessment of iodine toxicity or recent exposure in a 24-hour urine collection
  • Monitoring iodine excretion rate as index of replacement therapy

Note: Due to the significant variation in the rate of secretion over the course of a day, a 24-hour collection is preferred. If a random urine specimen is submitted, the iodine/creatinine ratio will be performed.

Synonyms
IODCU, UIOD, Urinary Free Iodine, Urinary Iodine
Components

Interpretation

Method

Iodine, 24 Hour Urine: Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Iodine/Creatinine Ratio, Random Urine: Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Enzymatic Colorimetric Assay

Reference Range
Ref. Range Notes

Iodine, 24 Hour Urine Reference Values:

  • 0-17 years: Not Established
  • >/= 18 years: 75-851 mcg/24 hour

Iodine/Creatinine Ratio Reference Values:

  • 0-17 years: Not Established
  • >/= 18 years: <584 mcg/g creatinine
Interferences and Limitations

Cautions: Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.

Ordering & Collection

Specimen Type
Urine
Collection

Patient Preparation:

  1. High concentrations of gadolinium and iodine are known to interfere with most metal tests. If gadolinium- or iodine-containing contrast media has been administered, wait a minimum of 96 hours before starting collection.
  2. 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 dose, and all subsequent urine should be collected for the next 24 hours). The last void should be included in the collection.

Collection:

  • Timed: Collect urine for 24 hours in a sage pour-spout urine container. Refrigeration during collection is preferred. Refrigerate specimen within 4 hours of completion of 24-hour collection.
  • Random:

Note: May be collected with 50% Acetic Acid preservative.

Handling Instructions

Outside Laboratories:

  • 24-Hour:
    • Mix specimen well. Measure and record total volume. Document total volume and collection interval on the requisition.
    • Transfer 10 mL urine to a screw-cap, plastic aliquot container with no metal cap or glued insert. Refrigerate urine.
  • Random: transfer urine to a screw-cap, plastic aliquot container with no metal cap or glued insert and refrigerate.
Quantity
Requested: Timed: 10 mL urine; Random: 3 mL urine
Minimum: Timed: 0.3 mL urine; Random: 2 mL urine

Processing

Receiving Instructions
  • 24-Hour:
    • Mix specimen well. Measure and record total volume. Document total volume and collection interval on the requisition.
    • Transfer 10 mL urine to a screw-cap, plastic aliquot container with no metal cap or glued insert. Refrigerate urine.
  • Random: transfer urine to a screw-cap, plastic aliquot container with no metal cap or glued insert and refrigerate.

Login: SEND1-;REFRIG

Timed Collection:

  • RSNDT1: MAYOSD
  • RSTYP1: URN-;24 hr, TV (insert volume)
  • RTSRQ1: ;Iodine, Urine (Mayo Test UIOD)

Random Urine Collection:

  • RSNDT1: MAYOSD
  • RSTYP1: URN-RAND
  • RTSRQ1: ;Iodine/Creatinine Ratio, Random Urine (Mayo Test IODCU)

Sendouts, order Mayo Test:

  • UIOD for Timed/24 hour collections. Note the collection interval and total volume in the MayoAccess order.
  • IODCU for random collections.

Stability:

  • 24 Hour Urine: Refrigerated (preferred): 146 days; Frozen: 146 days; Ambient: 146 days
  • Random Urine: Refrigerated (preferred): 30 days; Frozen: 30 days; Ambient: 14 days
Misc Sendout

Performance

Lab Department
Frequency
Performed: Monday, Wednesday, Friday. Report Available: 1-3 days.
Available STAT?
No
Performing Location(s)
Sendout Mayo Clinic Laboratories (Superior Drive)
800-533-1710

3050 Superior Drive NW
Rochester, MN 55901

Billing & Coding

Billing Comments

CPTs:

  • Iodine, 24 hour urine: 83789
  • Iodine/Creatinine Ratio for Random Urine: 83789, 82570