Iodine/Creatinine Ratio, Random, Urine
Use
Measurement of urinary iodine excretion provides the best index of dietary iodine intake. It is useful for assessing iodine toxicity or recent exposure using a random urine collection, and for monitoring iodine excretion rate as an index of replacement therapy. Urinary iodine is an essential marker for thyroid hormone production, and the iodine/creatinine ratio corrects for dilution effects in spot urine samples. Deficiency is indicated when concentrations fall below published thresholds and repeat testing may be recommended for confirmation.
Special Instructions
High concentrations of gadolinium- or iodine-containing contrast media may interfere; a specimen should not be collected for 96 hours after administration. A 24‑hour urine collection is preferred due to significant variation in excretion; random urine collection is acceptable. See “Metals Analysis Specimen Collection and Transport” for complete instructions.
Limitations
Use of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results. Random urine collections are less precise than 24‑hour collections and may require repeat sampling; reference ranges vary by age and sex and are not established for children <18 years.
New York Approved
Methodology
Mass Spectrometry (ICP-MS)
Biomarkers
LOINC Codes
- 55928-6
- 2161-8
- 55928-6
- 77202-0
- 2495-0
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
3 mL
Minimum Volume
2 mL
Container
Clean, plastic urine collection container; plastic, 10‑mL urine tube or clean plastic aliquot container with no metal cap or glued insert
Collection Instructions
Collect a random urine specimen; do not collect for 96 hours after gadolinium- or iodine‑containing contrast administration; see Metals Analysis Specimen Collection and Transport for complete instructions.
Patient Preparation
Avoid collection within 96 hours of administration of gadolinium‑ or iodine‑containing contrast media.
Causes for Rejection
All specimens will be evaluated for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 28 days |
| Frozen | 28 days |