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HelpTest Code IODCU Iodine/Creatinine Ratio, Random, Urine
Ordering Guidance
Due to the significant variation in the rate of secretion over the course of a day, a 24-hour collection is preferred. For more information see UIOD / Iodine, 24 Hour, Urine.
Specimen Required
Patient Preparation: High concentrations of gadolinium and iodine are known to interfere with most metal tests. If either gadolinium- or iodine-containing contrast media has been administered, wait a minimum of 96 hours before starting collection.
Supplies: Urine Tubes, 10 mL (T068)
Collection Container/Tube: Clean, plastic urine collection container
Submission Container/Tube: Plastic, 10-mL urine tube or a clean, plastic aliquot container with no metal cap or glued insert
Specimen Volume: 3 mL
Collection Instructions:
1. Collect a random urine specimen.
2. See Metals Analysis Specimen Collection and Transport for complete instructions.
Secondary ID
610708Useful For
Assessment of iodine toxicity or recent iodine exposure using a random urine collection
Monitoring iodine excretion rate as index of replacement therapy
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IODC | Iodine/Creat Ratio, U | No | Yes |
| CRETR | Creatinine, Random, U | No | Yes |
Special Instructions
Method Name
IODC: Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
CRETR: Enzymatic Colorimetric Assay
Reporting Name
Iodine/Creat Ratio, Random, USpecimen Type
UrineSpecimen Minimum Volume
2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 30 days | |
| Frozen | 30 days | ||
| Ambient | 14 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Iodine is an essential element for thyroid hormone production.
The measurement of urinary iodine is preferred for assessment of toxicity, recent exposure, and monitoring iodine excretion rate as an index of replacement therapy.
Reference Values
0-17 years: Not established
≥18 years: <584 mcg/g creatinine
Interpretation
Measurement of urinary iodine excretion provides the best index of dietary iodine intake and deficiency is generally indicated when the concentrations are below 100 mcg/L. For deficiency, 10 repeat random urines are recommended.
World Healthcare Organization (WHO) Criteria for Assessing Iodine Status
Children older than 6 years and adults
|
Median urinary iodine (mcg/L) |
Iodine intake |
Iodine status |
|
<20 |
Insufficient |
Severe deficiency |
|
20-49 |
Insufficient |
Moderate deficiency |
|
50-99 |
Insufficient |
Mild deficiency |
|
100-199 |
Adequate |
Adequate nutrition |
|
200-299 |
Above requirements |
May pose a slight risk of more than adequate |
|
>299 |
Excessive |
Risk of adverse health consequences |
Pregnant women
|
Median urinary iodine (mcg/L) |
Iodine intake |
|
<150 |
Insufficient |
|
150-249 |
Adequate |
|
250-499 |
Above requirements |
|
>499 |
Excessive |
Lactating women and children younger than 2 years
|
Median urinary iodine (mcg/L) |
Iodine intake |
|
<100 |
Insufficient |
|
>99 |
Adequate |
Cautions
Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.
Clinical Reference
1. Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023
2. Knudsen N, Christiansen E, Brandt-Christensen M, Nygaard B, Perrild H. Age- and sex-adjusted iodine/creatinine ratio. A new standard in epidemiological surveys? Evaluation of three different estimates of iodine excretion based on casual urine samples and comparison to 24 h values. Eur J Clin Nutr. 2000;54(4):361-363
3. Liberman CS, Pino SC, Fang SL, Braverman LE, Emerson CH. Circulating iodine concentrations during and after pregnancy. J Clin Endocrinol Metab. 1998;83(10):3545-3549
4. Pfeiffer CM, Sternberg MR, Schleicher RL, et al. CDC's Second National Report on Biochemical Indicators of Diet and Nutrition in the US Population is a valuable tool for researchers and policy makers. J Nutr. 2013;143(6):938S-947S
5. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry: Toxicological Profile for Iodine. HHS; 2004. Accessed June 29, 2023. Available at www.atsdr.cdc.gov/ToxProfiles/tp158.pdf
6. Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol. 2014;10(3):136-142. doi:10.1038/nrendo.2013.251
7. Beckford K, Grimes CA, Margerison C, et al. A systematic review and meta-analysis of 24-h urinary output of children and adolescents: impact on the assessment of iodine status using urinary biomarkers. Eur J Nutr. 2020;59(7):3113-3131. doi:10.1007/s00394-019-02151-w
Method Description
The metal of interest is analyzed by inductively coupled plasma mass spectrometry.(Unpublished Mayo method)
Day(s) Performed
Tuesday, Friday
Report Available
2 to 5 daysSpecimen Retention Time
14 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
83789
82570
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| IODCU | Iodine/Creat Ratio, Random, U | 55928-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CRETR | Creatinine, Random, U | 2161-8 |
| 614424 | Iodine Concentration Interpretation | 77202-0 |
| 614370 | Iodine Concentration | 2495-0 |
| 610709 | Iodine/Creat Ratio, U | 55928-6 |