Test Id : OSM24
Osmolality, 24 Hour, Urine
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessing the concentrating and diluting ability of the kidney using a 24-hour urine collection
Method Name
A short description of the method used to perform the test
Freezing Point Depression
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
24 Hour Osmo
24 HR Osmo
Specimen Type
Describes the specimen type validated for testing
Urine
Necessary Information
24-Hour volume (in milliliters) is required.
ORDER QUESTIONS AND ANSWERS
| Question ID | Description | Answers |
|---|---|---|
| TM02 | Collection Duration (h) | |
| VL02 | Volume (mL) |
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Supplies:
-Diazolidinyl Urea (Germall), 5.0 mL (T822)
-Urine Tubes, 10 mL (T068)
Container/Tube: 24-hour graduated urine container with no metal cap or glued insert
Specimen Volume: 10 mL
Collection Instructions:
1. Collect urine for 24 hours
2. Add 5 mL of diazolidinyl urea as preservative at start of collection or refrigerate specimen during and after collection.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Urine Preservative Collection Options
Note: The addition of preservative or application of temperature controls must occur at the beginning of the collection.
| Ambient (No additive) | No |
| Refrigerate (No additive) | Preferred |
| Frozen (No additive) | OK |
| 50% Acetic Acid | No |
| Boric Acid | No |
| Diazolidinyl Urea (Germall) | OK |
| 6M Hydrochloric Acid | No |
| 6M Nitric Acid | No |
| Sodium Carbonate | No |
| Thymol | No |
| Toluene | No |
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
1 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Ambient | 72 hours | ||
| Frozen | 14 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assessing the concentrating and diluting ability of the kidney using a 24-hour urine collection
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Osmolality is an index of the solute concentration. Urine osmolality is a measure of the concentration of osmotically active particles, principally sodium, chloride, potassium, and urea; glucose can contribute significantly to the osmolality when present in substantial amounts in urine. Urinary osmolality corresponds to urine specific gravity in nondisease states.
The ability of the kidney to maintain both tonicity and water balance of the extracellular fluid can be evaluated by measuring the osmolality of the urine either routinely or under artificial conditions. More information concerning the state of renal water handling or abnormalities of urine dilution or concentration can be obtained if urinary osmolality is compared to serum osmolality and urine electrolyte studies are performed. Normally, the ratio of urine osmolality to serum osmolality is 1.0 to 3.0, reflecting a wide range of urine osmolality.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-11 months: 50-750 mOsm/kg
> or =12 months: 150-1,150 mOsm/kg
Interpretation
Provides information to assist in interpretation of the test results
With normal fluid intake and normal diet, a patient will produce urine of about 500 to 850 mosmol/kg water. Above the age of 20 years, there is an age dependent decline in the upper reference range of approximately 5 mOsm/kg/year.
The normal kidney can concentrate urine to 800 to 1400 mosmol/kg and with excess fluid intake, a minimal osmolality of 40 to 80 mosmol/kg can be reached.
With dehydration, the urine osmolality should be 3 to 4 times the plasma osmolality
When a patient is drinking relatively large amounts of fluid the urine can be maximally diluted to approximately 100 mosmol/kg water.
A 24-hour urine osmolality will reflect the average urine osmolality over the day. Thus, a 24-hour urine osmolality will provide information regarding patient's ability to either dilute or concentrate the urine, and also their habitual water intake throughout the day in relation to their osmole intake. This information is most commonly used to determine if a patient with a risk of kidney stone disease is ingesting enough fluid to maintain a relatively dilute urine. Rough guidelines would suggest a treatment target of less than 400 mosmol/ kg water in a stone forming individual, which correlates with a total urine volume of greater than 2 L in an average individual.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Newman D, Price C. Renal function and nitrogen metabolites. In: Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 4th ed. WB Saunders Company; 2006
2. Delaney MP, Lamb EJ. Kidney disease. In. Rifai NF, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1306
Method Description
Describes how the test is performed and provides a method-specific reference
Measurement of the freezing point of urine is the most widely used principle in osmometers. The extent of lowering below 0 degrees C (the freezing point of water) is a function of the concentration of substances dissolved in the urine. By definition, 1 milliosmole per kilogram lowers the freezing point 0.001858 degrees C.(Schindler EI, Brown SM, Scott MG. Electrolytes and blood gases. In: Rifai N, Horwath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:610-612)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Sunday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
83935
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| OSM24 | Osmolality, 24 HR, U | 2694-8 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| UOS24 | Osmolality, 24 HR, U | 2694-8 |
| TM02 | Collection Duration (h) | 13362-9 |
| VL02 | Volume (mL) | 3167-4 |