Test ID: RPOU
Phosphorus, Pediatric, Random, Urine
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Evaluation of hypo- or hyperphosphatemic states
Evaluation of patients with nephrolithiasis
A timed 24-hour urine collection is the preferred specimen for measuring and interpreting this urinary analyte. Random collections normalized to urinary creatinine may be of some clinical use in patients who cannot collect a 24-hour specimen, typically small children. Therefore, this random test is offered for children <16 years old.
Method Name A short description of the method used to perform the test
Molybdic Acid
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
PO4
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Plastic, 6-mL tube (Supply T465)
Specimen Volume: 5 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative.
Additional Information: A timed 24-hour urine collection is the preferred specimen for measuring and interpreting this urinary analyte. Random collections normalized to urinary creatinine may be of some clinical use in patients who cannot collect a 24-hour specimen, typically small children. Therefore, this random test is offered for children <16 years old.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Urine | Refrigerated (preferred) | 7 days |
| Ambient | 7 days | |
| Frozen | 7 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Approximately 80% of filter phosphorous is reabsorbed by renal proximal tubule cells. The regulation of urinary phosphorous excretion is principally dependent on regulation of proximal tubule phosphorous reabsorption. A variety of factors influence renal tubular phosphate reabsorption, and consequent urine excretion. Factors that increase urinary phosphorous excretion include high phosphorous diet, parathyroid hormone, extracellular volume expansion, low dietary potassium intake and proximal tubule defects (eg, Fanconi syndrome, X-linked hypophosphatemic rickets, tumor-induced osteomalacia). Factors that decrease, or are associated with decreases in, urinary phosphorous excretion include low dietary phosphorous intake, insulin, high dietary potassium intake, and decreased intestinal absorption of phosphorous (eg, phosphate-binding antacids, vitamin D deficiency, malabsorption states).
A renal leak of phosphate has also been implicated as contributing to kidney stone formation in some patients.
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.
No established reference values
Interpretation Provides information to assist in interpretation of the test results
Interpretation of urinary phosphorous excretion is dependent upon the clinical situation, and should be interpreted in conjunction with the serum phosphorous concentration.
| Pediatric Reference Ranges on a Random SpecimenPhosphate/Creatinine (mg/mg) | ||
| Age (year) | 5th Percentile | 95th Percentile |
| 0-1 | >0.34 | <5.24 |
| 1-2 | >0.34 | <3.95 |
| 2-3 | >0.34 | <3.13 |
| 3-5 | >0.33 | <2.17 |
| 5-7 | >0.33 | <1.19 |
| 7-10 | >0.32 | <0.97 |
| 10-14 | >0.22 | <0.86 |
| 14-17 | >0.21 | <0.75 |
Matos V, van Melle G, Boulat O et al: Urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in a healthy pediatric population. J Pediatr 1997;131:252-257
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Agarwal R, Knochel JP: Hypophosphatemia and hyperphosphatemia. In The Kidney. Sixth edition. Edited by Barry M Brenner. WB Saunders Company, Philadelphia, PA, 2000, pp 1071-1125
Method Description Describes how the test is performed and provides a method-specific reference
Inorganic phosphorus reacts with ammonium molydbdate in an acidic solution to form ammonium phosphomolybdate. The ammonium phosphomolybdate is quantified in the ultraviolet range (340 nm) (Package insert, Roche Phosphorus, Roche Diagnostics, Indianapolis IN).
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Sunday
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
84105
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| POCON | Phosphorus, Pediatric, Random, U | 2778-9 |
| CREA6 | Creatinine Concentration | 2161-8 |
| RATO5 | Phosphorus/Creatinine Ratio | 11141-9 |
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