Test Catalog

Test Id : POU_F

Phosphorus, Feces

Useful For
Suggests clinical disorders or settings where the test may be helpful

Workup of cases of chronic diarrhea

 

Identifying the use of phosphate-containing laxatives contributing to osmotic diarrhea

Method Name
A short description of the method used to perform the test

Photometric, Ammonium Molybdate

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Phosphorus, F

Specimen Type
Describes the specimen type validated for testing

Fecal

Ordering Guidance

This test is only clinically valid if performed on watery specimens. In the event a formed fecal specimen is submitted, the test will not be performed.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: No barium, laxatives, or enemas may be used for 96 hours prior to start of, or during, collection.

Supplies: Stool containers - 24, 48, 72 Hour Kit (T291)

Container/Tube: Stool container

Specimen Volume: 10 g

Collection Instructions: Collect a very liquid stool specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

5 g

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

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
Fecal Frozen (preferred) 14 days
Refrigerated 7 days
Ambient 48 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Workup of cases of chronic diarrhea

 

Identifying the use of phosphate-containing laxatives contributing to osmotic diarrhea

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The concentration of electrolytes in fecal water and their rate of excretion are dependent upon 3 factors:

-Normal daily dietary intake of electrolytes

-Passive transport from serum and other vascular spaces to equilibrate fecal osmotic pressure with vascular osmotic pressure

-Electrolyte transport into fecal water due to exogenous substances and rare toxins (eg, cholera toxin)

 

Fecal osmolality is normally in equilibrium with vascular osmolality, and sodium is the major effector of this equilibrium. Fecal osmolality is normally 2 x (sodium + potassium) unless there are exogenous factors inducing a change in composition, such as the presence of other osmotic agents (magnesium sulfate, saccharides) or drugs inducing secretions, such as phenolphthalein or bisacodyl. Osmotic diarrhea is caused by ingestion of poorly absorbed ions or sugars.(1) There are multiple potential causes of osmotic diarrhea. Measurement of phosphate and/or magnesium in liquid stool can assist in identifying intentional or inadvertent use of magnesium and/or phosphate-containing laxatives as the cause.(2-4) The other causes of osmotic diarrhea include ingestion of osmotic agents such as sorbitol or polyethylene glycol laxatives, or carbohydrate malabsorption due most commonly to lactose intolerance. Carbohydrate malabsorption can be differentiated from other osmotic causes by a low stool pH (<6).(5,6)

 

Non-osmotic causes of diarrhea include bile acid malabsorption, inflammatory bowel disease, endocrine tumors, and neoplasia.(1) Secretory diarrhea is classified as non-osmotic and is caused by disruption of epithelial electrolyte transport when secretory agents such as anthraquinones, phenolphthalein, bisacodyl, or cholera toxin are present. The fecal fluid usually has elevated electrolytes (primarily sodium and chloride) and a low osmotic gap (<50 mOsm/kg). Infection is a common secretory process; however, it does not typically cause chronic diarrhea (defined as symptoms >4 weeks).

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.

An interpretive report will be provided

Interpretation
Provides information to assist in interpretation of the test results

Phosphorus elevation above 102 mg/dL is suggestive of phosphate-induced diarrhea.(4)

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Phospholipids contained in liposomal drug formulations (eg AmBisome) may be hydrolyzed in the test due to the acidic reaction pH and thus lead to elevated phosphate results.(1,2)

 

In very rare cases, gammopathy, in particular type IgM (Waldenstrom macroglobulinemia), may cause unreliable results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Steffer KJ, Santa Ana CA, Cole JA, Fordtran JS: The practical value of comprehensive stool analysis in detecting the cause of idiopathic chronic diarrhea. Gastroenterol Clin North Am. 2012;41:539-560

2. Ho J, Moyer TP, Phillips SF: Chronic diarrhea: the role of magnesium. Mayo Clin Proc. 1995;70:1091-1092

3. Fine KD, Santa Ana CA, Fordtran JS: Diagnosis of magnesium-induced diarrhea. N Engl J Med. 1991;324:1012-1017

4. Fine KD, Ogunji F, Florio R, Porter J, Ana CS: Investigation and diagnosis of diarrhea caused by sodium phosphate. Dig Dis Sci. 1998;43(12):2708-2714

5. Eherer AJ, Fordtran JS: Fecal osmotic gap and pH in experimental diarrhea of various causes. Gastroenterology. 1992;103:545-551

6. Casprary WF: Diarrhea associated with carbohydrate malabsorption. Clin Gastroenterol. 1986;15:631-655

Method Description
Describes how the test is performed and provides a method-specific reference

In the presence of sulfuric acid, inorganic phosphate and ammonium molybdate form an ammonium phosphomolybdate complex. The concentration of phosphomolybdate formed is measured photometrically and is directly proportional to the inorganic phosphate concentration.(Package insert: Roche Phosphorus reagent. Roche Diagnostics; V9.0 12/2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

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, Thursday

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.

1 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

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 Regional Manager. 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 modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

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.

84100

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports