Test ID: EFP
Electrolytes, Random, Feces
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
The work-up of cases of chronic diarrhea
Making the diagnosis of factitial diarrhea
The relationship, osmolality equals 2 x (sodium + potassium), is the basis for this evaluation.
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| UOSMF | Osmolality, F | Yes | Yes |
| NAF | Sodium, Random, F | Yes | Yes |
| KF | Potassium, Random, F | Yes | Yes |
| CLF | Chloride, Random, F | Yes | Yes |
| MGF | Magnesium, Random, F | Yes | Yes |
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
UOSMF/9258: Freezing Point Depression
NAF/8374, KF/8375, MGF/81345: Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES)
CLF/8467: Coulometric Titration
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
Cl (Chloride)
Electrolytes, Feces
Fecal Electrolytes
Magnesium (Mg)
Mg (Magnesium)
Osmolality, Feces
Potassium, Feces
Sodium, Feces
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: Stool container (Supply T291)
Specimen Volume: 20 g
Collection Instructions:
1. Collect a very liquid stool specimen.
2. See Stool Collection Information Sheet in Special Instructions.
Additional Information:
1. Do not send formed stool. In the event a formed stool is submitted, the test will not be performed. The report will indicate "A formed stool specimen was submitted for analysis. This test was not performed because it only has clinical value if performed on a watery stool specimen."
2. High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen must not be collected for 96 hours.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | Formed stool |
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 |
|---|---|---|
| Fecal | Frozen (preferred) | 14 days |
| Refrigerated | 48 hours |
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:
-The normal daily dietary intake of electrolytes
-Electrolytes are passively transported from serum and other vascular spaces to equilibrate fecal osmotic pressure with vascular osmotic pressure
-Exogenous substance and rare toxins (cholera toxin) cause electrolyte transport into fecal water
Fecal osmolality is normally in equilibrium with vascular osmolality, and sodium is the major affecter of this equilibrium. Fecal osmolality is normally 2 x (sodium + potassium) unless there are exogenous factors inducing a change in this ratio, such as the presence of other osmotic agents (magnesium sulfate, saccharides), or drugs inducing secretions, such as phenolphthalein or bisacodyl.
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.
CHLORIDE
0-15 years: not established
> or =16 years: 0-39 mEq/kg
MAGNESIUM
0-15 years: not established
> or =16 years: 0-199 mEq/kg
OSMOLALITY
0-15 years: not established
> or =16 years: 220-280 mosmol/kg
POTASSIUM
0-15 years: not established
> or =16 years: 0-199 mEq/kg
SODIUM
0-15 years: not established
> or =16 years: 0-159 mEq/kg
Interpretation Provides information to assist in interpretation of the test results
A useful formula is 2 x (stool sodium + stool potassium)=stool osmolality + or - 30 mOsm/kg. Typically, stool osmolality is similar to serum since the gastrointestinal tract does not secrete water.
Osmotic Diarrhea:
If the measured osmolality exceeds the calculation of 2 x (sodium + potassium) by >30 mEq/kg, an osmotic gap exists indicating osmotic diarrhea. Fecal potassium concentration and daily excretion rate are usually below the median level in patients with osmotic diarrhea. Modest increases (2x) in fecal chloride concentration and excretion rate may be observed when fecal sodium is elevated in association with osmotic diarrhea. Osmotic agents such as magnesium, sorbitol, or polyethylene glycol may be the cause of this. Magnesium concentration of >200 mEq/kg is frequently associated with decreased fecal sodium and potassium and is an indicator of excessive consumption of magnesium, a common cause of osmotic diarrhea.
Secretory Diarrhea:
Increased fecal sodium and chloride content or daily excretion rate with normal fecal potassium and no osmotic gap indicates secretory diarrhea. If sodium concentration or 24-hour sodium excretion rate is 2 to 3 times normal and osmotic gap >30 mOsm/kg, secretory diarrhea is also indicated. Agents such as phenolphthalein, bisacodyl, or cholera toxin should be suspected.
An osmotic gap >100 mOsm/kg indicates factitial diarrhea, likely due to magnesium or phenolphthalein consumption.
For very low stool osmolality, consider factitial diarrhea.
Normal or low fecal sodium in association with high fecal potassium suggests deterioration of the epithelial membrane or a bleeding lesion
High sodium and potassium in the absence of an osmotic gap indicate active electrolyte transport in the gastrointestinal tract that might be induced by agents such as cholera toxin or hypersecretion of vasointestinal peptide.
Fecal chloride concentration or daily excretion rate are markedly elevated (7-10 times normal) in association with congenital hypochloremic alkalosis with chloridorrhea.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Correct interpretation requires that the stool specimen submitted be a watery stool.
In the event a soft or formed stool is submitted, the test will not be performed, and the report will indicate: "A formed stool specimen was submitted for analysis. This test was not performed because it only has clinical value if performed on a watery stool specimen."
Bacterial action on insoluble carbohydrates in feces will cause an artifactual increase in the fecal water content of electrolytes. The specimen should be stored and shipped frozen to avoid this artifactual increase.
High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen must not be collected for 96 hours.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Phillips S, Donaldson L, Geisler K, et al: Stool composition in factitial diarrhea: a 6-year experience with stool analysis. Ann Intern Med 1995;123:97-100
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
Method Description Describes how the test is performed and provides a method-specific reference
See individual test descriptions.
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 Friday; 5 p.m.
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.
82438-Chloride
83735-Magnesium
84302-Sodium
84999 x 2-Osmolality and potassium (see CPT Coding in Special Instructions)
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 |
|---|---|---|
| 9258 | Osmolality, F | 2693-0 |
| 32299 | Chloride, Random, F | 2076-8 |
| 32304 | Potassium, Random, F | 25506-7 |
| 32290 | Magnesium, Random, F | 26708-8 |
| 32300 | Sodium, Random, F | 14055-8 |
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