Test Id : A1AFS
Alpha-1-Antitrypsin Clearance, Feces and Serum
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosing protein-losing enteropathies
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 |
|---|---|---|---|
| AATS | Alpha-1-Antitrypsin, S | No | Yes |
| A1ATF | Alpha-1-Antitrypsin, 24 Hr, F | No | Yes |
Method Name
A short description of the method used to perform the test
Nephelometry
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
a-1-Antitrypsin, F&S
A1A
AAT (Alpha-1-Antitrypsin)
Alpha 1 Antitrypsin
Alpha 1 Antitrypsin (A1A) Clearance, Feces and Serum
Anti-Alpha-1-Trypsin
Antitrypsin Fecal Clearance
Intestinal Clearance of Alpha-1-Antitrypsin
Specimen Type
Describes the specimen type validated for testing
Fecal
Serum
Ordering Guidance
The recommended procedure for protein-losing enteropathy is A1AFS / Alpha-1-Antitrypsin Clearance, Feces and Serum.
Shipping Instructions
Feces and serum should be shipped together. Specimens shipped separately may delay testing.
ORDER QUESTIONS AND ANSWERS
| Question ID | Description | Answers |
|---|---|---|
| HOURS | Hours |
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Both feces and serum are required. Blood must be drawn during the stool collection period.
Specimen Type: Serum
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top or serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial
Specimen Type: Feces
Supplies: Stool Containers - 24, 48, 72 Hour Kit (T291)
Container/Tube: Stool container
Specimen Volume: Entire collection
Collection Instructions:
1. Collect a 24-hour fecal collection.
2. If no specimen is obtained within 24 hours, extend collection time to 48 to 72 hours. Document duration.
Forms
If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Test Request (T728) with the specimen.
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.
Homogenized feces: 1 mL; Serum: 0.5 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Gross icterus | OK |
| Feces collected in any preservative or fixative | Reject |
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 | |
| Ambient | 14 days | ||
| Refrigerated | 14 days | ||
| Serum | Frozen (preferred) | 28 days | |
| Ambient | 28 days | ||
| Refrigerated | 28 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosing protein-losing enteropathies
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Alpha-1-antitrypsin (AAT) is a 54-kDa glycoprotein that is resistant to degradation by digestive enzymes and is, therefore, used as an endogenous marker for the presence of blood proteins in the intestinal tract. AAT clearance is reliable for measuring protein loss distal to the pylorus. A serum sample is required to interpret results as a serum deficiency of AAT would make the AAT fecal excretion lower and could invalidate the test utility.
Gastrointestinal protein enteropathy has been associated with regional enteritis, sprue, Whipple intestinal lipodystrophy, gastric carcinoma, allergic gastroenteropathy, intestinal lymphangiectasia, constrictive pericarditis, congenital hypogammaglobulinemia, and iron deficiency anemia associated with intolerance to cow's milk. Increased fecal excretion of AAT can be found in small and large intestine disease and is applicable to adult and children.
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.
CLEARANCE:
< or =27 mL/24 h
FECAL ALPHA-1-ANTRYPSIN CONCENTRATION:
< or =54 mg/dL
SERUM ALPHA-1-ANTRYPSIN CONCENTRATION:
100-190 mg/dL
Interpretation
Provides information to assist in interpretation of the test results
Elevated alpha-1-antitrypsin (AAT) clearance suggests excessive gastrointestinal protein loss. The positive predictive value of the test has been found to be 97.7% and the negative predictive value is 75%.
Patients with protein-losing enteropathies generally have AAT clearance values greater than 50 mL/24 hours and AAT fecal concentrations above 100 mg/dL.
Borderline elevations above the normal range are equivocal for protein-losing enteropathies.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
In the absence of either a 24-hour fecal collection or a contemporary serum specimen, the fecal concentration of alpha-1-antitrypsin (AAT) can be used as a surrogate marker. The clearance test is preferred as it normalizes the large range of serum AAT concentrations and the variability in random fecal AAT concentrations.
When gastric loss of AAT is suspected (eg, Menetrier disease), AAT clearance is not a reliable indicator of protein loss as AAT is sensitive to pH less than3 and rapidly destroyed. When gastric protein loss is suspected and the AAT clearance is normal, the recommendation is to repeat testing after starting an acid suppressive medication regime.
Urine contamination from patients with kidney failure and increased total protein may adversely affect fecal AAT concentration. Suggest catheterizing patient prior to collection if clinically indicated.
Quantitation of specific proteins by nephelometric means may not be possible in lipemic sera due to the extreme light scattering properties of the specimen. Turbidity and particles in the specimen may result in extraneous light scattering signals, resulting in variable specimen analysis.
Supportive Data
Protein-losing enteropathy has been studied by intravenous injection of radioactive chromium chloride or labeled human serum albumin. The correlation between radiochromium and stool alpha-1-antitrypsin clearance has been measured with excellent correlation coefficients.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Florent C, L'Hirondel C, Desmazures C, Aymes C, Bernier JJ. Intestinal clearance of alpha 1-antitrypsin. A sensitive method for the detection of protein losing enteropathy. Gastroenterology. 1981;81(4):777-780
2. Crossley JR, Elliott RB. Simple method for diagnosing protein-losing enteropathies. Br Med J. 1977;1(6058):428-429
3. Perrault J, Markowitz H. Protein-losing gastroenteropathy and the intestinal clearance of serum alpha-1-antitrypsin. Mayo Clin Proc. 1984;59(4):278-279
4. Schmidt PN, Blirup-Jensen S, Svendsen PJ, Wandall JH. Characterization and quantification of plasma proteins excreted in faeces from healthy humans. Scand J Clin Lab Invest. 1995;55(1):35-45
5. Davidson NO: Intestinal lipid absorption. In: Yamada T, Alpers DH, Kaplowitz N, eds. Textbook of Gastroenterology. JB Lippincott; 2003:413
6. Rybolt AH, Bennett RG, Laughon BE, Thomas DR, Greenough WB 3rd, Bartlett JG: Protein-losing enteropathy associated with Clostridium difficile infection. Lancet. 1989;1(8651):1353-1355
7. Molina JF, Brown RF, Gedalia A, Espinoza LR. Protein losing enteropathy as the initial manifestation of childhood systemic lupus erythematosus. J Rheumatol. 1996;23(7):1269-1271
8. Umar SB, DiBaise JK. Protein-losing enteropathy: case illustrations and clinical review. Am J Gastroenterol. 2010;105(1):43-49
9. Levitt DG, Levitt MD. Protein losing enteropathy: comprehensive review of the mechanistic association with clinical and subclinical disease states. Clin Exp Gastroenterol. 2017;10:147-168
10. Murray FR, Morell B, Biedermann L, Schreiner P. Protein-losing enteropathy as precursor of inflammatory bowel disease: A review of the literature. BMJ Case Rep. 2021;14(1):e238802
Method Description
Describes how the test is performed and provides a method-specific reference
Immunonephelometry quantitates the alpha-1-antitrypsin (AAT) contained in a 24-hour fecal collection. From the concentration of feces and serum AAT, a 24-hour clearance is calculated. In the absence of a serum specimen or a timed fecal collection, an AAT fecal concentration will be reported.(Instruction manual: Siemens Nephelometer II Operations. Siemens, Inc; Version 2.4, 07/2019)
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 Friday
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 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.
CPT codes are provided by the performing laboratory.
82103 x 2
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 |
|---|---|---|
| A1AFS | Alpha-1-Antitrypsin Clearance | 93419-0 |
| 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.
|
|---|---|---|
| AAT24 | Alpha-1-Antitrypsin, 24 Hr, F | 9407-8 |
| CRCLR | Clearance | 18271-7 |
| AATS | Alpha-1-Antitrypsin, S | 6771-0 |