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HelpTest ID: A1AFS Alpha-1-Antitrypsin Clearance, Feces and 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.
Specimen Required
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.
Useful For
Diagnosing protein-losing enteropathies
Profile Information
| 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
Nephelometry
Reporting Name
Alpha-1-Antitrypsin ClearanceSpecimen Type
FecalSerum
Specimen Minimum Volume
Homogenized feces: 1 mL; Serum: 0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Fecal | Frozen (preferred) | 14 days |
| Ambient | 14 days | |
| Refrigerated | 14 days | |
| Serum | Frozen (preferred) | 28 days |
| Ambient | 28 days | |
| Refrigerated | 28 days |
Clinical Information
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
CLEARANCE:
≤27 mL/24 h
FECAL ALPHA-1-ANTRYPSIN CONCENTRATION:
≤54 mg/dL
SERUM ALPHA-1-ANTRYPSIN CONCENTRATION:
100-190 mg/dL
Interpretation
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.
Clinical Reference
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
Day(s) Performed
Monday through Friday
Report Available
1 to 3 daysTest Classification
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
82103 x 2
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| A1AFS | Alpha-1-Antitrypsin Clearance | 93419-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| AAT24 | Alpha-1-Antitrypsin, 24 Hr, F | 9407-8 |
| AATS | Alpha-1-Antitrypsin, S | 6771-0 |
| CRCLR | Clearance | 18271-7 |
Forms
If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Test Request (T728) with the specimen.
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