Alpha-1-Antitrypsin, Random Feces
Test Summary
This test measures alpha-1-antitrypsin (AAT) concentration in a random stool specimen and may help screen for protein-losing enteropathy [1]. An AAT level measured in a 24-hour stool specimen and interpreted jointly with a simultaneous blood AAT level is generally preferred for the diagnosis of protein-losing enteropathy [2].
Protein-losing enteropathy is a disorder caused by inflammation or destruction of intestinal mucosa and subsequent increased loss of plasma protein through the gastrointestinal tract. Conditions associated with protein-losing enteropathy include but are not limited to inflammatory bowel disease, lymphoma, Whipple disease, systemic lupus erythematosus, and food allergies [3]. Measurement of radioactive albumin is the "gold standard" for gastrointestinal protein loss but is rarely performed because of the high cost and complex methodology [4]. AAT has a molecular weight similar to that of albumin and is resistant to proteolysis. Therefore, the excretion of AAT in stool can be used to estimate protein loss in the gastrointestinal tract [2,3].
Low stool AAT levels may also be caused by AAT deficiency or impaired hepatic synthesis of AAT; thus, they must be interpreted in conjunction with plasma AAT levels [3]. Abnormal results in patients with intestinal blood loss need to be interpreted carefully owing to the possibly increased AAT clearance [4].
An AAT level measured in a random stool specimen may not accurately reflect daily AAT excretion [2]. AAT clearance, calculated from AAT concentrations in a 24-hour fecal specimen and a serum specimen, is more reliable for estimating protein loss [5].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Thomas DW, et al. Gastroenterology. 1981;80(4):776-782.
2. Florent C, et al. Gastroenterology. 1981;81(4):777-780.
3. Sherwood RA, et al. Gastric, intestinal, and pancreatic function. In: Rifai R, et al, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier Inc; 2022.
4. Strygler B, et al. Gastroenterology. 1990;99(5):1380-1387.
5. Levitt DG, et al. Clin Exp Gastroenterol. 2017;10:147-168.
Aliases
- N/A
Specimen Collection
Special Instructions
Preferred Specimen
Minimum Volume
Instructions
With young children and infants wearing diapers, the diaper should be lined with clean plastic wrap to prevent absorption. A pediatric urine bag can be attached to the child to ensure that the stool specimen is not contaminated with urine. Then transfer 10 g of the stool specimen from the plastic lined diaper to the plastic container. Do not submit the diaper itself. Freeze and ship frozen.
Patient Preparation
Storage
Transport Temperature
Specimen Stability
- Room temperature: Unacceptable
- Refrigerated: Indefinitely
- Frozen: Indefinitely
Limitations
Other Acceptable Specimens
Unacceptable Specimens
Order Code
EPIC (Premier) Code
Includes
CPT Code
- 82103
Billing Code
- 700000
CPT Statement
Methodology
FDA Status
Physician Attestation of Informed Consent
Testing Laboratory
14225 Newbrook Drive
Chantilly VA, 20153
Reference Range
Setup Schedule / Expected Turnaround Time
Specimen Collection
Special Instructions
Preferred Specimen
Minimum Volume
Instructions
With young children and infants wearing diapers, the diaper should be lined with clean plastic wrap to prevent absorption. A pediatric urine bag can be attached to the child to ensure that the stool specimen is not contaminated with urine. Then transfer 10 g of the stool specimen from the plastic lined diaper to the plastic container. Do not submit the diaper itself. Freeze and ship frozen.
Patient Preparation
Storage
Transport Temperature
Specimen Stability
- Room temperature: Unacceptable
- Refrigerated: Indefinitely
- Frozen: Indefinitely