Alpha-1-Antitrypsin, Random Feces

Message

Performed at SJC

Test code 14628X;535118

Test Code

AATSTR

Quest Code

14628X

Alias/See Also

14628

CPT Codes
82103

Preferred Specimen

10 g stool collected in a plastic, sterile leakproof container

Minimum Volume

2 g

Instructions

Collect fresh stool in a plastic, leakproof container.
Adult and older children patients can collect the specimen by passing feces into plastic wrap stretched loosely over the toilet bowl. Then transfer 10g of the stool specimen into the plastic container.
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 10g of the stool specimen from the plastic-lined diaper to the plastic container. Do not submit the diaper itself.
Freeze and transport frozen.

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: Indefinitely
Frozen: Indefinitely

Methodology
Nephelometry

Setup Schedule

Set up: Mon-Fri; Report available: 2-3 days

Report Available

1-7 Days

Reference Range

<55 mg/dL

Clinical Significance

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.

Performing Laboratory
Quest Diagnostics Chantilly Nichols Institute
14225 Newbrook Dr.
Chantilly, VA 20151-2228

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.