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Alpha-1-Antitrypsin, Feces, 24-Hour
Message**Take to processing, specimen needs to be frozen ASAP.
Total weight needs to be documented and specimen aliquoted for send out.
Total weight needs to be documented and specimen aliquoted for send out.
Test Code
30523
Alias/See Also
LAB558
CPT Codes
82103
Preferred Specimen
10 grams of a 24-hour stool
Minimum Volume
2 grams
Instructions
Freeze feces specimens -20° C and send frozen samples on dry ice
Transport Container
Transport tube
Transport Temperature
Frozen
Specimen Stability
Room temperature: Unacceptable
Refrigerated: 8 days
Frozen: 28 days
Refrigerated: 8 days
Frozen: 28 days
Methodology
Nephelometry
Setup Schedule
Sun-Fri
Report Available
3-4 days
Reference Range
<55 mg/dL
Clinical Significance
This test measures alpha-1-antitrypsin (AAT) concentration in a 24-hour stool specimen. The result of this test, preferably interpreted jointly with the result of a simultaneous plasma AAT level, may aid in the diagnosis of protein-losing enteropathy [1].
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 [2]. Measurement of radioactive albumin is the "gold standard" for gastrointestinal protein loss but is rarely performed because of the high cost and complex methodology [3]. 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 [1,2].
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 [2]. Abnormal results in patients with intestinal blood loss need to be interpreted carefully owing to the possibly increased AAT clearance [3]. AAT clearance, calculated from AAT concentrations in a 24-hour fecal specimen and a serum specimen, is more reliable for estimating protein loss [4].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Florent C, et al. Gastroenterology. 1981;81(4):777-780.
2. 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.
3. Strygler B, et al. Gastroenterology. 1990;99(5):1380-1387.
4. Levitt DG, et al. Clin Exp Gastroenterol. 2017;10:147-168.
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 [2]. Measurement of radioactive albumin is the "gold standard" for gastrointestinal protein loss but is rarely performed because of the high cost and complex methodology [3]. 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 [1,2].
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 [2]. Abnormal results in patients with intestinal blood loss need to be interpreted carefully owing to the possibly increased AAT clearance [3]. AAT clearance, calculated from AAT concentrations in a 24-hour fecal specimen and a serum specimen, is more reliable for estimating protein loss [4].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Florent C, et al. Gastroenterology. 1981;81(4):777-780.
2. 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.
3. Strygler B, et al. Gastroenterology. 1990;99(5):1380-1387.
4. Levitt DG, et al. Clin Exp Gastroenterol. 2017;10:147-168.
Performing Laboratory
Quest Diagnostics Nichols Institute-Chantilly VA |
14225 Newbrook Drive |
Chantilly, VA 20151-2228 |