Alpha-1 Antitrypsin, Feces
Code:6008
| Includes | Alpha-1 antitrypsin |
|---|
Analysis details
Methodology
- Enzyme-linked immunosorbent assay (ELISA)
Expected Turnaround Time
3 days
Special Instructions
- Do not use laxatives, rectal suppositories, or oils for 72 hours before collecting the stool specimen.
- With clinician approval, hold medications that affect intestinal motility (e.g., belladonna, pilocarpine) for 72 hours before collection.
- Avoid substances that discolor stool—such as iron, bismuth, or barium sulfate—for 72 hours prior to collection.
How to use
The Alpha-1 antitrypsin, feces test (fecal A1AT; stool alpha-1 antitrypsin) assists in assessing suspected protein-losing enteropathy by quantifying A1AT in stool. It also informs the evaluation of unexplained hypoalbuminemia and edema and may be included in the workup of chronic diarrhea and malabsorption. When a timed stool collection is paired with a concurrent serum A1AT measurement, the data may be used to compute alpha-1 antitrypsin clearance as an index of enteric protein loss.
Limitations
Alpha-1 antitrypsin (A1AT) is synthesized in the liver and functions as a serine protease inhibitor. Because it is relatively resistant to degradation by pancreatic and intestinal proteases, increased amounts recovered in stool reflect transudation of plasma proteins across the gastrointestinal mucosa. Measured fecal A1AT supports the diagnosis of protein-losing enteropathy and tracks with the magnitude of enteric protein loss; values <250 mg/L are generally negative, 250–500 mg/L are borderline, and >500 mg/L are positive. This fecal assay does not assess genetic A1AT deficiency. Evaluation of hereditary deficiency requires serum A1AT concentration with phenotype analysis or SERPINA1 genotyping.
| Unit | mg/L |
|---|---|
| Reference interval | — |
| Indications | Persistent or recurrent diarrhea, Unexplained or recurrent abdominal pain, Low total serum protein (hypoproteinemia), Reduced serum albumin (hypoalbuminemia), Peripheral or generalized edema, Anemia of unclear cause, States of vitamin deficiency, Involuntary weight loss |
Specimen Requirements
| Specimen | Stool |
|---|---|
| Container | Sterile Stool Container |
| Storage Instructions | Refrigerated, Frozen |