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| 80450:ALPHA-1-ANTITRYPSIN CLEARANCE, STOOL AND SERUM | |||||||||
| Alias Names: | Antitryp Bl/St / A1 Antitryp Clear / A1 ClearAn / A1A / a-1-Antitrypsin, F&S / AIA F&S / Soft-CA1A | ||||||||
| Methodology: | Nephelometry | ||||||||
| Edit Date: | 8/16/2010 | ||||||||
| Components: | Clearance / Alpha-1-Antitrypsin, Fecal | ||||||||
| Performed: | Monday-Saturday | ||||||||
| Released: | 2 hours after setup at PeaceHealth Laboratories’ reference lab. | ||||||||
| Specimen Collection Details | |||||||||
| Collection: | 24-hour stool specimen in pre-weighed Mayo stool containers, AND one 7.5 mL serum separator tube (SST). Blood must be collected during the stool collection period. Both serum and entire stool collection are required. | ||||||||
| Handling: | Allow to clot, centrifuge and separate serum into a plastic vial. Freeze serum and freeze stool collection. | ||||||||
| Standard Volume: | 1 mL serum and entire stool collection. | ||||||||
| Minimum Volume: | 1 mL serum and entire stool collection. | ||||||||
| Transport: | Frozen on dry ice. | ||||||||
| Comments: | Useful for diagnosing protein-losing enteropathies. Alpha-1-antitrypsin (A1A) 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. A1A clearance is reliable for measuring protein loss distal to the pylorus. |
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| Rejection Criteria: | Random stool specimen. | ||||||||
| Reference Range: | |||||||||||||||||||
| Clearance | ≤ 27 mL/24 hours | ||||||||||||||||||
| Fecal alpha-1-antitrypsin concentration | ≤ 54 mg/dL | ||||||||||||||||||
| Serum alpha-1-antitrypsin concentration | 100-190 mg/dL | ||||||||||||||||||
| Elevated A1A 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 A1A clearance values >50 mL/24 hours and A1A stool concentrations >100 mg/mL. Borderline elevations above the normal range are equivocal for protein-losing enteropathies. |
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