|Values are valid only on day of printing.|
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.
Gastrointestinal protein enteropathy has been associated with regional enteritis, sprue, Whipple intestinal lipodystrophy, gastric carcinoma, allergic gastroenteropathy, intestinal lymphangiectasia, constrictive pericarditis, congenital hypogammaglobulinemia, and iron deficiency anemia associated with intolerance to cow's milk.
Diagnosing protein-losing enteropathies
Elevated alpha-1-antitrypsin (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.
In the absence of either a 24-hour stool collection or a contemporary serum specimen, the fecal concentration of alpha-1-antitrypsin (A1A) can be used as a surrogate marker. The clearance is preferred in order to normalize the large range of serum A1A concentrations and the variability in random stool A1A concentration.
Clearance: < or =27 mL/24 hours
Fecal alpha-1-antitrypsin concentration: < or =54 mg/dL
Serum alpha-1-antitrypsin concentration: 100-190 mg/dL
1. Florent C, L'Hirondel C, Desmazures C, et al: Intestinal Clearance of alpha 1-antitrypsin. A sensitive method for the detection of protein losing enteropathy. Gastroenterology 1981;81:777-780
2. Crossley JR, Elliott RB: Simple method for diagnosing protein-losing enteropathy. Br Med J 1977;1:428-429
3. Perrault J, Markowitz H: Protein-losing gastroenteropathy and the intestinal clearance of serum alpha-1-antitrypsin. Mayo Clin Proc 1984;59:278-279