Alpha-1-antitrypsin faeces

Specimen:

Random: 5 g faeces; a test for occult blood in faeces should also be performed to exclude bleeding as a cause of an elevated α-1 antitrypsin.

A clearance study requires a three day faecal collection (faeces should be frozen during collection period if possible) plus 5 mL blood in a plain tube for serum α1-antitrypsin assay.

Method:

Immunoassay.

Reference Interval:

Random: < 1.5 mg/g dry weight

Clearance: < 12.5 mL/day.

Application:

Investigation of protein-losing enteropathies.

Interpretation:

If α-1 antitrypsin is elevated in the absence of a positive occult blood test, increased loss of plasma proteins from the bowel is present. If occult blood is positive, the α1-antitrypsin is at least partly derived from blood loss, but a coexistent Protein-losing enteropathy cannot be excluded.

An approximate assessment of intestinal plasma protein loss can be made by estimating the clearance of α-1 antitrypsin from plasma into faeces (that is, the volume of plasma cleared of α-1 antitrypsin per day).

Reference:

Perlmutter DH. Gastroenterol Clin N Am 1995; 24: 27-43.