ALPHA-1-ANTITRYPSIN - faeces

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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 a1-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 a1-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 a1-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 a1-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 a1-antitrypsin from plasma into faeces (ie the volume of plasma cleared of a1-antitrypsin per day).

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

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