Fecal alpha-1 protease inhibitor testing is used for what purpose?

• A. To detect renal protein loss
• B. To assess intestinal pH
• C. To measure pancreatic enzyme activity
• D. To detect intestinal protein loss

Answer: (D)

Fecal alpha-1 protease inhibitor testing is used to detect intestinal protein loss, i.e., protein-losing enteropathy. The test relies on alpha-1 antitrypsin, a protease inhibitor that resists degradation in the gut; when proteins leak into the GI lumen, this inhibitor shows up in the stool. A positive result points to intestinal loss of protein as the cause of hypoalbuminemia, helping distinguish it from renal protein loss (which would not raise stool levels) and from issues like pancreatic enzyme activity or intestinal pH, which don’t reflect mucosal protein leakage. In short, this test specifically indicates that proteins are being lost through the intestines rather than through the kidneys.