Specimens:
(1) serum alpha-1 antitrypsin in mg/dL
(2) 24 hour stool collection in grams or mL
fecal alpha-1 antitrypsin excretion in mg/24 hours =
= (fecal alpha-1 antitrypsin concentration in mg/dL) * ((24 hours stool volume in mL) / 100)
alpha-1 antitrypsin clearance in mL per 24 hours =
= (fecal alpha-1 antitrypsin excretion in mg/24 hours) / ((serum alpha-1 antitrypsin in mg/dL) / 100)
where:
• The division by 100 in the first equation is to convert mL to dL.
• The division by 100 in the second equation is to convert mg/dL to mg/mL.
Alternatively the 24 hours stool can be measured as grams dry fecal weight per 24 hours and the fecal alpha-1 antitrypsin given in mg per 100 grams dry fecal weight).
fecal alpha-1 antitrypsin in mg/24 hours =
= (fecal alpha-1 antitrypsin in mg/100 g dry stool) * (24 hour dry fecal weight in g) / 100
Interpretation:
• Bai et al report that the upper limit of the normal reference range for clearance is 16 mL per 24 hours
• Perednia and Curosh report that the upper limit of the normal reference range for clearance is < 13 mL per 24 hours.
• The change in the clearance can be used to monitor severity of the enteropathy. The clearance should decrease with disease remission.
