Reassessment of faecal α-1-antitrypsin excretion for use as screening test for intestinal protein loss

Faecal α-1-antitrypsin and ⁵¹Cr-albumin losses in 42 patients with either gastrointestinal or hepatic disease were compared. The reference range was derived from measurements in 20 controls without gastrointestinal disease. Alpha-1-antitrypsin excretion was increased in patients with excessive ⁵¹Cr-albumin loss, and correlations were found between α-1-antitrypsin clearance and ⁵¹Cr-albumin excretion. Because of the considerable overlap of faecal α-1-antitrypsin excretion between controls and patients, sensitivity and specificity of the test were only 58% and 80%, respectively. This poor reliability could not be explained by sampling error or temporal variations in α-1-antitrypsin excretion. These results show that although faecal α-1-antitrypsin excretion correlates with ⁵¹Cr-albumin excretion when whole groups of patients are studied, its poor sensitivity makes it an unreliable measure of enteric protein loss.