Quantification of fecal alpha 1-antitrypsin excretion for assessment of inflammatory bowel diseases

Determination of fecal excretion of the serum proteinase inhibitor alpha(1)-antitrypsin (AAT) is established for quantification of intestinal protein loss. It was demonstrated to be increased both in quiescent and in active inflammatory bowel diseases (IBD, Crohn's disease and ulcerative colitis). The (patho)physiological rationale for measuring fecal AAT excretion and its role in the diagnostic and prognostic assessment of these disorders will be critically reviewed. Experimental and clinical data were selected from computerized MEDLINE literature search, manual review of bibliographies, and personal experiences of the authors. In IBD patients, fecal AAT excretion corresponds to gross assessment of clinical disease activity, endoscopic degree of intestinal inflammation, and any response to treatment. It appears to be an early indicator of subclinical bowel disease and its imminent exacerbation. However, there is neither strict correlation to summarizing clinical disease activity indices, nor to extent or location of intestinal inflammation. Fecal AAT excretion was also found to be elevated in active pouchitis, and to correlate to its severity. In summary, estimation of fecal AAT excretion is a sensitive, but non-specific parameter reflecting enteric inflammation in IBD individuals. It proved to be an independent supplementary variable for monitoring their intestinal disease activity, with some predictive value for their forthcoming clinical course.