Qualitative differences in faecal alpha-1-antitrypsin in patients with Crohn's disease.

Correspondence Qualitative differences in faecal alpha-1-antitrypsin in patients with Crohn's disease SIR,-The use of faecal alpha-1-antitrypsin (A-1-AT) in the assessment of Crohn's disease (CD) activity remains controversial. In a recent study Fischbach et al found no correlation of faecal A-1-AT with ESR, serum albumin, orosomucoid, activity index of Van Hees, or CDAI.' Conversely, faecal A-1-AT was well correlated with a clinical score, serum oroso-mucoid, and C-reactive protein in another work by Meyers et al.2 We think that biochemical changes of A-1-AT in the intestine, resulting in an apparent decrease of its faecal concentration, when measured by standard radial immunodiffusion, could explain these discrepancies. We have compared3 the biochemical characteristics of faecal A-1-AT in 14 CD (five men, nine women, mean age 28 years) and in 10 healthy controls (six men, four women, mean age 30 years). The CD location was the ileum in five of 14, the ileum and colon in seven of 14, and the colon in two of 14; the mean duration of disease was 4-8 years (0-2-20). According to CDAI, the disease was active in II of 14 patients and inactive in three of 14. Twenty four hour stools were collected for three days and homogenised. After preparation, sodium dodecylsulphate poly-acrylamide gel electrophoresis and immunoblot were applied to analysis of faecal A-i-AT. Two main A-1-AT biochemical forms of respectively 38 000 molecular weight and 51000 mol wt were characterised. Faecal extracts from controls contained only the 38000 mol wt A-1-AT component. Both 38 000 and 51 000 mol wt A-1-AT were found in faeces of patients with CD. Fifty-one thousand mol wt A-1-AT was only recovered in patients with active CD (eight of 11), while 38000 mol wt alpha-I-AT was present in three of 11 patients with active CD and three of three with inactive CD. No relationship was established between the form of faecal A-I-AT and sex or age of the patients as well as duration of CD or its location. Thus different forms of A-1-AT exist in the faeces of patients with CD. This could account for the controversial performances of faecal A-1-AT as a marker of CD activity: when measured by standard radioimmunodiffusion in some faecal samples, concentration of 38000 mol wt A-1-AT was underestimated by almost 20% as compared with native 54 000 mol wt A-1-AT. Further isolation of different A-1-AT in faeces (especially 51000 mol wt form) might lead to determination of …