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Measurement of faecal α 1 ‐antitrypsin: Methodologies and clinical application
Author(s) -
CHOUDHARY SITARAM,
GIBSON PETER R,
DEACON MELISSA C,
YOUNG GRAEME P
Publication year - 1996
Publication title -
journal of gastroenterology and hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.214
H-Index - 130
eISSN - 1440-1746
pISSN - 0815-9319
DOI - 10.1111/j.1440-1746.1996.tb01377.x
Subject(s) - medicine , medical physics
Abstract Presence of the serum protein, α 1 ‐antitrypsin, in the faeces is a potentially useful marker for gastrointestinal disease and/or blood loss. In an effort to simplify faecal sampling procedures, we evaluated the performance of measuring α 1 ‐antitrypsin in eluants of thin smears of faeces made on filter paper, relative to conventional measurement in aqueous extracts of stool. Faecal specimens and smears were collected from healthy subjects ( n = 22) and from patients with gastrointestinal bleeding ( n = 12) or inflammation ( n = 22), colorectal neoplasia ( n = 15), or miscellaneous diseases with a low risk of excessive faecal protein loss ( n = 30). α 1 ‐Antitrypsin was measured by ELISA and haem porphyrins (as a measure of blood loss) by HemoQuant tm . Results from smears were highly correlated (r = 0.81; P < 0.001) with faecal α 1 ‐antitrypsin. The smear method detected an elevated faecal α 1 ‐antitrypsin with 93% specificity and 75% sensitivity. Sensitivity was high (> 88%) where levels were markedly elevated in inflammatory and bleeding groups and low (< 62%) where abnormal levels were mildly elevated (neoplasia and miscellaneous groups). Elevated α 1 ‐antitrypsin detection by either method positively predicted > 90% of patients with gastrointestinal inflammatory disease when levels were elevated 6‐fold and 1.5‐fold or more, respectively. In 15 patients with colorectal neoplasia, faecal α 1 ‐antitrypsin was elevated in 10 patients, haem porphyrins in nine patients and either in 12; however, smear eluant levels were elevated in only six patients. Blood loss was probably a major contributor to elevated faecal α 1 ‐antitrypsin in some patients but not in the inflammatory group as a whole. The sampling and aesthetic advantages of the smear eluant method are offset by reduced sensitivity, precluding its use as a screening test for colorectal neoplasia. However, its performance in predicting inflammatory disease is equivalent to that of conventional measurement and warrants a prospective evaluation as an early investigative test. Concurrent evaluation of blood loss may improve its interpretation.