Anti-human versus anti-guinea pig tissue transglutaminase antibodies as the first-level serological screening test for coeliac disease in the general population.

BACKGROUND: So far the reliability of the anti-guinea pig and anti-human tissue transglutaminase antibodies for the coeliac disease diagnosis has been evaluated in selected groups of patients. AIM: To compare the diagnostic accuracy of anti-human versus anti-guinea pig tissue transglutaminase in the coeliac disease screening of the general population. SUBJECTS: Two healthy Italian populations living in Marche region and in Western Sardinia. METHODS: Both anti-guinea pig and anti-human tissue transglutaminase were determined using an enzyme-linked immunosorbent assay-based commercially available kit (Eu-tTG, Eurospital, Trieste, Italy). RESULTS: During the period 1999-2001, 3541 subjects (1500 from "continental" Italy and 2041 from Sardinia) were screened for coeliac disease using both anti-guinea pig and anti-human tissue transglutaminase as first-level tests. Both these tests were negative in 3439/3541 sera, while 29 resulted positive for both of them and 73 showed discordant results. Overall, 50 intestinal biopsies were performed in 22, 21 and 7 subjects with positivity to both screening tests, to anti-guinea pig and to anti-human tissue transglutaminase alone, respectively. A coeliac disease diagnosis was made in 25 subjects giving an overall prevalence of 1:126 individuals. The anti-tissue transglutaminase specificity and sensitivity were 98 and 92% for guinea pig and 99.6 and 96% for human tissue transglutaminase, respectively. CONCLUSIONS: The anti-human tissue transglutaminase test should definitely replace the anti-guinea pig-derived one as first-level screening tool for identifying all subjects who need the second-level investigations (small intestinal biopsy).

Antiendomysium versus antigliadin antibodies in screening the general population for coeliac disease.

BACKGROUND: It has recently been shown that mass screening for coeliac disease, using either the serum antigliadin (AGA) or antiendomysium antibodies (EMA) as screening test, can detect large numbers of cases that had escaped clinical diagnosis. The influence of the diagnostic algorithm on the results of the coeliac screening has not yet been evaluated. Our aim was to compare the validity of the AGA and the EMA protocols in 2096 students living in northwest Sardinia, who took part in a serologic screening for coeliac disease. METHODS: The sample included 2096 of 2345 eligible students (89%) aged 11-15 years who underwent serum IgG AGA, IgA AGA, and IgA EMA determinations. Total serum IgA level was measured in sera showing isolated IgG AGA positivity. Subjects showing at least one of the following: a) EMA positivity, b) IgA AGA positivity, or c) IgG AGA positivity and IgA deficiency (<5 mg/dl) were asked to submit to a small-intestinal biopsy. RESULTS: The prevalence of coeliac disease was 19 (16 showing typical enteropathy, 1 potential case, and 2 known cases) of 2096 (0.91%; 95% confidence interval = 0.50-1.31). Seventeen small-intestinal biopsy specimens were needed to confirm 16 cases of manifest coeliac disease (positive predictive value (PPV) = 94%) by the EMA protocol, whereas the AGA protocol required 21 biopsy specimens for 12 cases of coeliac disease (PPV = 57%). None of six IgA-deficient, IgG AGA-positive cases detected by the AGA protocol also had coeliac disease. CONCLUSIONS: The EMA protocol is superior to the AGA protocol for mass screening of coeliac disease because of higher sensitivity, decreased need for intestinal biopsy, and possibility to detect potential cases of coeliac disease.