Recombinant human tissue transglutaminase for diagnosis and follow-up of childhood coeliac disease

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).

Immunochromatographic sticks for tissue transglutaminase and antigliadin antibody screening in celiac disease

BACKGROUND & AIMS

We investigated two 1-step immunochromatographic visual assays based on human recombinant tissue-transglutaminase (t-TG) as an alternative to enzyme-linked immunosorbent assays (ELISAs) for celiac disease (CD) screening.

METHODS

We used a tissue-transglutaminase (t-TG) stick, which detected immunoglobulin A/G (IgA/G) antibodies to t-TG, and a t-TG/antigliadin antibodies (AGA) stick, which detected IgA antibodies to both t-TG and AGA, as well as t-TG and AGA ELISAs, to determine t-TG and AGA antibodies in untreated celiac patients with subtotal villous atrophy. A total of 142 children (3 IgA-deficient sera) and 30 adults, and 140 controls (normal mucosa; 121 children and 19 adults), plus 23 sera from pediatric CD patients in remission were assayed.

RESULTS

For pediatric patients, with the t-TG stick we obtained a sensitivity of 97.1% and a specificity of 99.0%, and in adults, 83.3% and 100%, respectively. The t-TG/AGA stick displayed a sensitivity of 95.7% and a specificity of 99.0% for t-TG and a sensitivity of 89.2% and a specificity of 95.8% for AGA in children, and a sensitivity of 80% and a specificity of 100% for t-TG and a sensitivity of 83.3% and a specificity of 100% for AGA in adults. Results were comparable with the corresponding ELISAs.

CONCLUSIONS

The 2 visual assays are efficient for CD screening as an alternative to ELISAs. They are simple to handle and to interpret. By the combined use of the 2 sticks, IgA-deficient patients can be identified as positive in the t-TG (IgG/A) but negative in the t-TG/AGA (IgA) stick.

Recombinant autoantigens for diagnosis and therapy of autoimmune diseases

The characteristic of autoimmune diseases resides in the existence of T- and B-cell autoreactivity when directed against self-proteins. Thus autoantibodies are considered to be of diagnostic relevance. The advent of recombinant protein expression technology has made it possible to produce economically high-quality autoantigens for use in immunoassays for detecting autoantibodies in patients' sera. The intention of this short review is to give the reader a brief description of autoantigen production methodologies with their advantages, disadvantages and the limitations of these techniques in the diagnostics of autoimmune diseases. Further possible usage of recombinant autoantigens as tools in investigation and therapy of autoimmune diseases is discussed.

Fluctuating transglutaminase autoantibodies are related to histologic features of celiac disease

BACKGROUND & AIMS

Asymptomatic children at risk for celiac disease (CD) and seropositive for immunoglobulin A anti-TG autoantibodies (TGAA) may lack small intestinal mucosal changes characteristic of CD. We have followed a group of children with serial testing for TGAA.

METHODS

Subjects were a group of at-risk children comprised of infants expressing HLA-DR3 on newborn screening, those with type 1A diabetes, or a first-degree relative of someone with type 1 diabetes. All children participating in the prospective study for development of CD underwent serial testing for TGAA. Data from clinical evaluation and small intestinal biopsy were compared to the TGAA levels followed over time.

RESULTS

In 42 children, serial TGAA determinations while on a gluten-containing diet showed levels fluctuating 10-100-fold over 3-12 months. A TGAA index more than 0.5 had a positive predictive value (PPV) for histologic confirmation of CD of 96% (22/23). A TGAA index above the usual cutoff for positivity (0.05) had a PPV of only 76% (28/37).

CONCLUSIONS

In children with TGAA seropositivity, the TGAA level varied over time and a higher titer predicted an abnormal biopsy characteristic of CD. A threshold for biopsy for diagnosis of CD could be set higher for screening-identified cases than for clinically identified cases to decrease the frequency of performing "normal" biopsies.

Prevalence of Celiac disease among children in Finland

BACKGROUND

Wheat, rye, and barley proteins induce celiac disease, an autoimmune type of gastrointestinal disorder, in genetically susceptible persons. Because the disease may be underdiagnosed, we estimated the prevalence of the disease and tested the hypothesis that assays for serum autoantibodies can be used to detect untreated celiac disease and that positive findings correlate with specific HLA haplotypes.

METHODS

Serum samples were collected from 3654 students (age range, 7 to 16 years) in 1994 and screened in 2001 for endomysial and tissue transglutaminase antibodies. HLA typing was also performed on stored blood samples. All antibody-positive subjects were asked to undergo small-bowel biopsy in 2001.

RESULTS

Of the 3654 subjects, 56 (1.5 percent) had positive antibody tests, as determined in 2001. Results of the two antibody tests were highly concordant. As of 1994, none of the subjects had received a clinical diagnosis of celiac disease, but 10 who had positive tests for both antibodies in serum obtained in 1994 received the diagnosis between 1994 and 2001. Of the 36 other subjects with positive antibody assays who agreed to undergo biopsy in 2001, 27 had evidence of celiac disease on biopsy. Thus, the estimated biopsy-proved prevalence was 1 case in 99 children. All but two of the antibody-positive subjects had either the HLA-DQ2 or the HLA-DQ8 haplotype. The prevalence of the combination of antibody positivity and an HLA haplotype associated with celiac disease was 1 in 67.

CONCLUSIONS

The presence of serum tissue transglutaminase and endomysial autoantibodies is predictive of small-bowel abnormalities indicative of celiac disease. There is a good correlation between autoantibody positivity and specific HLA haplotypes. We estimate that the prevalence of celiac disease among Finnish schoolchildren is at least 1 case in 99 children.