Screening for coeliac disease using anti-tissue transglutaminase antibody assays, and prevalence of the disease in an Australian community.
OBJECTIVE
To determine (i) the prevalence of positive results of anti-tissue transglutaminase (anti-tTG) antibody assays and coeliac disease (CD) in a rural Australian community; and (ii) whether confirmatory testing of a positive assay result with an alternative anti-tTG assay improved the positive predictive value of the test in population screening for CD.


METHODS
Retrospective analysis in December 2004 of stored serum samples taken in 1994-1995 from 3011 subjects in the Busselton Health Study follow-up. Assays for IgA and IgG anti-tTG antibodies were performed, and positive or equivocal samples were retested with a different commercial anti-tTG assay. Available subjects with one or more positive assay results were interviewed, had serum collected for repeat anti-tTG assays and for HLA-DQ2 and HLA-DQ8 haplotyping and, if appropriate, gastroscopy and duodenal biopsy were performed. In unavailable subjects, HLA-DQ2 and -DQ8 haplotyping was performed on stored sera. Total serum IgA levels were assessed in subjects with initially negative assay results.


METHODS
Prevalence of anti-tTG positivity and biopsy-proven CD.


RESULTS
In 47 of 3011 serum samples (1.56%), at least one anti-tTG assay gave positive results: 31 of the subjects who provided these sera were available for clinical review, and 21 were able to have a gastroscopy. Seventeen subjects (0.56%) were diagnosed with definite CD (14 were confirmed at gastroscopy, and three unavailable subjects had three positive results of anti-tTG assays and an HLA haplotype consistent with CD); in a further 12 unavailable subjects, CD status was considered equivocal, with one or more positive anti-tTG assay results and an HLA haplotype consistent with CD. If these subjects were regarded as having CD, the prevalence of CD would be 0.96%. The positive predictive value when all three anti-tTG assays gave positive results was 94%, but fell to 45.2% with only one positive result.


CONCLUSIONS
The prevalence of anti-tTG antibodies in this population is 1.56%; the prevalence of CD is at least 0.56%. The utility of a single, positive result of an anti-tTG assay in screening for CD in the community is poor, and repeat and/or collateral assessment with different assays may decrease the need for gastroscopy and distal duodenal biopsy.
Chin
Marcus W
MW
Department of Hepatology, Sir Charles Gairdner Hospital, Perth, WA. marcus.chin@health.wa.gov.au
Mallon
Dominic F
DF
Cullen
Digby J
DJ
Olynyk
John K
JK
Mollison
Lindsay C
LC
Pearce
Callum B
CB
D000328:Adult; D000368:Aged; D001315:Australia; D002446:Celiac Disease / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood*; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012423:Rural Health; D011503:Transglutaminases / Q000276:immunology*; D055815:Young Adult
D007070:Immunoglobulin A; D007074:Immunoglobulin G; D011503:Transglutaminases