Sixteen studies (n=6,085) were included in the review: 13 cohort (three of which were retrospective) and three nested case-control studies. Sample sizes ranged from 79 to 2,000 patients. Four studies performed well on quality and scored a positive assessment on at least eight of 11 items. The other studies suffered either from some form of bias or (in many cases) items could not be scored due to insufficient information.
Performance of individual abdominal symptoms varied among studies and it was not possible to pool the results. Diarrhoea had a sensitivity of 0.27 to 0.86 and specificity of 0.21 to 0.86 (six studies). Results for other abdominal symptoms were reported in the review with likelihood ratios close to one, which indicated poor performance.
Studies that assessed the diagnostic value of immunoglobulin A or G antigliadin antibodies (IgA-AGA or IgG-AGA) also reported variation and results could not be pooled. Sensitivity ranged between 0.46 and 0.87 for IgA-AGA (six studies) and between 0.25 and 0.93 for IgG-AGA (five studies) and specificity ranged between 0.70 and 0.98 for IgA-AGA and between 0.80 and 0.99 for IgG-AGA.
IgA anti-endomysial antibodies (EmA) showed pooled sensitivity of 0.90 (95% CI 0.80 to 0.95; eight studies) and specificity of 0.99 (95% CI 0.98 to 1.00; eight studies). Pooled estimates for IgA anti-tissue transglutaminase antibodies (IgA-tTG) (seven studies) showed sensitivity of 0.89 (95% CI 0.82 to 0.94) and specificity of 0.98 (95% CI 0.95 to 0.99).
Results from studies that assessed use of IgG-tTG and/or deamidated gliadin peptides (IgA-DGP) were reported in the review.
Subgroup analyses and sensitivity analyses were reported in the review.