Quantitative antigliadin antibody measurement in clinical practice: an Italian multicentre study

Background. The determination of class G and A serum antigliadin antibodies remains one of the most widely used screening tests for coeliac disease. T he results from different laboratories are not always comparable, on accoun t of changes in the technique and the different ways of expressing the resu lts. Aims, To: a) evaluate the physiological variation of serum antigliadin anti bodies expressed in ng/ml, and b) establish the cut-off of quantitative ant igliadin antibodies. Patients, Patients were 127 individuals with active coeliac disease. Contro ls were 395 non-coeliac subjects (198 females and 197 males) aged 6 months to 45 years (median age: 4.9 years). Methods. Antigliadin antibody enriched samples were obtained by affinity ch romatography. The concentration of the eluted antigliadin antibodies was ev aluated by nephelometry and enzyme-linked immunosorbent assay to establish a primary standard. An enzyme-linked immunosorbent assay for antigliadin an tibody determination,vas run according to standard procedures. Results. lit controls, IgG-antigliadin antibody showed high variability in the 50th-90th centile range that peaked during the second year of life whil e IgA-antigliadin antibodies showed a lower variability and a less pronounc ed trend to decreasing values with age, A certain degree of overlapping bet ween controls and coeliac patients was seen for both IgA- and IgG-antigliad in antibodies. The receiver operating characteristic analysis skewed that t he best discrimination was achieved by a cut-off 8-10 ng/ml for IgA-antigli adin antibodies and 150-200 ng/ml for IgG-antigliadin antibodies. Conclusions, Antigliadin antibody concentration is not normally distributed and changes with age in non-coeliac subjects. The receiver operating chara cteristic analysis is a valuable tool for fixing the antigliadin antibody c ut-offs between control and diseased individuals. The diagnosis of coeliac disease should always be confirmed by intestinal biopsy.