A novel visual immunoassay for coeliac disease screening

Background To date, the most commonly accepted techniques for the screening of coeliac disease are indirect immunofluorescence and enzyme‐linked immunosorbent assay (ELISA), which reveal antiendomysium and antigliadin antibodies respectively. We report the use of a simple visual system for coeliac disease screening based on the use of Staphylococcus aureus protein A, which binds to both IgG and IgA, thus avoiding the need for two parallel immunoassays. Materials and methods Opaque polystyrene microwell strips coated with a wheat gliadin extract were incubated with sera followed by incubation with protein A–colloidal gold conjugate. The resulting colour was compared with that of positive and negative control sera. The procedure took less than an hour. Results One hundred and forty‐five biopsy‐proven sera, 94 from active coeliac patients and 51 from non‐coeliac patients with diverse gastrointestinal pathologies or diabetes mellitus, were assayed. Ninety of the 94 sera from the active coeliac patients were positive, whereas only 3 of the 51 non‐coeliac control subjects were positive. The technique has a sensitivity of 95.7% and a specificity of 94.1%. Conclusions The sensitivity and specificity of the visual system are greater than those of most ELISA systems and are similar to those observed with IgA antiendomysium antibodies when tested in the same population. Moreover, it is inexpensive, quick, simple to perform and easy to interpret, i.e. it requires no qualified personnel. It is for these features, together with the outstanding sensitivity and specificity, that we propose this immunoassay as a new test for reliable coeliac disease screening.