Serum antibodies anti-H. pylori and anti-CagA: A comparison between four different assays

The authors compare efficacy of two ELISA assays (one supplied by DIAMEDIX [Delta Biological s.r.l.], and the other by RADIM [RADIM I]) in detecting t otal anti-H, pylori antibodies, and of two further ELISA methods (one suppl ied by EUROSPITAL [Helori CTX IgG] and the other by RADIM [RADIM 2]) in ide ntifying anti-CagA antibodies, using sera from 69 controls (20 adults and 4 9 children) and from 96 patients, obtained before endoscopy. Seventy-three of the patients had H. pylori infection, while the remaining 23 were H. pyl ori negative (histology and polymerase chain reaction [PCR]). Fifty-two of the H. pylori positive patients, had cagA-positive strain infection, identi fied by PCR. The DIAMEDIX assay was found to be more sensitive (92%) than R ADIM 1 (79%) in identifying H. pylori positive patients, irrespective of th e infecting strain, On the other hand, the DIAMEDIX assay was less specific than RADIM 1 for H. pylori-negative patients (43% vs. 83%). However, when patients already treated for H. pylori infection were excluded from the gro up of H. pylori-negative patients, the DIAMEDIX assay had a specificity of 89%. In identifying anti-CagA antibodies, the kit supplied by RADIM (RADIM 2) had a sensitivity of 90% and a specificity of 94%, whereas that supplied by EUROSPITAL had a sensitivity of 100% and a specificity of 76%. The perf ormances of the two methods in the identification of anti-CagA antibodies w ere found to be similar. The authors conclude that, in view of its high sen sitivity, the DIAMEDIX assay may be useful in screening for H. pylori infec tion. J. Clin. Lab. Anal. 13:194-198, 1999. (C) 1999 Wiley-Liss, Inc.