EVALUATION OF SEROLOGICAL ASSAYS FOR H PYLORI, CagA AND VacA ANTIBODIES IN PEDIATRIC PATIENTS WITH ABDOMINAL PAIN.

11 Helicobacter pylori (HP) is the principal etiologic agent responsible for peptic ulcer disease and chronic active gastritis. While in adults an accurate diagnosis can be obtained by endoscopic examination and biopsy of the gastric mucosa, endoscopy in children can be invasive and expensive. Serological tests for HP antibody are a diagnostic option for screening. Recently developed serologic assays also allow determination of antibodies to CagA and VacA proteins which are felt to be indicative of virulence. The purpose of the present investigation was to determine the accuracy of several serological assays in the diagnosis of HP gastritis in pediatric patients with abdominal pain, and to determine the prevalence of CagA and VacA in this patient population. Twenty-one pediatric patients (15 males, 6 females, mean age 11.2 years, range 2-16 years) underwent endoscopy and biopsy of the gastric mucosa. The presence of HP in the biopsy specimens was determined by histologic examination, by rapid urease test (CLO test), or by PCR. Each patient underwent serological examination using three assays: (1) HM-CAP H pylori EIA test (EPI, Enteric Products Inc.). A titer of 2.2 or greater arbitrary EIA units was regarded positive; (2) FLEX PACK HP test (Abbott Laboratories). Readings were performed after four minutes of incubation; (3) Chiron RIBA H pylori 1.0 SIA ASSAY (Chiron Corporation). Antibodies were assayed against an HP bacterial lysate, as well as the CagA and VacA proteins.TableSixteen of 21 patients had HP detected in gastric mucosa. The FLEX PACK assay was significantly less sensitive than either the Chiron lysate or HM-CAP in detecting HP antibody. While both tests had a similar sensitivity, the lysate was twice as specific. Six of 21 (29%) patients had antibodies to either CagA or VacA. These 6 patients were detected by the Chiron lysate and HM-CAP, but the FLEX PACK assay failed to detect 2 (33%). Conclusions: (1) The Chiron lysate and HM-CAP are equally sensitive in detecting HP antibody but the lysate assay is twice as specific; (2) the FLEX Pack assay is significantly less sensitive than the other two assays; (3) 29% of pediatric patients with abdominal pain have antibodies to CagA or VacA. These patients are accurately detected by Chiron lysate or HM-CAP assays, but not by FLEX PACK.