Evaluation of the Helicobacter pylori stool antigen test (HpSA) for detection of Helicobacter pylori infection in children

OBJECTIVE: Helicobacter py]ori (Ei. pylori) infection is usually acquired i n early childhood. Noninvasive methods for detection of H. pylori infection are required to study its incidence, transmission, and clearance. They sho uld be easy to perform, inexpensive, and have a high diagnostic accuracy, e specially in infants and toddlers. Both serology and the C-13-urea breath t est (C-13-UBT) do not fulfill all these requirements. The aim of this study was to evaluate a new enzyme immunoassay for detection of I-I. pylori anti gen in stool (Premier Platinum HpSA, Meridian Diagnostics, Cincinnati, OH) in a large cohort of children and to compare it to invasive techniques and the C-13-UBT. METHODS: HpSA was performed in 310 stool samples of 274 children divided in to three groups. Group A consisted of 145 children and adolescents: (0.5-19 .8 yr, 66/145 <6 yr) who underwent upper endoscopy for various gastrointest inal symptoms. H. pylori status was defined by histology, culture, and rapi d urease test from biopsies of the antrum and corpus. A C-13-UBT was perfor med in 133 of 145 children. Group B consisted of 22 patients (5.7-16.1 yr) who were retested with both noninvasive tests 8 wk after anti-H. pylori tri ple therapy. Group C consisted of 129 healthy infants and toddlers (0.9-3.1 yr) who were tested with the C-13-UBT. Children with discrepant or positiv e test results were retested after 2 and 12 months. Results of the HpSA wer e read at 450/620 firn by spectrophotometry. An optical density <0.100 was defined as negative, >0.120 as positive, and values between 0.100 and 0.120 were considered as equivocal. RESULTS: In Group A, the HpSA Save false-negative results in five of 45 inf ected children and false-positive results in four of 100 noninfected childr en, whereas four patients (2.8%) showed equivocal results. In both infected and noninfected children, no relation between the optical density values a nd age was found. The C-13-UBT was correct in 132 of 133 children tested. I n Group B, there was complete concordance between the HpSA and C-13-UBT: 19 children tested negative and three positive. In Group C, concordant result s between the two noninvasive methods were found in 124 of 129 (96%) toddle rs (122 negative and two positive). Retesting of five children with discrep ant results revealed that, on initial testing, the HpSA was incorrect in tw o tone false-positive, one false-negative), and the C-13-UBT was incorrect in three (always false-positive). CONCLUSIONS:In symptomatic children, the HpSA revealed a sensitivity of 88. 9% (95% CI 77.3-96.3) and a specificity of 94.0% (88.1-97.7) compared to th e C-13-UBT, 100% (94.0-100) and 98.9% (94.7-100), respectively. However, in healthy toddlers, the HpSA performed as well as the C-13-UBT with excellen t concordance between the two noninvasive tests. There was no age dependenc y of the stool test results, and changing the cutoff would not have improve d accuracy. Thus, the HpSA test seems suitable to monitor the success of an ti-H. pylori therapy. (C) 2001 by Am. Cell. of Gastroenterology.