Posttreatment follow-up of Helicobacter pylori infection using a stool antigen immunoassay

The Helicobacter pylori stool antigen enzyme immunoassay (HpSA) was evaluat ed during posttreatment follow-up of patients in a country with a very high prevalence of H. pylori infection. From among 273 dyspeptic individuals (1 8 to 55 years) initially recruited from a shantytown in Lima, Peru, 238 par ticipants who met the inclusion criteria and were suspected to be H, pylori positive based on C-14 urea breath test (UBT) results underwent endoscopy, Participants with endoscopy-proven infections received standard eradicatio n therapy and were monitored by UBT and HpSA at 1 month following treatment and at 3-month intervals for 9 months posttreatment, A second endoscopy wa s performed if UBT results showed evidence of treatment failure or H. pylor i recurrence, Biopsy results were considered the "gold standard" in all ana lyses. Among patients who underwent endoscopy, HpSA had a pretreatment sens itivity of 93%, Two-hundred thirty patients completed the treatment regimen , of whom 201 (93%) were considered to have had successful treatment outcom es based on a negative follow-up UBT, Thirty-two patients with UBT-defined treatment failures or H. pylori recurrences at any point during the 9-month follow-up underwent a second endoscopy, In the posttreatment setting, HpSA had an overall sensitivity of 73% and a specificity of 67%. Agreement betw een UBT and HpSA diminished throughout the follow-up. Among 14 participants in whom HpSA remained positive at 1 month following treatment despite UBT evidence of treatment success, 12 (86%) became HpSA negative within 3 month s posttreatment, Although this study confirmed the validity of the HpSA in the initial assessment of dyspeptic patients, the test demonstrated a reduc ed overall accuracy in the detection of treatment failures and H. pylori re currences during 9 months of posttreatment follow-up, Furthermore, in some patients it may take up to 3 months after successful eradication for antige n shedding to diminish to levels within the negative HpSA range.