Evaluation of the Helicobacter pylori stool antigen test for monitoring eradication therapy.

OBJECTIVE: We aimed to clarify the time course of the Helicobacter pylori stool antigen (HpSA) level during and after eradication therapy and to determine the appropriate time of measurement of HpSA to evaluate eradication. METHODS: The subjects were 47 patients who were positive for H. pylori. The patients underwent a 1-wk regimen of triple therapy. The outcome of the eradication therapy was judged by urea breath test, culture, and histology 6 wk after the end of treatment. The HpSA level was serially measured nine times from before therapy until 12 wk after the end of therapy. RESULTS: In the group with successful eradication, HpSA C became negative immediately after the end of therapy and the negativity persisted. In contrast, in the noneradication L Croup HpSA became negative immediately after therapy, but became positive again within 21 wk after the end of therapy. The mean absorbance value of the HpSA test on the 4th day after the initiation of eradication therapy was significantly higher in the noneradication group than in the group with successful eradication. The diagnostic accuracy of the HpSA test increased to greater than or equal to90% 2 wk after therapy and thereafter. Comparison of the diagnostic accuracy at 4 wk after the end of therapy showed no significant differences with that at 2, 6. 8, and 12 wk after the end of therapy. CONCLUSIONS: The course of the HpSA levels during and after eradication therapy in patients with successful eradication was quite different from that in noneradication patients. Measurement of HpSA was useful to evaluate eradication, and the appropriate evaluation of the outcome of treatment could be made as early as 2 wk after the end of therapy. (Am J Gastroenterol 2002;97:594-599. (C) 2002 by Am. Coll. of Gastroenterology).