A new eradication resistance index as a predictor of metronidazole-containing second-line treatment of Helicobacter pylori

It is helpful in clinical practice to predict the effects of eradication therapy on Helicobacter pylori.To develop a useful predictor of the response to metronidazole (MNZ)-containing second-line regimens by combining minimal inhibitory concentrations (MICs) of both amoxicillin (AMX) and MNZ, and the results of urea breath test (UBT) before the treatment.We enrolled 107 patients who showed eradication failure following first-line triple therapy with a proton pump inhibitor, AMX and clarithromycin. The eradication resistance index was defined as: [pre-treatment UBT result ( per thousand)] x [AMX MIC (microg/ml)] x [MNZ MIC (microg/ml)]. Second-line eradication therapy with lansoprazole, AMX and MNZ was administered for 1 week. Eradication was confirmed by the UBT.The eradication resistance index in subjects showing eradication failure and those showing successful eradication was 9.72 +/- 6.63 and 1.25 +/- 2.31, respectively (p0.001). When a cutoff value of 3 was used, the eradication resistance index predicted the response to therapy with a specificity of 93.8%, sensitivity of 81.8%, and accuracy of 92.5%.The eradication resistance index is a more useful predictor of response to MNZ-containing regimens for second-line treatment than only pretreatment UBT results or MNZ resistance.