To investigate the H. pylori eradication rate obtained by each second-line regimen, stratifying these results by the first-line treatment previously used.

To study the effect on the eradication success rate of different doses of the drugs used in the same type of therapy and the effect of the length of the therapies. Moreover, we will study the differences in the efficacy of treatments by sub-analysis of the following factors:

• the age of the participants (adults or children);
• the diagnosis (dyspepsia, ulcer, other);
• the geographical area where the studies were performed.