Table 3 DIAMOND inclusion and treatment protocol

1. When a patient visits the GP, the inclusion and exclusion criteria are checked.

2. When the patient meets the criteria, the GP informs the patient about DIAMOND. When the patient wants to participate, he or she provides an informed consent.

3. The GP hands out the patient the medication for step 1. The medication is packed in boxes and is provided to the GP at the start of the study. Each box contains all the medication steps for one patient. The patient numbers on the boxes are linked to the numbers on the randomisation list in a sealed envelope kept at the researchers' office.

4. A blood sample is taken.

5. The patient receives the first questionnaire from the GP to fill out at home. Other questionnaires are sent to patients (Table 4).

6. The patient is treated according to the treatment protocol (see Figure 1 and 2). If the symptoms continue or relapse within 8 weeks after starting the medication step, the patient starts with the next treatment step. It is possible to shorten the treatment steps into less than 4 weeks, for instance when the patient suffers from side effects. The patient and GP are advised to schedule a follow-up visit at 4 weeks, which should be cancelled when the complaints are resolved.

7. When symptoms continue or relapse after medication step 3, the GP can treat the patient according to their own judgement.

8. The GP and the patient are informed six months after inclusion about the treatment allocation and the test results from the blood sample (whether the patient was infected with Helicobacter pylori).