Background : Lacking an objective ‘gold standard’ for diagnosing dyspepsia, several symptom-based classifications have been suggested.

Aim : To assess if response to proton-pump inhibitor treatment could provide useful information for current or future dyspepsia classification.

Methods : Post hoc analyses of 829 patients treated with omeprazole or placebo in a randomized-controlled trial. The ‘true’ response to omeprazole (trial response minus placebo response) was assessed according to different classifications of dyspepsia and different symptoms.

Results : Symptoms described with the words ‘burning’ or ‘sour’ and patients with reflux-like dyspepsia demonstrated high response to omeprazole treatment, whereas patients with abdominal pain or ulcer-like dyspepsia responded unpredictably to omeprazole. The response to omeprazole in patients with epigastic pain was related to the pattern of other dyspeptic symptoms. Patients with heartburn or regurgitation overlapped extensively with patients with epigastric pain.

Conclusion : The study demonstrated significant problems in the current classification of dyspepsia: ‘the most bothersome symptom’ was not independently related to the omeprazole effect and, in patients with abdominal pain, the response to omeprazole was dependent on the presence or absence of other dyspeptic symptoms. The overlap of symptoms indicates that heartburn and regurgitation should be recognized as symptoms of dyspepsia in primary care.