A barium swallow or an Upper GI x-ray can make the diagnosis of reflux -- if the child happens to reflux during the snapshot. A ragged esophageal lining is sometimes seen between episodes, and that would be also be good evidence. A negative test doesn't tell you anything.

A pH probe is more likely to find reflux if it is present. Here a probe rests in the esophagus and detects acid that may slosh there through the course of an entire day. But some kids don't slosh every day.

Looking directly at the esophageal lining (with a scope) is the most reliable, but most invasive. It usually involves snipping a tiny bit of lining to look at under a microscope if any question remains.

Often the diagnosis is made based on the story and physical exam alone. Improvement of symptoms with reflux treatment adds weight to this type of diagnosis.