evidence: Figure 1-left illustrates that the prevalence of pathologic 24-hour esophageal reflux in the index study was significantly higher (P = 0.0005, McNemar's Test) when measured as time pH < 4 than when measured as integrated acidity.
intervention:  integrated acidity
comparator: time pH < 4
outcome: the prevalence of both pathologic 24-hour and nocturnal esophageal reflux in the 3rd study