The Clinical Significance of a Prolonged Stable pH around 4.0 in 24-h pH Monitoring

Abstract

Esophageal acidity may remain stable for long periods at or near pH 4.0, potentially influencing the estimation of risk of esophagitis in esophageal pH monitoring assessment. Our aim was to determine the frequency and clinical significance of a prolonged stable pH around 4.0 (PSpH4) (pH 3.5-4.5) by retrospective examination of 503 pH records from children and by analysis of clinical information, pH parameters, motility studies, and esophageal biopsies. The frequency, duration, and proportion of total time with PSpH4 were quantified, and the ratio of the time for which the pH was < pH 4.0 during PSpH4 episodes to the total reflux time below pH 4.0 was calculated [stable/reflux (S/R) rate]. One hundred fifty-eight PSpH4 episodes were identified in 80 records. The average duration was 60 min and the S/R rate was 30%. Sixty-one percent of PSpH4 episodes started in the postprandial period (p < 0.05). Proportionally more episodes of PSpH4 occurred with an increased total percentage reflux time (p < 0.01). In recordings with PSpH4, the average number of reflux episodes remained normal, even when the percentage reflux time was > or = 10%. No correlation was shown between PSpH4 and esophageal dysmotility, esophagitis, cardiorespiratory symptoms, or prematurity. PSpH4 did not occur in recordings obtained after fundoplication. We conclude that PSpH4 is common and may result in an overestimation of risk of esophagitis. Qualitative assessment of pH monitoring is necessary along with conventional quantitative measurements.