Normal acid exposure time in esophageal pH monitoring in Asian and Western populations: A systematic review and meta-analysis

Background: Esophageal acid exposure time (AET) during 24 h pH monitoring is reproducible and predictive outcomes of treatment for gastroesophageal reflux disease. Several small Asian studies have investigated the normal range of the AET; the range may be different from that in Western populations. We evaluated its normal range in healthy Asian compared to Western subjects. Methods: We searched PubMed, Embase, Cochrane Library, and KoreaMed for studies that reported pH monitoring parameters in healthy subjects. Studies that reported the AET values of healthy subjects were eligible for the analyses. The upper limit of normal of the AET was obtained from the 95th percentile of the available raw data or calculated as the mean value +2 standard deviations. Key Results: Nineteen Asian and 49 Western studies were assessed. The estimated AET values were analyzed using a bootstrapping technique, weighted according to the sample size. The mean AET was 1.1% and 2.9% in the Asian and Western populations, respectively. The upper limit of the reference range was 3.2% (95% confidence interval [CI], 2.7–3.9%) and 8.2 (95% CI, 6.7–9.9) in the Asian and Western populations, respectively. The normal AET differed between the Asian and Western populations because the CI of the two groups did not overlap. Conclusions & Inferences: The upper limit of normal of the AET in healthy Asian subjects was 3.2% (95% CI, 2.7–3.9%), which was lower than that of healthy Western subjects.