Dependability of esophageal pH monitoring data on software

Acid gastroesophageal reflux reports in infants: a comparison of esophageal pH monitoring and multichannel intraluminal impedance measurements

Twenty-four-hour tracings generated from combined esophageal pH and multichannel intraluminal impedance measurements of 14 infants (nine males, median age 3.5 months) were examined retrospectively. For each tracing, two acid reflux assessment reports were generated using either pH monitoring alone or pH monitoring combined with impedance. Significantly fewer acid reflux episodes were detected using pH monitoring combined with impedance when compared to pH monitoring alone (25.1+/-4.0 versus 99.9+/-18.3 episodes/patient, p=.001). Estimates of esophageal acid exposure using pH monitoring alone were two-fold higher (137.4+/-23.7 versus 66.6+/-15.9 min/patient, p=.002) than estimates derived using both techniques. Of the total acid reflux episodes detected by pH monitoring alone, 71.8% could not be confirmed by combined pH and impedance. Detection of significant numbers of "pH-only" episodes raises concerns regarding possible over-estimations of acid exposure that may occur when estimates are based solely on esophageal pH monitoring.

Glass and antimony electrodes for oesophageal pH monitoring in distressed infants: how different are they?

OBJECTIVE

Although antimony electrodes are by far the most popular for performing oesophageal pH monitoring, there are few data comparing the accuracy of glass and antimony electrodes. Therefore, we tested the accuracy of both electrodes in the prediction of oesophagitis.

METHOD

pH monitoring using a glass electrode and an antimony electrode was performed in 60 distressed infants, aged between 1 and 6 months. An upper endoscopy with oesophageal biopsies was also performed in all infants.

RESULTS

A reflux index (percentage of the total time with pH < 4.0) greater than 5% was considered to be abnormal and was found in 40/60 patients. Histological oesophagitis was present in 26/60 infants. The reflux index was > 5% with the glass electrode in 18/26 children with histological oesophagitis and with the antimony electrode in 10/26 children with histological oesophagitis. Histology of the oesophagus was normal in 22/40 children with abnormal pH monitoring. With the glass electrode, the mean reflux index in the group with oesophagitis was significantly higher than in the group with normal histology, although there was an important overlap. With the antimony electrode, the mean reflux indices in the groups with and without oesophagitis were not different. Regarding normal/abnormal, there was discordance in 35% of the pH studies. No reflux index could be related to a clinically useful sensitivity and specificity to predict oesophagitis.

CONCLUSION

The reflux index does not accurately predict oesophagitis. Oesophageal pH monitoring and endoscopy provide complementary information.

Esophageal pH monitoring and impedance measurement: a comparison of two diagnostic tests for gastroesophageal reflux

BACKGROUND

pH monitoring is the standard diagnostic tool for gastroesophageal reflux in infants. However, this method does not document the reflux of all kinds of fluid from the stomach into the esophagus, but only documents acid material. The parameters that define reflux episodes by pH monitoring have been derived empirically from observations of many infants considered healthy and ill. Acid reflux is a continuum, some reflux is normal and doubt exists as to how much reflux is abnormal. In this study, one of the standardized protocols for analyzing pH recordings was evaluated and compared with simultaneously obtained intraesophageal impedance measurement (IMP), a pH-independent method of detecting bolus movement within the esophagus.

METHODS

The esophagi of 50 infants with reflux symptoms were measured, using both standard pH probe and multiple-site impedance measurement. A standard protocol for analyzing esophageal pH records was used. The sampling rate for pH values was 15/min. Acid reflux was defined as pH less than 4.0 (threshold pH) for at least 15 seconds (minimal duration) with at least 30 seconds (latency time) between separate episodes. The software used could adjust independently or in combinations the sampling rate and these reflux criteria. Thereby it was determined whether changes in the criteria for acid reflux improved the sensitivity and predictive value of pH monitoring when compared with reflux episodes defined by IMP.

RESULTS

During 318 hours of recording in 50 infants, 1,887 episodes of reflux occurred according to IMP. Only 282 (14.9%) of the IMP-determined episodes were acid reflux episodes. No alkaline reflux episodes occurred. Among the 270 pH probe-determined episodes using the standard criteria of acid reflux, only 153 (sensitivity, 54.3%; positive predictive value, 56.7%) were accompanied by unmistakable retrograde bolus movement using IMP measurements. Retrograde bolus movement did not accompany the other 117 episodes. Using a sampling rate of 15/min, a pH threshold of 4.0, a minimal duration of reflux episodes of 8 seconds, and a latency time of 60 seconds, the positive predictive value of pH probe results increased to 60.7%. Variations in the sampling rate or criteria for defining acid reflux did not significantly improve the accuracy of the pH probe results versus IMP-defined episodes.

CONCLUSIONS

Most reflux episodes that occur in infants are undetectable by standard pH probe monitoring. pH monitoring does not detect all reflux in the esophagus but is useful for detecting acidity in the esophagus and determining the duration of its presence. Combining pH monitoring with impedance measurement is a valuable diagnostic tool for gastroesophageal reflux in infants.