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Intraluminal Impedance Measurement Is More Sensitive Than pH Probe In Detecting Reflux In Infants


  • In infants with clinical symptoms of reflux, is pH probe the most sensitive test for reflux?

Clinical Bottom Lines

  1. Gastroesophageal reflux is a clinical diagnosis.
  2. Most reflux in infants is nonacidic in nature.2
  3. Intraluminal impedance(IMP) is able to detect both acid and nonacid reflux with more sensitivity than pH probe.1
  4. In infants with symptoms of spitting, anti-acid therapy is unlikely to be of benefit given the likely neutral nature of refluxate.
  5. In infants with more severe symptoms, anti-acid medication may be of benefit to decrease any pain associated with acidic reflux.
  6. Allowing the infant to grow is the most appropriate intervention for reflux. For those infants who have severe symptoms such as apnea and life threatening events, surgical intervention may be necessary.

Summary of Key Evidence

  1. Measurement of gastric and esophageal pH in infants after normal feedings show that pH>4 for ~130min (range 29-212). Mean percentage time that esophageal pH was <4 was 6.89%. This increased to 17.81% when recalculated based on total time gastric pH<4. This resulted in twice as many infants diagnosed with reflux.2
  2. 50 infants (mean age 86d ± 57d) undergoing evaluation for reflux enrolled. Standard pH probe and IMP probe placed. Infants given regular feedings without anti-acid or GI motility medication.
  3. 318 hours of data recorded with 1887 episodes of reflux by IMP. 282 episodes had pH<4.
  4. pH probe detected 153 of the 282 episodes of acid reflux detected by IMP (sensitivity 54.3% & PPV 56.7%).1
  5. pH probe detected only 153 of 1,887 episodes of all reflux detected by IMP (sensitivity 8.1%).1
  6. Not sure how valid these results are with regards to healthy term infants. No data was available regarding severity of reflux symptoms or comorbidities of the 50 infants studied.

Additional Comments


  1. Wenzl TG, et al. Esophageal pH monitoring and impedance measurement: A comparison of two diagnostic tests for gastroesophagesal reflux. J Ped Gastro Nutr 2002;34:519-523.
  2. Wenzl TG. Investigating esophageal reflux with the intraluminal impedance technique. J Ped Gastro Nutr 2002;34:261-68.
  3. Washington N, et al. Dual pH probe monitoring versus single pH probe monitoring in infants on milk feeds: The impact on diagnosis. Arch Dis Child 1999;81:309-312.
  4. Mitchell DJ, et al. Simultaneous monitoring of gastric and oesophageal pH reveals limitations of conventional oesophageal pH monitoring in milk fed infants. Arch Dis Child 2001;84:273-76.

CAT Author: Pamela Davis, MD

CAT Appraisers: John G. Frohna, MD

Date appraised: April 7, 2003

Last updated June 16, 2003
Department of Pediatrics and Communicable Diseases
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