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Evidence-Based Pediatrics Web Site

A Positive pH Probe Diagnoses Reflux in Pediatric Patients


  • In an infant in whom you suspect gastroesophageal reflux, are 24-hour pH probes a reliable diagnostic test?

Clinical Bottom Lines

  1. The reproducibility of 24 hour pH-probe monitoring was only 69%.  Consider repeating negative pH probes in patients with symptoms of GER, especially if the study was shorter than 24 hours.1
  2. A negative pH probe in a symptomatic child does not entirely eliminate the diagnosis of reflux.  However, it has a very high specificity so a positive result rules in the diagnosis of GER.  These characteristics result in a positive LR of infinity and a negative LR of 0.06, which is pretty useful.2

Summary of Key Evidence

  1. Twenty-six patients between the ages of 1 month and 18 years with symptoms of GER underwent pH monitoring over two consecutive 24 hour periods.
  2. pH probes were considered pathologic if the GER index (percentage of time with pH<4) was >4%.
  3. Eight patients had conflicting results.  Five patients had normal studies on day 1 and pathologic reflux on day 2.  Three patients had pathologic reflux on day 1 and normal studies on day 2.
  4. The false negative rate for day 1 was 19.2%.  The data are not detailed enough in the paper to permit further analysis.
  5. In another study, 17 patients under 2 years-old with reflux and six controls underwent 24-hour pH-probe monitoring.The gold standard used here is a positive radiographic study or a positive acid reflux test.
  6. 16/17 patients with GER documented radiographically or by positive acid reflux test had a positive pH probe, yielding a sensitivity of 94%.  None of the controls had a positive pH probe, for a specificity of 100%.

Additional Comments

  • Maneuvers that increase intra-abdominal pressure such as bending over or exercise may increase episodes of reflux.
  • There is an initial increase in bicarbonate-containing saliva following placement of a nasogastric tube, which can underestimate GER.


  1. Mahajan, et al.  Reproducibility of 24-hour intraesophageal pH monitoring in pediatric patients.  Pediatrics, 1998;101:260-263.
  2. Sondheimer J.  Continuous monitoring of distal esophageal pH: A diagnostic test for gastroesophageal reflux in infants.  Journal of Pediatrics, 1980; 96:804-807.
  3. Friesen, et al.  Accuracy and reproducibility of 12-hour esophageal pH monitoring.  Journal of Pediatric Gastroenterology and Nutrition, 1991; 12:166-168.

CAT Author: Cami Fituch, MD

CAT Appraisers: John G. Frohna, MD

Date appraised: December 21, 1998

Last updated June 14, 2003
Department of Pediatrics and Communicable Diseases
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