University of Michigan
Department of Pediatrics
Evidence-Based Pediatrics Web Site

Question

• 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.¹ 
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.²  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.

Citation

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