Optimal thresholds and discriminatory power of 48-h wireless esophageal pH monitoring in the diagnosisof GERD.

BACKGROUND

The discriminative power of 48-h wireless esophageal pH monitoring in the diagnosis of gastroesophageal reflux disease has not been clearly demonstrated, and the cutoff level for esophageal acid exposure generating the optimal sensitivity and specificity is unknown. SUBJECTS AND Patients with typical reflux symptoms and a distinct response to acid suppressive medication

METHODS

underwent upper GI endoscopy followed by 48-h wireless esophageal pH studies with the pH electrode placed 6 cm above the squamocolumnar junction. The results were compared to those obtained in 55 healthy controls. Sensitivity, specificity, and thresholds for esophageal acid exposure were analyzed using receiver operating characteristic (ROC) curves.

RESULTS

The patient population consisted of 64 patients, 25 women and 39 men, with a median age of 48 yr. Analysis of the area under the ROC curve showed that, for all patients as well as for subgroups of patients with (N = 33) and without (N = 31) esophagitis, the total percent time with pH <4 for the 48-h study period was the best parameter to discriminate patients from controls. Analysis of acid exposure for day 1, day 2, or using the day with the highest acid exposure did not improve the diagnostic accuracy. A test specificity in the range of 90-95% resulted in a cutoff level of 3.6-4.4% of the total time with pH <4 for the 48-h period. This threshold generated a test sensitivity of 59-64% in all patients, 76-79% for patients with esophagitis and 42-48% in patients with no esophagitis.

CONCLUSIONS

The total percentage of time that esophageal pH was less than 4 for the entire 48-h study period was the parameter that best discriminated patients with typical reflux symptoms from healthy controls, and to achieve a specificity of 90-95% a cutoff level of 4% is recommended. The low sensitivity of wireless pH recording in patients without erosive esophagitis substantially reduces the clinical value of the test.