The symptom-association probability: an improved method for symptom analysis of 24-hour esophageal pH data.

BACKGROUND/AIMS: All methods currently used to quantify the temporal relationships between symptoms and episodes of gastroesophageal reflux, as assessed by 24-hour pH monitoring, have major shortcomings. The aim of this study was to develop and validate a simple, all-comprising statistical method to calculate the probability that gastroesophageal reflux episodes and symptoms are associated.

METHODS

The 24-hour pH signal was divided into consecutive 2-minute periods. These periods and the 2-minute periods preceding the onset of symptoms were evaluated for the occurrence of reflux. Fisher's Exact Test was then applied to calculate the probability (P value) that reflux and symptom episodes were unrelated. Finally, the symptom-association probability (SAP) was calculated as (1.0 - P) x 100%. The SAP values found in 184 24-hour esophageal pH tests were compared with the symptom index and the symptom sensitivity index.

RESULTS

Discordance between the SAP and the symptom index was found in 21 patients (11%) and discordance between the SAP and the symptom-sensitivity index in 28 (15%). False-positive and false-negative symptom index values occurred preferentially in patients with small and large numbers of symptom episodes during the test, respectively (P < 0.05).

CONCLUSIONS

The SAP is a single, simple, quantitative measure of the strength of the association between symptoms and reflux episodes that is devoid of the disadvantages inherent to previously used methods.