Assessment of concordance of symptom reflux association tests in ambulatory pH monitoring

• Published in: Alimentary pharmacology & therapeutics Vol. 35; no. 9; pp. 1080 - 1087
• Main Authors: Kushnir, V. M., Sathyamurthy, A., Drapekin, J., Gaddam, S., Sayuk, G. S., Gyawali, C. P.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.05.2012; Blackwell
• Subjects: Biological and medical sciences; Digestive system; Esophageal pH Monitoring; Female; Gastroenterology. Liver. Pancreas. Abdomen; Gastroesophageal Reflux - diagnosis; Gastroesophageal Reflux - physiopathology; Humans; Hydrogen-Ion Concentration; Male; Medical sciences; Middle Aged; Pharmacology. Drug treatments; Retrospective Studies; Sensitivity and Specificity; pH; Evaluation; Symptomatology; Ambulatory; Surveillance; Concordance
• ISSN: 0269-2813; 1365-2036
• DOI: 10.1111/j.1365-2036.2012.05066.x

Summary Background Both simple proportions and statistical tests are utilised for symptom‐reflux association. We systematically compared three such tests in a clinical setting. Aim To compare the three commonly used symptom reflux association tests in a large cohort of patients undergoing ambulatory pH monitoring for the evaluation of oesophageal symptoms. Methods Ambulatory pH data from 772 symptomatic subjects (49.1 ± 0.5 years; 479 F) tested off therapy were assessed for acid exposure time (AET, elevated when pH <4 for ≥4%), symptom index (SI, ≥50% when positive), and symptom association probability (SAP) and Ghillebert probability estimate (GPE, P < 0.05 when positive). Test concordance and discordance were individually assessed; discordance between statistical tests was minor if one had P < 0.1 while the other was positive. Logistic regression determined independent predictors of test discordance. Results The SAP, GPE and SI were positive in 42.7%, 39.3% and 33.9% respectively. GPE performed extremely well compared to SAP (sensitivity 0.95, specificity 0.91), with major discordance in only 2.8%. Positive concordance was significantly higher when AET was abnormal. GPE underestimated symptom association compared to SAP, whereas SAP was subject to symptom over‐counting in 33.3% of discordant cases. GPE‐SAP discordance was associated with higher AET (7.5% vs. 5.1%) and more symptoms (19.3 vs. 10.7, P > 0.001 for each comparison with concordant tests); both remained significant on logistic regression analysis (P ≤ 0.003). SI was discordant with SAP when symptoms were extremely frequent (median 19, IQR 10–32) or limited (median 1, IQR 1–2), and concordant when median 6 symptoms (IQR 3–12) were recorded. Conclusions The GPE can be used interchangeably with SAP in symptom reflux association. SI has uncertain value with very high and very low symptom counts.