Validation of a gastro-oesophageal reflux disease (GERD) specific screening instrument for epidemiological purposes

Abstract

INTRODUCTION: The prevalence of GERD is increasing worldwide; its community prevalence in Sri Lanka is unknown. AIMS: To develop a clinical score to screen for GERD in the community and assess whether a score using both symptom frequency and severity correlates better to an objective measure of GERD than one using only symptom frequency. METHODOLOGY: 58 GERD patients (endoscopy positive) and 60 controls (matched for age and gender) were given a GERD-specific interviewer-administered questionnaire assessing seven upper gastrointestinal symptoms. Each symptom was graded using Likert scales for frequency (4-items) and severity (5-items), and two scores were generated. Score 1 was the sum of frequency of symptoms while score 2 was the sum of products of frequency and severity of each symptom. The patients then underwent oesophageal manometry and 24h pHmetry. Cut-off values were determined by constructing receiver-operating characteristic curves. RESULTS: For both scoring systems, mean scores of cases were significantly higher than controls (p=0.000). The cut-off for score 1 was > 11.50 (sensitivity 91.4%, specificity 85%, positive and negative predictive values 83.29% and 92.34%). The cut-off for score 2 was > 12.50 (sensitivity 96.6%, specificity 80%, positive and negative predictive values 81.06% and 92.32%). Both scores showed high reproducibility (intra class correlation coefficient scorel=0.94 and score 2=0.82). There was good correlation between both scores and 24-h pH parameters (Spearman rank correlation, p=0.01), but score 2 was significantly better. CONCLUSION: Our GERD questionnaire is valid, reproducible and showed better correlation with an objective test when both severity and frequency of symptoms were scored rather than frequency alone.