Percentage of time versus surface above cut-off in the analysis of bile reflux monitoring in man.

Recent studies, using ambulatory optical monitoring of esophageal bilirubin concentration (Bilitec), have suggested that reflux of both acid and duodenal contents frequently occurs in patients with gastro-esophageal reflux disease (GERD). In in vitro studies, it was observed that a linear correlation exists between fiberoptic absorbance and bilirubin concentration, and that bilirubin concentration is an adequate marker for quantifying duodenogastroesophageal reflux. It seems logical, therefore, to assume that the surface above the cut-off level for bilirubin absorbance would provide an adequate quantitative marker for reflux of duodenal contents. Aim; To study whether the surface above cut-off during Bilitec monitoring has a better correlation with esophageal lesions and pH measurement than % of time above cut-off level. Method~: In 84 patients (46 men, mean age 46 -+ 2 years) evaluated for suspected gastro-esophageal reflux disease, we performed an upper gastrointestinal endoscopy and an ambulatory 24 hours esophageal pH and Bilitec monitoring. All drugs potentially affecting gastrointestinal motility and acid secretion were discontinued at least one week prior to the study. We calculated both the % of time and the surface of bilirubin absorbance above cut-off level of 0.14. We also calculated the % of time of pH < 4 and the surface of acid reflux. Results (mean .+ SEM) were compared by Student's ttest. Results: : The endoscopy revealed no esophagitis in 45 patients (54%), grade 1 or 2 esophagitis in 23 patients (27%) and grade 3 or 4 esophagitis in 16 patients (19%). The % of time that bilirubin absorbance was above 0.14 was 6.1 .+ 1.5 in patients without esophagitis, 8.5 -+2.6 in patients with esophagitis grade 1 or 2, and 16.1 _+ 4.2 in patients with esophagitis grade 3 or 4 (p=0.006 compared to no esophagitis). A pathological Bilitec monitoring (% of time above 0.14 > 4.6) was present in 34 patients (40%). A poor but significant correlation was present between the pH measurement (% of time pH < 4) and Bilitec monitoring (R=0.40, p < 0.05). The surface of bilirubin absorbance>0.14 was 7.8-+ 2.3 abs*min in patients without esophagitis 12.1 ± 4.5 abs*min in patients with esophagitis grade 1 or 2, and 18.1 ± 4.6 abs*min in patients with esophagitis grade 3 or 4 (p=0.03 compared to no esophagitis). The correlation between the pH measurement (% of time pH < 4) and Bilitec monitoring was not improved by considering the surface of bilirubin absorbance above cut-off level (R=0.47, p < 0.005). Taking into account the surface of acid reflux also failed to improve the correlation with the surface of bilirubin absorbance above cut-off level (R=0.32, p=0.03). Conclusions: Taking into account the surface rather than the % of time above the cut-off level for bilirubin absorbance does not improve the correlation of Bilitec with acid reflux and with esophageal lesions. Bilirubin concentraction, reflected as bilirubin absorbance, may not be directly proportional to the caustic factor in duodeno-gastro-esophageal reflux