Ph paper test strips

We employed both white light endoscopy (WLE) using a Pentax EG-2990i instrument, and endoscope-based confocal laser endomicroscopy (CLE) using a Pentax EC 3870CLK instrument. A full assessment of the upper gastrointestinal tract was carried out first using WLE according to a standard protocol. Gastric fluid was aspirated for pH determination, using pH paper test strips (Sigma Chemical Company St Louis, USA). Hypochlorhydria was defined as gastric pH>4. CLE was used to image the antrum after administering 5–10 ml of 2% fluorescein sodium intravenously [17 (link)]. The antrum was carefully mapped into eleven distinct areas for CLE and biopsy: Areas 1, 2 and 3 were on the incisura, areas 4, 5 and 6 were between the incisura and the pyloric opening, and areas 7, 8 and 9 were on the greater curve of the antrum. Area 10 was near the antral-corporal junction on the greater curve, and area 11 was proximal to the incisura. S1 Table shows how our mapping compares with the systemic alphanumeric-coded endoscopy (SACE) [21 (link)]. Between 10 and 30 CLE images were obtained from each site, an average of 200 per patient, and all images free of motion artefact were saved. Non-targeted biopsies were obtained from areas 1, 2, 3 and 5 in separate formalin containers.

The study was conducted between July 2016 and November 2017 at the University Teaching Hospital (UTH) endoscopy unit in Lusaka, Zambia. All consenting adults above the age of 18 years were considered for recruitment. All participants gave written and well informed consent. Excluded were those with large bleeding oesophageal varices, occluding oesophageal lesions and previously confirmed or treated for gastric or oesophageal cancer. These patients all fasted overnight prior to the procedures. During the oesophagogastroduodenoscopy (OGD), contents of the biopsy channel were cleared and gastric juice aspirated using a 10 ml syringe. Aspiration of gastric juice was done immediately upon entering the stomach. The rest of the upper gastrointestinal tract was then examined following the standard of care. Biopsies were taken from mucosal lesions seen. After the OGD, gastric juice pH was measured using pH paper test strips (Sigma Chemical Company St Louis, USA). An aliquot of the juice was saved at -80°C for further experiments.