Comparison Between Probe-based Confocal Laser Endomicroscopy, White-light Endoscopy and Virtual Chromoendoscopy (pCLE-GCEP)

• Percentage of accurate endoscopic diagnosis made with pCLE compared with histopathology diagnosis [ Time Frame: An average of 1 week for which histology report will be out for comparison ] [ Designated as safety issue: No ]
  For each patient, the minimum sites of pCLE examination must consist of 2 sites at antrum, 1 site at the incisura, 2 sites at the corpus, and 1 site at the cardia. When suspicious lesions are present, more sites of pCLE examination will be allowed. Each site of pCLE examination will be biopsied and sent for histology.The pCLE examination will be video recorded and interpretation will be done independently on a separate day from the endoscopy day.The analysis will be by per biopsy site matched with corresponding video sequence
  
  

Patients will be recruited from an ongoing study - Gastric Cancer Epidemiology, Clinical and Genetic Programme Cohort Study (GCEP). GCEP is a prospective cohort study aiming to enroll 3,000 Singapore- Chinese subjects aged >50 years, and offers screening by endoscopy and systematic follow-up for a minimum of 5 years. 20 patients will be randomized into two groups. All of them will be examined using four different endoscopy imaging technologies by one trained specialist. 10 patients will be in group A and another 10 patients will be in group B. Group A: WLE followed by AFI followed by NBI followed by pCLE. Group B: WLE followed by NBI followed by AFI followed by pCLE. The difference between two groups is the sequence of two endoscopy imaging modes - AFI and NBI. Diagnosis made during NBI and AFI must be made based on pre-defined criteria, and should not be influenced by the preceding imaging modality. To control for the possible bias on the third imaging modality caused by influence from the preceding imaging modality, patients are randomized to receive NBI before AFI or AFI before NBI.

Endoscopic diagnosis will be made for each suspected lesion with every imaging modality. The biopsy of lesions will be taken after pCLE examination is completed and sent for histology. In the absence of suspicious lesions, the area of examination will be as follows (as stated in main GCEP protocol):

• A1- lesser curvature of the antrum, within 2-3cm of the pylorus.
• A2- greater curvature of the antrum, within 2-3cm of the pylorus.
• IA- incisura angularis.
• B1- lesser curvature of the corpus, 4cm proximal to the angulus.
• B2- middle portion of the greater curvature of the corpus, 8cm from the cardia.
• Cardia (C) - within 1 cm below the OGJ (defined as the point where gastric folds disappear).

The results will be compared with the gold standard diagnosis - histopathology diagnosis. The sensitivity and specificity for each imaging tool will be calculated accordingly.