Comparison Between Probe-based Confocal Laser Endomicroscopy, White-light Endoscopy and Virtual Chromoendoscopy

The investigators hypothesis that

1. clinical applicability and overall diagnostic sensitivity and specificity of pCLE for diagnosing gastric preneoplastic and neoplastic lesions is acceptable
2. pCLE, as compared to white-light endoscopy (WLE), AFI and magnifying NBI has higher sensitivity and specificity for the diagnosing gastric pre-neoplastic and neoplastic lesions

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.

Eligibility Criteria:
Inclusion Criteria:

* The subject is Chinese
* The subject is greater than 50 years of age
* The subject satisfies one or more of the following criteria:

  * has (had) a history of dyspepsia of at least 4 weeks or more. Dyspeptic symptoms include bloating, epigastric discomfort and early satiety
  * has a family history of gastric cancer
  * has a medical condition for which an OGD is indicated.
* Has past history of intestinal metaplasia or dysplasia
* The subject must have personally signed and dated the patient informed consent form indicating that he/she has been informed of all pertinent aspects of the study.
* The subject must be willing and able to comply with scheduled visits and other study procedures

Exclusion Criteria:

* patients who cannot undergo gastroscopies
* have a personal history of stomach cancer or surgery
* any disabling illnesses
* are pregnant or breast-feeding
* have bronchial asthma or a known allergy to fluorescein
* have renal impairment with serum creatinine above the upper limit of normal
* have uncorrected coagulopathy or severe thrombocytopenia precluding biopsy
* unable to provide informed consent