A Randomized Comparison Between White Light Endoscopy (WLE) and Bright Narrow Band Imaging (B-NBI) in Subjects Undergoing Upper Gastrointestinal Endoscopy

Background It is recognized that gastroscopy can miss intestinal metaplasia, dysplasia and early gastric cancer (EGC)[1-3]. This could conceivably be due to the fact that EGC, as well as premalignant changes, may only present as subtle mucosal changes on conventional white light endoscopy (WLE) and thus be easily missed.

Chromoendoscopy has been used routinely in some centers during upper gastrointestinal (UGI) endoscopy in an attempt to improve mucosal contrast and detect subtle mucosal lesions[4]. However, this is not the norm in most centers due to the inconvenience of dye spray. Narrow band imaging (NBI) facilitates the examination of the mucosal surface without a need for chromoendoscopy. It is based on the principle that the depth of penetration of light is wavelength dependent, with shorter wavelengths resulting in more superficial penetration i.e. blue light penetrates most superficially (mucosal imaging) while red light penetrates the deepest (submucosal imaging). In NBI a rotating interference narrow band filter is interposed after the xenon light source such that when the NBI mode is switched on, discrete blue and green wavelengths are used and this improves mucosal surface contrast and facilitates visualization of mucosal details[5]. Magnifying endoscopy (ME) is useful in assessing the gastric mucosal pit pattern and microvessel of gastric mucosal lesions, thus providing the possibility of predicting the histological nature of the mucosal lesion. Studies from Japan, a country with a high population risk for gastric cancer, which were based on preselected high risk patients or patients with known precancerous lesions or EGC, showed that NBI and NBI-ME could diagnose precancerous lesions such as intestinal metaplasia (IM)[6] as well as EGC[7-11].

However, there is a lack of published data on the clinical utility of NBI in the detection of gastric intestinal metaplasia, dysplasia and EGC in the unselected general population. A recent study from Singapore looked at the utility of NBI and NBI-ME in patients aged 35 to 70 years undergoing diagnostic UGI endoscopy and found that the detection rate of focal lesions was increased from 43.7% to 58.8% with NBI, compared to WLE. Among the additional lesions detected, NBI-ME identified 97.1% as IM, 1.4% as EGC and 1.4% as benign. The EGC was a synchronous cancer missed by WLE but detected by NBI[12].

The current NBI system is limited by the dark endoscopic view. This has the potential limitation of making the detection of subtle lesions more difficult and lesions could be missed. A new prototype NBI system has been designed that has a brighter appearance. This prototype bright NBI coupled with high definition resolution is likely to overcome this drawback of original NBI.

Hypothesis We hypothesize that bright -NBI is superior to WLE in detecting focal gastric lesions such as gastric intestinal metaplasia, dysplasia and EGC in subjects undergoing diagnostic upper GI endoscopy.