Narrow band imaging does not improve colonoscopy miss rate

NEW YORK (Reuters Health) - Colonoscopy performed with narrow band imaging (NBI) does not improve the miss rate of colorectal neoplasms compared with conventional white light examination, according to a report in the October issue of Gut.

NBI uses a light source centered at blue and green that penetrates primarily the mucosa and submucosa, making surface microvessels visible as dark structures, the authors explain. Because the density and shape of microvessels change in neoplasms, NBI could aid in the diagnosis of neoplasms.

Dr. Tonya Kaltenbach and colleagues from Stanford University School of Medicine, Palo Alto, California, investigated the neoplasm miss rate during tandem colonoscopy using NBI or white light.

A repeat colonoscopy under white light was the reference standard. "We removed any identified lesion at the time of initial detection, such that the endoscopist performed the second examination in a colon putatively cleared of lesions," the researchers explain. "Hence, we defined a 'missed' lesion as one identified during insertion or withdrawal of the second examination."

There were 37 missed neoplasms in 34 patients, the authors report, and there was no significant difference in the rate of missed lesions between the NBI (12.6%) and white light groups (12.1%).

The characteristics of the missed neoplasms did not differ between the NBI and white light examinations, the report indicates.

The neoplasm detection rates did not differ between the NBI and white light colonoscopy exams, the investigators say. The overall adenoma detection rate was 49%.

In a multivariate model, lesion size, morphology, and quality of bowel preparation had no significant influence on the association of NBI with neoplasm miss and detection rates.

"We did not find NBI to significantly influence the likelihood of missing or detecting a colorectal neoplasm compared to white light," the researchers conclude. "The 12% miss rate observed in our study, however, is approximately half of that reported in a recent systematic review of the published literature on adenoma miss rate determined by tandem colonoscopy."

"Future larger, comparative studies of the diagnostic characteristics of specific colonoscope features such as wide angle of view or high definition, CT colonography and other candidate screening modalities are of interest to advance the efficacy of colorectal cancer prevention," they add.

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