Narrow band imaging (NBI) uses light in the blue and green spectrum to differentiate areas of carcinoma from normal or inflammatory tissue. This tertiary referral head and neck unit in Spain used white light endoscopy as initial screening for all 587 lesions prior to NBI in the awake outpatient setting, and graded them using a recognised five stage NBI system. Of these, 480 underwent biopsy (under local anaesthetic), the remainder were kept under clinical surveillance for a minimum of four years. There were 4.7% excluded because of poor visualisation of the lesion due to bleeding or intense gag reflex.
All the lesions biopsied showed improvements in specificity, positive and negative predictive value and accuracy for NBI compared to standard white light endoscopy. Sensitivity was similar in both. The overall conclusion of this study is that a lesion with a positive NBI is 6.89 times more likely to develop an SCC than those with a negative NBI, whereas under white light this chance is only 2.43.
The authors admit their data is not as impressive as other published results which undertook NBI procedures under GA. A longer learning curve improved accuracy in NBI, with a plateau after 200 cases. This paper signals an interesting role for this technology in outpatient diagnosis and surveillance, particularly in view of the high negative predictive value in mild / moderate dysplasia. This could avoid unnecessary and repeated surgical procedures, with both implications in terms of morbidity for the patient and cost to the healthcare system.