Methylene Blue as a Diagnosis and Screening Tool for Oral Cancer and Precancer

Objectives: To evaluate the accuracy of methylene blue (MB) for diagnosing oral cancer and precancer. Data Sources: PubMed, Cochrane Database, Embase, Web of Science, SCOPUS, and Google Scholar. Review Methods: Two authors working independently reviewed 6 databases from their dates of inception until April 2020. Studies exploring oral mucosal disorders as detected by MB were assessed. True-positive, true-negative, false-positive, and false-negative data were extracted for each study. Methodological quality was evaluated with the Quality Assessment of Diagnostic Accuracy Studies tool (v 2). Results: Seven prospective and retrospective studies (N = 493) were included. The diagnostic odds ratio of MB was 20.017 (95% CI, 10.65-37.63, I² = 23%). The area under the summary receiver operating characteristic curve was 0.699. Sensitivity was 0.903 (95% CI, 0.84-0.94, I² = 54%), and specificity was 0.68 (95% CI, 0.60-0.75, I² = 0%). The correlation between the sensitivity and the false-positive rate was –0.17, indicating an absence of heterogeneity. Conclusions: Regarding diagnostic accuracy, MB had high sensitivity but low specificity, suggesting that it cannot be recommended as a replacement for the currently used standard of a scalpel biopsy with histologic assessment. Instead, it should be used as an adjunct to conventional assessment because of its low toxicity and price.