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, I 2 = 23%). The area under the summary receiver operating characteristic curve was 0.699. Sensitivity was 0.903 (95% CI, 0.84‐0.94, I 2 = 54%), and specificity was 0.68 (95% CI, 0.60‐0.75, I 2 = 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.