The T2-FLAIR mismatch sign as a predictor of IDH-mutant, 1p/19q-noncodeleted lower-grade gliomas: a systematic review and diagnostic meta-analysis

Objectives To evaluate the diagnostic performance of the T2-FLAIR mismatch sign for prediction of isocitrate dehydrogenase ( IDH )-mutant, 1p/19q-noncodeleted lower-grade gliomas (LGGs) and review studies with false positive results. Methods The MEDLINE and EMBASE databases were searched up to March 13, 2020, to identify articles reporting the diagnostic performance of the T2-FLAIR mismatch sign for prediction of IDH -mutant, 1p/19q-noncodeleted LGGs ( IDH mut-Noncodel) using the search terms (T2 FLAIR mismatch). Pooled sensitivity, specificity, and correlation coefficient for interobserver agreement were calculated. Results Twelve studies including a total of 1053 patients were included. The median age was 43 (median; range, 14–56). The pooled sensitivity and specificity were 42% (95% CI, 28–58%) and 100% (95% CI, 88–100%), respectively. According to the HSROC curve, the area under the curve was 0.77 (95% CI, 0.73–0.80). Considerable heterogeneity was possible among the studies in terms of both sensitivity and specificity. A threshold effect was suggested and was considered to explain most of the heterogeneity. Four studies reported false positive results for the T2-FLAIR mismatch sign, including dysembryoplastic neuroepithelial tumor, pediatric-type gliomas, and non-neoplastic lesions. The 2 original articles with false positive results showed the highest sensitivities among the 10 studies included in the quantitative analysis, supporting the probability of the threshold effect. The pooled correlation coefficient was 0.87 (95% CI, 0.73–0.94). Conclusions The T2-FLAIR mismatch sign had a high specificity and interobserver agreement for the prediction of IDH mut-Noncodel. However, the sign demonstrated low sensitivity, and a few studies with false positive cases were also reported. Key Points • The pooled sensitivity and specificity of the T2-FLAIR mismatch sign for prediction of IDH-mutant, 1p/19q-noncodeleted lower-grade gliomas were 42% and 100%, respectively. • Four studies reported false positive results. • The pooled correlation coefficient was 0.87, suggesting almost perfect interobserver agreement.