Fig. 2

ddMSP and qMSP analyses of DNA methylation in clinical sputum samples. a ddMSP analysis of sputum samples of 20 cancer-free controls (normal subjects, N) and 20 patients diagnosed with lung tumor (T) for DNA methylation of RASSF1A. Each well of the sputum samples contained at least 10,000 droplets, suggesting that the clinical sputum specimens could be successfully “read” by ddPCR. b ddMSP analysis of 29 genes in a training set of 127 lung cancer patients and 159 controls developed an epigenetic classifier consisting of four DNA methylation biomarkers. The epigenetic classifier produced 0.92 AUC with 86.6% sensitivity and 90.6% specificity for diagnosis of lung cancer. c The epigenetic classifier had higher accuracy (88.8 vs. 70.63%, p = 0.004) and sensitivity (86.6 vs. 44.8%, p < 0.001) compared with sputum cytology, whereas keeping a similar specificity (90.6 vs. 91.2%, p = 0.34)