(a) DNA with known NRAS mutation (extracted from the primary tumour of patient 2AAH) was serially diluted with 35 ng of the matched control DNA isolated from the lymph node of the same patient and every mixed mutant:wild-type sample was assessed using PrimePCR ddPCR assay. The blue markers indicate the concentration of mutant DNA (copies per μl) and the green markers indicate the concentration of wild-type DNA (copies per μl) in each sample. All error bars generated by QuantaSoft software represent the 95% confidence interval. Fractional abundance of the mutant DNA in a wild-type DNA background is shown at the bottom of the plot. (b) Table shows the list of mutations detected either in primary lesions, blood or sputum samples from two patients, analysed using NGS or PrimePCR ddPCR assay. (c) Mutant circDNA has been detected by PrimePCR ddPCR assay in blood and (d) sputum samples isolated from patients with known ATM, NRAS and IGF1R mutations. Fractional abundance of these mutations in primary tumours was 35%, 20% and 2% respectively. (e) BRAF mutation that was identified in pre-malignant AAH lesion was detected in DNA extracted from matched plasma and sputum species by ddPCR.