Table 2. Qualitative comparison of tissue biopsy and liquid biopsy.

Tumor	Sample size	Sensitivity	Specificity	Positive predictive value	Negative predictive value	Reference
NSCLC	216	0.70	0.69	0.86	0.46	Oxnard 2016 (23)
NSCLC	2012	0.67	0.94	not stated	not stated	Luo 2014 (24)
mKRK	98	0.90	0.93	0.94	0.90	Schmiegel 2017 (25)

Different tumor entities, such as non–small cell lung cancer (NSCLC) or metastatic colorectal cancer (mCRC) shed different amounts of circulating free deoxyribo?nucleic acids (ctDNA) into the bloodstream. Based on the statistical quality parameters sensitivity (correct positive rate), specificity (correct negative rate), positive (accuracy) and negative predictive value (discriminatory power), the benefits of liquid biopsies compared to tissue biopsies can be evaluated on an individual basis. This study shows that in NSCLC a complete transition from tissue biopsy to liquid biopsy would result in a substantial reduction in diagnostic care quality. Given its advantages and its high positive predictive value, liquid biopsy is complementary to tissue biopsy in this setting.