TruePrime LB addresses current liquid biopsy sensitivity and specificity issues by using adapted amplification of cancer-specific, large-fragment, cell-free DNA based on primer-free technology that combines the enzymes TthPrimPol and Phi29 DNA polymerase. TruePrime-mediated circulating tumor DNA amplification specifically selects the larger, more cancer-specific DNA fragment-size population from human plasma. Consequently, TruePrime LB provides a method for assessing cancer genome information from all patients, regardless of tumor burden, with superior sensitivity and specificity. The kit also preserves the single-nucleotide variants (SNVs) and SNV frequencies across different sequencing technologies and allows the amplification of cell-free DNA to levels that permit sequencing. TruePrime LB offers a screening method for de novo detection of cancer or reoccurrence of cancer based on a threshold of amplified DNA obtainable within a certain reaction time frame.