The present invention provides a method of determining integrity and/or quantity of cell free DNA (cfDNA) in a bio logical sample comprising amplifying target sequences with at least a first primer/probe set and at least a second primer probe/set, amplifying the target sequences of differing lengths, and monitoring for detection of the labels of the oligonucleotide probes, and determining the integrity and/or quantity of the cfDNA based on the level of detection of the label of the oligonucleotide probe from the first primer/probe set compared to the level detection of the label of the oligonucleotide probe from the second primer/probe set. The present invention also provides methods for generating a library with the cfDNA for sequencing and analysis.