Circulating nucleic acids as liquid biopsies for disease prediction, screening and diagnosis

Liquid biopsy used molecular information in body liquid to perform early diagnosis, screening, monitoring, prognosis, and treatment of various diseases. Circulating free nucleic acids (cfNA) are important diagnostic biomarkers, providing a window to accurately and immediately observe the body’s vital activity status. With the development of gene sequencing technology and bioinformatics technology, genetic, epigenetic, and fragtomics alterations that can be detected in cfDNA, as well as the expression level of miRNA and cf-mRNA can be quantified, this can reflect its tissue origin, gene regulation, genome evolution, and disease pathogenesis. This review focuses on the clinical utility of cfNA in different body liquids (blood, urine, bile), and discusses the diagnostic efficacy and accuracy of cfNA as diagnostic biomarkers in a variety of diseases. Blood is widely used to diagnose various tissue lesions for liquid biopsies as a body fluid circulating throughout the body, reflecting the state of the entire body. Bile and urine, as local circulating body fluids, can better reflect the changing state of tissues around the biliary tract and tissues around the bladder, respectively. In addition, normalized sample preservation, cfNA extraction, and detection procedures will help the practical application of cfNA in the clinic.