The role of cell-free nucleic acid diagnostics in clinical chemistry and pathology

Blood-based nucleic acid analyses are among the most dynamic and promising areas in the field of molecular in vitro diagnostics. This special edition of J Lab Med highlights various applications of “cell-free” nucleic acid diagnostics that already play or in the near future will play an important role in clinical decision making. The requirements for laboratories planning to offer these technologies in patient care are also reported.

The analysis of cell-free fetal DNA (cffDNA) also referred to as “non-invasive prenatal testing” (NIPT) has already been the focus in J Lab Med some years ago (J Lab Med, Vol 36, 2012) and has now taken an important part in prenatal medicine with an estimated 20,000 tests in Germany last year. In this edition of the journal, Harasim et al. review the available NIPTs with particular attention on the quality of the currently used technologies and the professional medical care and counseling that is required according to the Genetic Diagnostics Act (GenDG) in Germany [1].

The analysis of cell-free tumor DNA (ctDNA) – commonly referred to as “liquid profiling” or “liquid biopsy”– is another important technique that is about finding its way into clinical routine. Hinrichsen et al. [2] and Heitzer et al. [3] address these technologies and applications in cancer detection, therapy stratification, monitoring of therapy response and minimal residual disease. In a recent, heavily debated decision, the German supreme authority for reimbursement evaluation in statuary health insurance (Gemeinsamer Bewertungsausschuss) explicitly excluded the analysis of cell-free DNA in the just revised catalog of medical laboratory services. Considering the rapidly growing evidence for the clinical utility of ctDNA monitoring, this decision is hard to understand.

Further contributions in this edition address the clinical relevance of epigenetically modified nucleic acids such as methylated DNA as well as small non-coding miRNAs in serum, plasma and in tumor-derived exosomes that contain important diagnostic and prognostic information for cancer disease management [4, 5].

There is recently also growing evidence that nucleic acids trigger a variety of cellular processes as a reaction to viral and bacterial infections when foreign DNA and RNA are recognized as pathogen-associated molecular patterns (PAMPs) [6]. In addition, nucleic acids can elicit signals in immune cells during non-infectious conditions as danger-associated molecular patterns (DAMPs). The mechanism of nucleic acid sensing, triggering of cellular signaling pathways and therapeutic targeting are outlined in Hartmann’s review [6].

When new technologies arrive in patient care, an efficient and safe quality management is absolutely essential. While the results of a first ring trial scheme have been communicated by the Reference Institute for Bioanalytics (RfB), a notified body for external quality assessment in Germany, such schemes need further development. Schenk, who, together with Harasim, was the first to succeed in achieving a medical accreditation for a NIPT procedure in Germany by the DAkkS (the German accreditation body), provides a comprehensive summary on the different aspects of quality management and accreditation in cffDNA [7].

According to Dennis Lo, Professor for Chemical Pathology at the Chinese University of Hong Kong and one of the pioneers of the analysis of cell-free DNA, cell-free DNA will be the most prevalent analytical compartment in Clinical Chemistry and Pathology 10 years from now [8]. To address these developments, the German Society of Clinical Chemistry has launched the initiative “Task Force Liquid Profiling” that targets the entire spectrum of nucleic acids analyses in blood. The objectives of the Task Force are outlined at the end of this issue [9].

We hope that you enjoy with us this special edition of J Lab Med covering the wide range of blood-based nucleic acid diagnostics and thank all the contributing authors.