Diagnostic potential of circulating cell-free DNA in patients needing mechanical ventilation: promises and challenges.

Circulating cell-free DNA (cf-DNA) mainly comes from apoptotic cells and can reflect the extent of cellular damage. Increased plasma levels of cf-DNA have been found in many acute disorders, including septic and clinically ill patients, and usually correlate well with clinical outcome. Acute respiratory failure, the most frequent organ failure in ICU patients, can be related to various acute diseases that may cause cell death and release of DNA into the bloodstream. In a recent issue of Critical Care, Okkonen and colleagues evaluate levels of cf-DNA in plasma as a prognostic marker in patients needing mechanical ventilation. They report that plasma cf-DNA was higher than normal in patients with mechanical ventilation, and even higher in patients who eventually died compared to survivors. However, its usefulness as a death predictor may be limited in the heterogeneous group of mechanically ventilated patients, probably due to confounding effects of co-morbidities, among other factors.