Plasma cell-free DNA as an indicator of severity of injury in burn patients

Background: Raised levels of plasma cell-free DNA have been detected in various patient groups, including trauma patients. We hypothesized that plasma DNA is increased in burn patients and may represent an objective indicator of burn severity and have predictive as well as prognostic significance. Methods: This was a prospective clinical study with full ethical approval. With informed consent, blood samples were collected from 28 burn patients within 24 h of injury and from 12 control subjects. Plasma cell-free DNA was measured by real-time quantitative polymerase chain reaction (PCR) assay for the beta-globin gene. Descriptive analysis, non-parametric data comparison tests (Mann-Whitney) and correlation tests (Spearman rank) were performed on the data. Results: Samples were taken at a mean time of 5.7 h after injury from 13 patients with flame/flash burns and 15 patients with scalds. Median plasma DNA levels in the control, scald and flame/flash burn patient groups were 287, 648 and 2685 kilogenome-equivalents/L, respectively. Plasma DNA levels correlated with the length of hospital stay, but not with admission to the intensive care unit (ICU) nor the length of ICU stay. DNA levels correlated with the burn surface area (Spearman rank r=0.54, p=0.04) and the number of operations needed (Spearman rank r=0.55, p=0.03) for scalds, but not for flame/flash burns. Conclusions: Plasma DNA is increased after burn injury and is significantly correlated with some outcome measures, including the length of hospital stay. DNA levels are higher in flame/flash patients than in scald patients; the difference may provide an objective indication of burn depth and inhalation injury.