Beyond Cancer: cfDNA as a 'Severity Meter' in the ICU

When veterinarians hear "cell-free DNA," they almost immediately think of cancer screening. This is natural, as oncology drives the market. However, physiologically, cfDNA is much broader than that.

It is a marker of Cell Death.

In the Emergency and Critical Care (ECC) setting, we deal with diseases defined by massive cellular destruction: Sepsis, Trauma, GDV, and Pancreatitis. In these patients, cfDNA offers something unique: a quantitative "Severity Meter."

The Concept: "The Death Load"

Traditional markers like lactate measure anaerobic metabolism (function). Creatinine measures filtration (function). But cfDNA measures structure. It tells you how many cells have physically ruptured or died in the last few hours.

* Healthy Dog: ~0.5 – 1.0 ng/mL.
* Septic/Trauma Dog: Can range from 2.0 ng/mL to >50.0 ng/mL.

Evidence in Dogs

Research has validated this correlation in veterinary patients:
Trauma: Letendre & Goggs (2017)* found that dogs with blunt trauma had significantly elevated cfDNA compared to healthy controls. The level of cfDNA correlated with the Injury Severity Score (ISS).
GDV: Troia et al. (2018)* showed that dogs with Gastric Dilatation-Volvulus had median cfDNA levels of ~3,500 ng/mL (vs ~1,300 in their control group).

Clinical Utility: Triage and Trends

While cfDNA is not yet a standalone prognostic tool (in the Troia study, lactate was still a better predictor of survival), its value lies in monitoring.

Scenario: A dog is admitted with septic peritonitis post-surgery.
1. Admission: cfDNA is high (expected). You start antibiotics and drainage.
2. Day 1 Recheck: If the source of necrosis is controlled, cfDNA (with its 2-hour half-life) should plummet.
3. The Red Flag: If cfDNA remains persistently high despite normal lactate and stable vitals, it suggests occult ongoing necrosis—perhaps an undrained abscess or a new thrombus.

It provides a molecular look under the hood when the clinical picture is ambiguous.