Analysis of cell‐free circulating DNA fragment size and level in patients with lumbar canal stenosis

Cell‐free circulating DNA (cfDNA), extracted by liquid biopsy, has been studied as a noninvasive biomarker for various diseases. The potential of cfDNA fragment size and level as a marker in lumbar canal stenosis (LCS) patients has never been studied. We investigated whether cfDNA is a biomarker of low back pain, leg pain, leg numbness severity in patients with an LCS. Blood samples were obtained from patients with LCS (n = 22) before and immediately after spinal surgery. Plasma DNA was isolated and examined for cfDNA fragment size and concentration. A cohort of healthy volunteers (n = 5) constituted the control group. The cfDNA fragment size tended to be shorter in patients than in healthy controls, but this difference was not significant (P = .186). cfDNA level was significantly higher in LCS patients (mean 0.614 ± 0.198 ng/μL, range 0.302‐1.150 ng/μL) than in healthy controls (mean 0.429 ± 0.064 ng/μL, range 0.366‐0.506 ng/μL) (P = .008). cfDNA level correlated positively with average pain (r = .435, P = .026) and leg numbness (r = .451, P = .018). cfDNA fragment size did not differ from before to after surgery, but cfDNA level increased postoperatively in patients with LCS. This was the first study investigating whether cfDNA fragment size and level are associated with pain in patients with LCS. Our findings suggest that cfDNA level may be an objective indicator of pain and surgical invasiveness in patients with LCS.