Neutrophil to lymphocyte ratio and mortality in spinal epidural abscess

Background context: Neutrophil to lymphocyte ratio and platelet to lymphocyte ratio have been previously identified as markers for overall survival in oncology but remain heretofore unexplored in spinal epidural abscess (SEA).

Purpose: The purpose of this study was to determine the impact of these routinely collected assessments on 90-day mortality in SEA.

Study design/setting: Retrospective, case-control study.

Patient sample: Patients 18 years or older diagnosed with SEA at 2 academic medical centers and 3 community hospitals.

Outcome measures: Ninety-day postdischarge and in-hospital mortality.

Methods: Complete blood count with differential obtained on the day immediately preceding or on the day of admission was used to calculate platelet to lymphocyte and neutrophil to lymphocyte ratios. Multivariate analyses were used to determine if these ratios were independent risk factors for 90-day mortality.

Results: For 1,053 SEA patients included in the study, the rate of 90-day mortality was 134 (12.7%). The rate of 90-day mortality with neutrophil to lymphocyte ratio (≥8) was (20.5%) compared to (8.1%) with neutrophil to lymphocyte ratio <8. Neutrophil to lymphocyte ratio was positively associated with bacteremia, elevated erythrocyte sedimentation rate, and concurrent systemic infections (endocarditis, meningitis) and negatively associated with duration of symptoms prior to presentation. On multivariate analysis, elevated neutrophil to lymphocyte remained an independent risk factor for 90-day mortality (odds ratio=2.62, 95% confidence interval=1.66-4.17, p<.001). Platelet to lymphocyte ratio was not associated with 90-day mortality.

Conclusions: Absolute neutrophil to lymphocyte ratio is a routinely collected but overlooked biomarker in patients with spinal epidural abscess that is a novel independent risk factor for 90-day mortality.