Correlation between Erythrocyte Sedimentation Rate/CRP Ratio and Procalcitonin Values in Postoperative Spondylodiscitis : Potential Biomarker Comparison.

Objective: Postoperative spondylodiscitis is a rare but serious complication of spinal surgery. The difficulty in establishing an early diagnosis necessitates the evaluation of novel biomarkers. This study aims to determine the diagnostic value of procalcitonin (PCT), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), ESR/CRP, and ESR/PCT ratios in the diagnosis of postoperative spondylodiscitis and to compare the sensitivity and specificity of these parameters.

Methods: This retrospective study was conducted by evaluating 55 patients who underwent two-level lumbar instrumentation (foraminotomy-medial facetectomy and microdiscectomy, autologous graft with fusion) between 2019 and 2023.. Laboratory values of 28 patients diagnosed with postoperative spondylodiscitis and 27 control patients with no signs of infection were analyzed. The cut-off values, sensitivity, specificity, positive and negative predictive values, and area under the curve (AUC) of CRP, ESR, PCT, ESR/CRP, and ESR/PCT ratios were calculated using receiver operating characteristic (ROC) analysis.

Results: CRP, ESR, and PCT levels were significantly elevated in patients with spondylodiscitis (p < 0.05). The ESR/PCT ratio demonstrated 96% specificity and was considered a supportive marker for the diagnosis of spondylodiscitis. However, the ESR/CRP ratio did not show a significant difference between the two groups (p = 0.222). The cut-off value for CRP was determined as 43.7 mg/L, with a specificity of 100%. The cut-off value for ESR was 46 mm/hour, with a sensitivity of 92.9%. The cut-off value for PCT was found to be 0.034 ng/mL, with a sensitivity of 96.2%.

Conclusion: CRP and ESR/PCT ratios were found to be effective in supporting the diagnosis of postoperative spondylodiscitis due to their high specificity. On the other hand, ESR and PCT demonstrated higher sensitivity, making them more successful in distinguishing non-infected individuals. However, no single biomarker was deemed sufficient on its own, emphasizing the necessity of clinical evaluation alongside laboratory findings. Prospective studies are needed in the future to enhance the diagnostic accuracy of these biomarkers.