The diagnostic value of soluble urokinase-type plasminogen activator receptor (suPAR) for the discrimination of vertebral osteomyelitis and degenerative diseases of the spine

Background There is still a challenge in discriminating between vertebral osteomyelitis and degenerative diseases of the spine. To this end, we determined the suitability of soluble urokinase-type plasminogen activator receptor (suPAR) and compared the diagnostic potential of suPAR to CRP. Methods Patients underwent surgical stabilization of the lumbar and/or thoracic spine with removal of one or more affected intervertebral discs, as therapy for vertebral osteomyelitis (n = 16) or for erosive osteochondrosis (control group, n = 20). In this prospective study, we evaluated the suPAR and CRP levels before (pre-OP) and after surgery (post-OP) on days 3–5, 6–11, 40–56, and 63–142. Results The suPAR levels in vertebral osteomyelitis patients were significantly higher than those from controls pre-OP, 3–5 days post-OP, and 6–11 days post-OP. Significantly higher CRP levels were observed in the vertebral osteomyelitis group than in the controls pre-OP and 6–11 days post-OP. Levels of suPAR and CRP correlated positively in all patients in the pre-OP period: r = 0.63 (95% CI: 0.37–0.79), p < 0.0001. The values for the area under the receiver operating characteristics curve (AUC) for pre-OP and the overall model post-OP were 0.88 (95% CI: 0.76–1.00) and 0.84 (95% CI: 0.71–0.97) for suPAR, 0.93 (95% CI: 0.85–1.00) and 0.77 (95% CI: 0.62–0.93) for CRP, and 0.98 (95% CI: 0.96–1.00) and 0.91 (95% CI: 0.82–1.00) for the combination of suPAR and CRP. The AUC for suPAR pre-OP revealed an optimum cut-off value, sensitivity, specificity, NPV, and PPV of 2.96 ng/mL, 0.69, 1.00, 0.80, and 1.00, respectively. For CRP, these values were 11.58 mg/L, 0.88, 0.90, 0.90, and 0.88, respectively. Conclusion The present results show that CRP is more sensitive than suPAR whereas suPAR is more specific than CRP. Moreso, our study demonstrated that improvement in the diagnostic power for discrimination of vertebral osteomyelitis and degenerative diseases of the spine can be achieved by a combination of both suPAR and CRP. Trial registration ClinicalTrials.gov, NCT02554227, posted Sept. 18, 2015, and updated Aug. 13, 2019