Verification and Progress of Cytokine Profiles and suPAR for the Discrimination of Infectious and Non-infectious, Degenerative Diseases of the Spine

Spondylodiscitis is a primary infection of the intervertebral discs with secondary infection of the adjacent end-plates and vertebral bodies. It is relatively rare with an incidence of 2.4:100.000 and three times more common among men. The process of infection, which is commonly creeping, leads to a destruction of the vertebral bodies and production of abscesses, which can cause neurological deficits.

Clinical symptoms, especially in the early stages, are uncommon. Patients suffer from unspecific back pain and fever occurs only in 50% of all cases. Currently, markers used including leucocyte count, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are also unspecific.For this reason of that several weeks may elapse between the first signs of symptoms and the final diagnosis of spondylodiscitis. Therefore, the identification of the pathogen is indispensable for an effective antibiotic therapy.

Spinal infections are generally monomicrobial, frequently with a haematogenous source. Therefore, blood cultures can be used for identifying the pathogens. In case of negative blood cultures, the pathogens can be identified by invasive methods such as percutaneous punch biopsy or CT-guided fine needle aspiration. Despite biopsies, the pathogen can only be identified in two out of three patients. Failures of pathogen identification are mainly due to previous systemic antibiotic treatment. As a consequence, diagnosis is often based on medical imaging methods (CT, MRT, PET, radiograph, skeletal scintigraphy). The disadvantage of these methods is that structural changes of the spine must occur to become visible.

Treatment of an advanced spondylodiscitis consists of removal of the necrotic tissue, stabilization of the affected vertebral bodies and concomitant antibiotic therapy. Randomized studies for the duration of antibiotic treatments have not been published as yet. Current recommendations are between 6 to 12 weeks. For evaluating the therapy response only the clinical improvement and the CRP value are used. The mean period of stay in the hospital is about 49 days.

The goal is to establish a non-invasive method which allows discrimination of infectious and non-infectious diseases to improve the diagnosis of spondylodiscitis. For that purpose, blood and tissue samples from patients with spondylodiscitis and erosive osteochondrosis will be collected and analyzed for their cytokine and suPAR concentration. Erosive osteochondrosis is a non-infectious, degenerative disease of the spine with similar surgical treatment. Thus, it is an optimal reference group. Nevertheless, erosive osteochondrosis includes special types, called modic type I-III. Because modic type I is associated with an immune response caused by repeated traumata of the spine this modic type will be excluded from the study.