Infectious Lab Markers for Paraspinal Abscess
For suspected paraspinal abscess, the essential infectious lab markers to draw include erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), white blood cell (WBC) count with differential, and blood cultures. 1
Primary Laboratory Markers
Erythrocyte sedimentation rate (ESR): Highly sensitive marker that is typically elevated in spine infections including paraspinal abscesses. Patients with elevated ESR may be at increased risk for epidural abscess, which can often accompany paraspinal abscess. 1
C-reactive protein (CRP): Important inflammatory marker that rises rapidly in response to infection and is more specific than ESR. The combination of elevated ESR and CRP significantly increases the suspicion for spine infection with paraspinal involvement. 1, 2
White blood cell (WBC) count with differential: May show leukocytosis, though this finding can be less consistent than ESR and CRP elevation in spine infections. The differential can help identify the predominant inflammatory cell type. 1, 2
Blood cultures: Essential to identify potential causative organisms before initiating antimicrobial therapy. Should be obtained before starting antibiotics whenever possible to increase yield. 1
Additional Testing Based on Clinical Context
Fungal cultures and serology: Consider in immunocompromised patients or those with risk factors for fungal infections. 1
Mycobacterial testing: Including tuberculosis cultures and testing should be performed in patients from endemic areas or with risk factors for tuberculosis. 1
Brucella serology and cultures: Important in patients from endemic areas or with risk factors for brucellosis. 1
Special Considerations
Biopsy specimens: When image-guided aspiration is performed, material should be sent for:
- Gram stain and aerobic culture
- Mycobacterial stain and culture
- Fungal stain and culture
- Pathology examination 1
Molecular diagnostic tools: PCR techniques can improve the yield of microbiologic diagnosis, especially in patients who have received prior antimicrobial therapy. 1
Risk Factors That Should Prompt More Extensive Testing
Intravenous drug use: Associated with higher risk of multifocal spine infection and unusual pathogens. 1
Immunocompromised status: Including diabetes mellitus, HIV, cancer, or patients on dialysis. 2
Recent spine procedures: Including surgery, pain injections, or other interventions. 1, 3
Geographic considerations: Endemic infections such as tuberculosis, coccidioidomycosis, or brucellosis require specific testing. 1
Clinical Pitfalls to Avoid
Relying solely on WBC count: May be normal in up to 40% of patients with spine infection, making ESR and CRP more reliable markers. 1, 2
Delaying diagnosis: Paraspinal abscesses can present with nonspecific symptoms, leading to delayed diagnosis and increased morbidity. Early laboratory evaluation is crucial when clinical suspicion exists. 4, 5
Failing to correlate with imaging: Laboratory markers should be interpreted in conjunction with appropriate imaging (MRI with contrast being the gold standard with 96% sensitivity and 94% specificity). 1, 6
Missing multifocal infection: Patients with risk factors like IV drug use may have multiple sites of infection that require comprehensive evaluation. 1
Remember that while laboratory markers are important for diagnosis, they must be interpreted in the context of clinical presentation and imaging findings to accurately diagnose and manage paraspinal abscesses. 1