How nonbacterial osteomyelitis could be discriminated from tuberculosis in the early stages: the simple algorithm

Chronic nonbacterial osteomyelitis (CNО) and tuberculous osteomyelitis (TBO) are both primarily chronic inflammatory bone diseases with similar clinical and radiological findings, but entirely different in aetiology, pathogenesis, treatment, and outcomes. Our study aimed to evaluate the clinical and laboratory features which could discriminate the CNO and TBO. The study included 124 patients-91 with CNO and 33 with TBO. All patients underwent routine blood tests: WBC, platelets, ESR, C-reactive protein, haemoglobin, and imaging. The ability of each variable to discriminate CNO from TBO was evaluated with sensitivity and specificity analysis, AUC-ROC analysis, and calculating the odds ratio. Patients with TBO had less number of bone foci (p = 0.0000001), onset age (p = 0.00001), rarely articular involvement (p = 0.01), lower haemoglobin level (p = 0.02), higher incidence of TBO in the male subjects (p = 0.002), and higher leukocyte bands (p = 0.0000001). TBO is rarely characterized by spine (p = 0.0009), foot (p = 0.01), and clavicula (p = 0.047) involvement. The diagnostic rule: criteria allowing to differentiate NBO from TBO are negative bone microbiota tests (sensitivity-100.0%, specificity-100.0%) or major discriminative criteria or clavicula involvement alone (sensitivity-11.0%, specificity-100.0%) and at least four from the five additional criteria: number of foci > 1.0 (p = 0.00002), WBC ≤ 11.0 (p = 0.004), neutrophil bands ≤ 120.0 × 106/l (p = 0.002), lymphocytes ≤ 52% (p = 0.0005), and CRP > 0.2 mg/l (p = 0.003). All patients with monofocal CNO required bone biopsy with microbiology assessment. The created provisional criteria may help to discriminate TBO and CNO and should be used only with other known diagnostic tools. Key Points • Nonbacterial osteomyelitis and tuberculous osteomyelitis are both primarily chronic inflammatory bone diseases with similar presentations. • Nonbacterial osteomyelitis and tuberculous osteomyelitis may be associated with other immune-mediated diseases. • Only bone biopsy can confirm and discriminate both conditions. All patients with monofocal CNO required bone biopsy with microbiology assessment.