Whole-body PET/CT reveals systemic dissemination in spinal tuberculosis: findings from the Spinal TB X cohort

INTRODUCTION: Spinal tuberculosis (STB) is a severe form of extrapulmonary tuberculosis associated with diagnostic delay and substantial morbidity. The extent of disease-isolated versus disseminated STB-remains poorly defined. We applied whole-body 18F-FDG-PET/CT to characterise the clinical and radiographic phenotype of STB. MATERIAL AND METHODS: The Spinal TB X cohort (NCT05610098) is a prospective study of HIV-infected and uninfected patients with suspected STB in Cape Town, South Africa. We analysed the first ten patients with microbiologically confirmed STB. Demographic, clinical, microbiological, histological, and PET/CT data were collected. Isolated STB was defined as spinal involvement only, while disseminated STB was defined as additional organ involvement confirmed by microbiology and/or PET/CT. The study was approved by the Human Research Ethics Committee of the University of Cape Town (HREC 243/2022). Written informed consent was obtained from all participants. RESULTS: Ten patients (median age 44 years [IQR 26], 80% male, 30% HIV-positive) were included. A total of 14 spinal lesions involving 44 vertebrae were detected; psoas abscesses were present in six patients. Mean SUVmax and SUVmean of spinal lesions were 15.2 (SD 4.6) and 6.9 (SD 1.5), respectively; mean total lesion glycolysis (TLG) was 363.2 SUVbw*mL (SD 341.9). Based on microbiology alone, 40% had disseminated STB, combining microbiology with PET/CT findings, 60% had disseminated disease. CONCLUSION: Whole-body PET/CT revealed a high frequency of disseminated disease, underscoring the systemic nature of TB even when clinical presentation is spinal. Isolated STB may represent a distinct phenotype. PET/CT shows promise for assessing disease burden and warrants further evaluation.