The Value of Histology in the Diagnosis of Tuberculous Spondylodiscitis

Background Tuberculous spondylodiscitis (TS) is the most common form of musculoskeletal tuberculosis. Currently, histology is widely used to distinguish tuberculous from nontuberculous disease. Objectives The aim of the present study was to assess the accuracy of histology compared with bacteriology in the diagnosis of TS. Methods This is a single-center case series carried out from January 2014 to February 2018 in a pathology department. It included 121 discovertebral biopsies of infective spondylodiscitis. The measures of diagnostic accuracy of histology were determined taking bacteriology as criterion standard. Results Among the 121 cases, 55 (45.4%) were diagnosed as TS by histological and/or bacteriological findings, 17 (30.9%) were classified as definite TS by bacteriology, and the remaining 38 (69.1%) had positive histology and negative bacteriology. There were 2 false-negatives, which histologically displayed suppuration without granuloma, and 3 false-positives; in one case, histology displayed granulomas without necrosis and culture isolated Brucella. In the 2 others, histology revealed granulomas with caseous-like necrosis and microbiology isolated fungal species. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of histology in the diagnosis of TS were 88.2%, 93.4%, 83.3%, 95.5%, and 92%, respectively. Conclusions Histology is proved to be an accurate diagnostic tool in TS. Suppurative forms of TS without granuloma are rare and represent the main cause of false-negative histology. Suggestive histology of TS does not rule out fungal and brucellar spondylodiscitis. Caseous necrosis is not pathognomonic of tuberculosis. Fungal infection can also exhibit such type of necrosis.