The most frequent type of musculoskeletal TB is tuberculous spondylodiscitis (TS). Histology is now routinely utilized to differentiate tuberculous from nontuberculous illness. The purpose of this study was to examine the accuracy of histology and bacteriology in the diagnosis of TS. This is a single-center case series that was conducted in a pathology department from January 2014 to February 2018. It contained 121 infective spondylodiscitis vertebral biopsies. The diagnostic accuracy of histology was assessed using bacteriology as the criteria standard. Among the 121 cases, 55 were categorized as TS based on histological and/or bacteriological results, 17 as definite TS based on bacteriology, while the remaining 38 had positive histology but negative bacteriology. There were two false-negatives, with histology showing suppuration but no granuloma, and three false-positives, with histology showing granulomas but no necrosis and culture revealing Brucella. Histology found granulomas with caseous necrosis in the other two cases, and microbiology detected fungus species. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of histology in the diagnosis of TS were 88.2 percent, 93.4 percent, 83.3 percent, 95.5 percent, and 92 percent, respectively.

Histology has been shown to be an accurate diagnostic method in TS. Suppurative types of TS without granuloma are uncommon and are the leading source of false-negative histology. The histology of TS does not rule out fungal or brucellar spondylodiscitis. Caseous necrosis is not a pathognomonic sign of TB. Necrosis of this sort can also be caused by a fungus infection.

Reference:https://journals.lww.com/jclinrheum/Abstract/2020/03000/The_Value_of_Histology_in_the_Diagnosis_of.5.aspx