Evaluation of the role of traditional histopathology and Xpert MTB/RIF assay in the diagnosis of spinal tuberculosis

English Keywords:Spinal tuberculosis  Diagnosis  Histopathology  Xpert MTB/RIF

English Abstract:

  【Abstract】 Objectives: To evaluate the role of traditional histopathology(pathology) and Xpert MTB/RIF (Xpert) in the diagnosis of spinal tuberculosis(TB). Methods: We retrospectively analyzed the data of 442 patients clinically diagnosed with spinal TB in Beijing Chest Hospital affiliated to Capital Medical University from January 2015 to April 2018. Among the 442 patients, 227(51.4%) were male and 215(48.6%) were female; aged 18-86 years(46.3±18.0 years old). There were 165 cases of thoracic TB, 162 cases of lumbar TB, 53 cases of lumbosacral TB, 46 cases of thoracolumbar TB, 11 cases of cervical TB, and 5 cases of cervical-thoracic TB. For all patients, pus, sequestrum, granulation tissue and caseous necrotic tissue in the focus were obtained through puncture or surgery, and traditional histopathological examination and Xpert examination were performed to calculate the positive and negative rates of both methods. Histopathological diagnosis was classified into four categories, the first and second categories were confirmed TB, and the third and fourth categories were undiagnosed TB. With histopathological diagnosis as the gold standard, the sensitivity and specificity of Xpert were obtained, and the kappa value was calculated to evaluate the consistency rate of the two methods. Taking histopathological diagnosis as the gold standard, the receiver operating characteristic (ROC) curve of Xpert was drawn and the area under curve(AUC) was calculated to assess the value of Xpert assay. Results: Out of the 442 patients, 292 were diagnosed with confirmed TB by histopathology (66.1%, 95%CI: 61.4%-70.5%), and 150 were undiagnosed TB by histopathology(33.9%, 95%CI: 29.5%-38.6%). The Xpert was positive in 363 cases(82.1%, 95%CI: 78.2%-85.6%), and negative in 79 cases(17.9%, 95%CI: 14.4%-21.8%), and rpoB mutations were found in 43 cases(9.7%). The positive rate of Xpert was higher than that of histopathology(χ2=46.2477, P<0.001). Keeping histopathological diagnosis as the gold standard, of the 292 cases diagnosed to be confirmed TB by histopathology, Xpert was positive in 273 cases and negative in 19 cases; while among the 150 cases of undiagnosed TB by pathology, Xpert was positive in 90 cases and negative in 60 cases. The sensitivity and specificity of Xpert were 93.5%(273/292) and 40%(60/150) respectively. The Kappa value of spinal TB diagnosed by histopathology and Xpert was 0.378(95%CI: 0.290-0.466), indicating poor consistency. The AUC of Xpert was 0.667. The positive rate of joint diagnosis of spinal tuberculosis by histopathological examination and Xpert assay was 86.4%(382/442). Conclusions: Xpert can improve the diagnosis rate of spinal tuberculosis and detect rifampicin-resistant mutations. It is recommended to perform both histopathology examination and Xpert assay when the amount of sample is sufficient.