Comparison of PCR-fluorescence probe and Xpert MTB/RIF in diagnosis of tuberculosis from non-respiratory specimens

Objective To compare the application of PCR-fluorescence probe, Bactec MGIT960 and Xpert MTB/RIF in diagnosis of tuberculosis from non-respiratory specimens. Methods Non-respiratory specimens from 225 patients with suspected tuberculosis admitted in Zhejiang Hospital of Integrated Chinese Medicine and Western Medicine from October 2017 to August 2018 were collected. There were 177 cases of tuberculosis and 48 cases of non-tuberculosis confirmed by clinical diagnosis. All specimens were tested with PCR-fluorescence probe, Xpert MTB/RIF and Bactec MGIT960. The clinical diagnostic results were used as the gold standard, and the receiver operating characteristic curve (ROC) was drawn to evaluate the diagnostic values of three methods. The consistency of PCR-fluorescence probe method with Xpert MTB/RIF assay was analyzed. Results The sensitivity of PCR-fluorescent probe, Xpert MTB/RIF and Bactec MGIT960 in diagnosis of tuberculosis was 53.67% (95/177), 58.76% (104/177) and 31.07% (55/177), respectively. The sensitivity of PCR-fluorescent probe and Xpert MTB/RIF was higher than that of Bactec MGIT 960 culture (χ2=17.60 and 27.41, P 0.05). The specificity of three methods were 100.00% (48/48), 100.00% (48/48) and 97.92% (47/48), respectively (F=1.83, P>0.05). ROC curve analysis showed that the area under the ROC curve (AUC) of PCR-fluorescent probe, Xpert MTB/RIF, and Bactec MGIT960 was 0.768, 0.794, and 0.645, respectively. The diagnostic value of PCR-fluorescent probe and Xpert MTB/RIF for tuberculosis was significantly higher than that of Bactec MGIT960 (Z=5.19 and 6.52, P 0.05). The PCR-fluorescent probe and Xpert MTB/RIF had a good consistency (kappa=0.829). Conclusion Xpert MTB/RIF is superior to PCR-fluorescence probe in the detection of tuberculosis in non-respiratory specimens such as tissues and pus, but the two have good consistency. The PCR-fluorescence probe method is economical and practical, and easy to promote, which has a high clinical application prospects. Key words: Tuberculosis; Diagnosis; Non-respiratory specimens; PCR-fluorescence probes; Xpert MTB/RIF