The Application of Xpert Mycobacterium tuberculosis/Rifampicin, Quantitative Polymerase Chain Reaction and High Resolution Melting Curve in the Diagnosis of Superficial Lymph Node TB

Abstract

Objective: The diagnostic sensitivity and specificity of conventional methods for superficial lymph node tuberculosis (LNTB) are not ideal. We evaluated several novel methods including Xpert Mycobacterium tuberculosis/rifampicin (Xpert MTB/RIF) technology, quantitative fluorescence Polymerase Chain Reaction (qPCR) and High-Resolution Melting Curve (HRMC) in the diagnosis of superficial lymph node TB.

Methods: Specimens from eighty-one consecutive patients with suspected LNTB and thirteen cases with other lymph node disease were analyzed by Xpert MTB/RIF, qPCR, and HRMC.

Results: Among 81 patients with clinical suspicion of LNTB, there were 74 (91.4%) cases positive Mycobacterium tuberculosis Complex (MTBC) of Xpert MTB/RIF, 60 (74%) positive of qPCR, 24 (29.6%) of positive of BACTEC MGIT960 culture, and 13 (16%) cases positive of Roche culture. 38 cases (46.9%) were diagnosed with LNTB. All test methods showed a diagnostic specificity of 100% for LNTB. The sensitivity of molecular biology techniques was significantly higher than that of the traditional diagnostic methods, and Xpert MTB/RIF was the most sensitive diagnostic assay. On Rifampinresistant detection, Xpert MTB/RIF detected three cases (3.7%) with rpoB gene mutation, and Mycobacterium tuberculosis susceptibility testing detected 2 rifampicin-resistant cases (2.4%) which were consistent with Xpert MTB/RIF results. In the Isoniazid-resistant, 7 cases (8.1) of isoniazid resistance mutations (8.1%) were detected by HNC and 1 case was confirmed by Isoniazid susceptibility test.

Conclusion: Molecular detection increased the diagnostic sensitivity of LNTB and improved the detection sensitivity for rifampin and isoniazid resistance strain.

Keywords: High-Resolution Melting Curve (HRMC); Lymph node TB; Rifampin; Xpert MTB/RIF; isoniazid; resistance..