Role of GeneXpert MTB/RIF assay for the diagnosis of cervical lymph node tuberculosis and rifampicin resistance

Objectives: Tuberculosis (TB) of lymph node (TB lymphadenitis) is one of the most common forms of extrapulmonary TB (EPTB) whose diagnosis is critically challenging. Although new diagnostic methods have been developed, especially in patients without a history of TB, the cervical tuberculous lymphadenitis diagnosis is still elusive. This study assessed the applicability of GeneXpert in early diagnosis of EPTB, especially cervical lymphadenopathy. Materials and Methods: The study was conducted in a tertiary care hospital from January 2018 to December 2020 at the department of microbiology. All the samples of cervical lymph node tissue and lymph node aspirate were followed as per the routine protocol for mycobacterial identification. The sample was divided into two parts: one was used for the new molecular-based GeneXpert MTB/RIF assay and the second one was tested by direct and concentrated acid-fast bacilli microscopy by Z-N staining and culture for the detection of MTB. Results: Among the 145 samples tested, the GeneXpert detected the DNA of MTB in 89 samples (61.37%), whereas the culture test was positive in 42 (28.93%) specimens. GeneXpert also detected 7 rifampicin resistance cases. GeneXpert sensitivity and specificity results were assessed according to culture results. The sensitivity and specificity of the GeneXpert assay were 85.71% and 48.54%, respectively. Conclusion: GeneXpert MTB/RIF should be used in conjunction with clinical presentation and other molecular investigation in nonrespiratory specimens.