Abstract :
Introduction: Tuberculosis (TB) is an important health problem in the developing countries.
Extrapulmonary sites of TB commonly include lymph nodes, pleura, gastrointestinal system, genitourinary
system, central nervous system, bones. Most of the EPTB cases present with lymphadenopathy and
effusion. The conventional methods to diagnose EPTB includes fine needle aspiration cytology (FNAC)
and demonstration of acid fast bacilli (AFB) using Zeihl- Neelson (ZN) staining.
Objectives: 1). To assess the efficacy of FNAC positivity in comparison to CB-NAAT in the diagnosis of
EPTB. 2). To assess the efficacy of AFB positivity in comparison to CB-NAAT in the diagnosis of EPTB.
Materials and Methods: The present retrospective record based study was conducted at the Department
of Pathology and CB-NAAT Centre, Mandya Institute of Medical Sciences (MIMS), Mandya, Karnataka.
The study was started after obtaining approval from the Institutional Ethics Committee.
The records of suspected 100 EPTB patients who had under gone FNAC, ZN stain and CB-NAAT test for
EPTB diagnosis during the study period of four months from March to June 2018 were analysed.
Results: A total of 100 subjects were included in the final analysis. In our study, youngest patient was
8 months and oldest was 75 years. Of the 100 cases, lymph node involvement accounted for 96 cases
and soft tissue swellings accounted for 4 cases. The diagnosis of FNAC of 100 cases were reactive
lymphoid hyperplasia, suppurative lesion, epithelioid granuloma without necrosis, epithelioid granuloma
with necrosis, caseous necrosis without epithelioid cells and lymphoma and their proportion were 30%,
21%, 22%, 13%, 12% and 2% respectively. Out of 47 cases with FNAC findings favouring EPTB, 30
were CB-NAAT positive and 17 were CB-NAAT negative. Out of 53 cases with negative FNA findings,
CB-NAAT was positive in 5 cases (14.2%). Only 13 cases were positive for AFB when compared to 30
CB-NAAT positive cases. Among the 35 CB-NAAT positive cases, 13 (37.1%) cases were AFB positive.
Conclusion: CB-NAAT is a rapid, simple test for early diagnosis of EPTB because of high specificity and
PPV. It can also detect the cases missed by FNAC and ZN techniques.
Keyword :
Gene Xpert, Xpert MTB/RIF assay, Zeihl-Neelson staining.