Cartridge based nucleic acid amplification test: a sensitive diagnostic tool for tuberculosis on fine needle aspirates samples

Abstract

Background: The extrapulmonary tuberculosis (EPTB) is challenging to diagnose due to its pauci-bacillary nature. According to recent research, WHO recommends cartridge based nucleic acid amplification test (CBNAAT) to be used as initial diagnostic test in suspected cases of extrapulmonary tuberculosis. Aim of the present study is to assess the role of CBNAAT in comparison with cytomorphological features upon fine needle aspiration cytology (FNAC) and Ziehl-Neelson (ZN) stain in clinically suspected cases of EPTB.Methods: Present pilot study is descriptive cross-sectional study of 439 cases of clinically suspected EPTB over a period of 12 months (January 2019 to December 2019). After procedure of fine needle aspirates, smears were stained with routine H&E, papanicolaou stain and ZN stain. In the same setting, aspirate was also sent for CBNAAT. Results were obtained after detailed study.Results: Out of 439 cases, presumptive tuberculosis was diagnosed in 192 cases showing either epithelioid cell granulomas or caseous necrosis or both upon morphology, while overall 94 cases were positive on ZN stain and 146 cases were CBNAAT positive with the sensitivity of 84.04% and specificity of 80.57%.Conclusions: FNAC is the cheapest and simplest method to diagnose extrapulmonary tuberculosis, however those smears where tuberculosis cannot be diagnosed on FNAC like suppurative lesions, reactive lymphadenitis and low cellularity, CBNAAT plays a key role for the correct diagnosis thereby significantly reducing the morbidity and mortality.

Cervical tuberculous lymphadenitis

“…Our study included 100 clinically suspected cases of cervical tuberculous lymphadenitis. Maximum number of patients (70%) were in age group of 11-30 years, which was similar to study conducted by Patil SB et al [7] where majority of patients (53%) were in this age group, also in Tadesse. M et al [8] maximum no of patients (58%) were in 16-30 years age group and Swati Nair et al [9] reported 59% cases in the age group of 11-30 years.…”

“…Our study showed female predominance which was similar to Patil SB et al [7], Tadesse M et al [8] and Gautam et al [10], but in contrast to Swati Nair et al [9] which reported male to female ratio 1.27:1. In our study most of patients(70%) did not have constitutional symptoms which is similar to Jha et al (12) and contrast to Dandapat et al [13].…”

Extra pulmonary tuberculosis manifestation in head and neck and its diagnosis with recent tools like cartridge based nucleic acid amplification test

“…5 Patil et al noted the sensitivity of CBNAAT to be similar to the present study, but specificity was much higher in the reference study (80.57%) as compared to the present study (50%). 25 Sensitivity, specificity, positive predictive value, and negative predictive value of CBNAAT were documented to be 92.7%, 98.9%, 97.1%, and 97.2% respectively in a study by Kumar et al 26…”