Role of cartridge-based nucleic acid amplification test in diagnosis of extrapulmonary tuberculosis; a cross-sectional study.

Abstract

Background:

Tuberculosis (TB) is an infectious disease caused by an acid fast bacilli known as Mycobacterium tuberculosis. It primarily affects the lungs (Pulmonary TB) but can also affect other organs (EPTB) like lymph nodes, pleura, CNS, meninges, bones and joints, kidney, spine, etc, which remains a major public health problem.

Methodology:

Patients with presumptive extrapulmonary TB, presenting complaints, Comorbidities, HIV status, and any past & contact history of tuberculosis were noted.  Investigations like CPB, ESR, HIV, and RBS were done in all cases. For patients with suspected TB lymphadenopathy, FNAC was done, and pus was obtained and sent for CBNAAT & culture. Patients with pleural TB & Other EPTB samples, like pleural fluid, CSF, and ascitic fluid aspirated and sent for ADA proteins, cytology, and CBNAAT & culture. 

Results:

Out of 100 extra-pulmonary cases, 55% were males and 45% were females. The most common age group was 21-40 years.  The most common EPTB found was lymph node TB (45%), followed by TB pleural effusion (30%) and abdominal TB (10%). Sensitivity and Specificity of CBNAAT were 62.2% and 74.50%, respectively, in comparison with Culture. Out of the 100 samples, CBNAAT was Positive in 42 samples, culture was positive in 45, of which 9(21.42%) were Rifampicin-resistant.

Conclusion:

The diagnostic yield of CBNAAT was 42% in the EPTB samples. Therefore, the present study concludes that CBNAAT definitely plays a crucial role in the diagnosis of EPTB because of its simplicity and rapid turnaround time of 2 hrs & detects Rifampicin Resistance simultaneously for early initiation of MDR TB treatment compared to culture, as it takes a longer duration. 

Recommendation:

CBNAAT is recommended as the initial test for suspected extrapulmonary tuberculosis, providing rapid detection of TB and rifampicin resistance.