Patterns of Extrapulmonary Tuberculosis Using CBNAAT: A Retrospective Study

Background: Extra-pulmonary tuberculosis is a milder form of the disease in terms of infectivity as compared to pulmonary tuberculosis. Diagnosis of Extra-pulmonary TB (EPTB) is a challenge.

Aim: The study seeks to assess the sites of extra-pulmonary involvement during 2013-2017 in a tertiary care hospital cum medical college. The study also wanted to evaluate the role of the Cartridge Based Nucleic Acid Amplification Test (CBNAAT) in the diagnosis of EPTB and compare its efficacy with AFB Culture.

Methods: A total of 470 EPTB cases were diagnosed between 2013 and 2017 from 840 TB treatment records maintained in designated microscopy centre. Specific samples from appropriate sites were taken up for smear for AFB, CBNAAT and AFB culture. The sensitivity and specificity of CB NAAT were also computed. All the analysis was carried out using standard statistically significant STATA 15.1.

Results: There was incremental detection and registration in both TB and EPTB cases from 96 and 50 cases in 2013 to 246 and 150 cases in 2017 respectively. Among the total 470 EPTB cases in 2013-2017 (55.9%), lymph nodes followed by pleura and abdomen were the organs having maximum involvement. Bone involvement was more witnessed in adult males than children (p <0.05). There was male preponderance. CBNAAT results were 100 % sensitive and 87.5% specific. Lymph node samples and pus elsewhere in the body had much better diagnostic yield than serous effusions. The number of patients diagnosed from 2013 revealed a steady increase in numbers till 2017; this is due to improved awareness among the clinicians and availability of new diagnostic modalities in the extrapulmonary presentations and awareness to register in RNTCP services for availing the services.

Conclusions: EPTB needs a high index of suspicion and judicious invasive diagnostic tests. Awareness and availability of diagnostic services in tertiary care institutions have led to increased reporting of EPTB under RNTCP services. CBNAAT can also be utilized as a point of care testing for lymph node aspirate and pus specimens.