Cytopathological and Bacteriological Diagnostic Performance of GeneXpert in Clinically Suspected Tuberculous Lymphadenitis in a Tertiary Care Hospital, Bihar (India)

Author(s): Imtiaz Ahmad1 , Rajiv Kumar2 , Chandan Kumar Poddar3 , S. K. Shahi4

BACKGROUND Tuberculosis is a prehistoric disease and confirmation of its existence was seen in the Vedas. The oldest of them (Rigveda, 1500 BC) calls the infection yaksma. It claimed millions of lives in Europe and was called `The White Plague’. Robert Koch has written that tuberculosis killed one third of Europeans of middle age. METHODS This is a descriptive study. Tuberculous lymphadenitis isolates from sputum samples of clinically suspected cases of tuberculosis seen in Vardhman Institute of Medical Sciences, Pawapuri, Nalanda, Bihar and Associated Hospital of Bihar between March 2019 and March 2020 were included in the study. The study protocol was approved by the hospital ethics committee. RESULTS A total of 200 fine-needle aspirated specimens from lymph nodes were integrated in the study. Out of 200 cases, 90 aspirates were reported as cytomorphology suggestive of tuberculous lymphadenitis. Compared to the reference standard, Xpert MTB/RIF correctly identified 88 out of 90 TB cases (sensitivity, 97.80%). The possible false-negative result had a prolonged transit interval of 9 days before Xpert MTB/ RIF testing, which may have affected the result. Xpert MTB/ RIF was positive in two cases, with negative cytomorphology and culture (specificity, 95.65%). The cytomorphology from one of the false-positive results showed a necrotizing suppurative lymphadenitis, which is consistent with TB. However, no organisms could be identified on microscopy or culture. The cytomorphology of the other false positive result showed an epithelial inclusion cyst, and the reason for this false-positive result remains unknown. CONCLUSIONS FNAB is a simple procedure which can be performed in an outpatient setting by clinicians or nursing staff after a short training period (21, 22). It is ideal for use in resource-limited settings, including more remote and rural areas (22). Specimen collection is simple and safe. With the use of a transport vial, virtually no sample preparation is required and there is minimal risk of contamination. Furthermore, the transmission risk to the operator may also be reduced. Combining FNAB and rapid genotypic diagnosis using automated systems should greatly improve access to appropriate diagnosis and treatment for patients with tuberculous lymphadenitis.