Improving diagnosis of tuberculous lymphadenitis by combination of cytomorphology and MPT64 immunostaining on cell blocks from the fine needle aspirates

Abstract

Background Extra pulmonary tuberculosis (EPTB) constitutes 18% of all tuberculosis (TB) cases and tuberculous lymphadenitis (TBL) constitutes 20–40% of EPTB. Diagnosis of TBL is challenging because of the paucibacillary nature of the disease. Objective To investigate the diagnostic potential of a new antigen detection test based on the detection of M. tuberculosis complex specific antigen MPT64 from fine needle aspirate (FNA) cytology smears and biopsies obtained from patients with clinically suspected TBL using immunohistochemistry (IHC). Materials and methods This study was conducted at Khyber Teaching Hospital and Rehman Medical Institute, Peshawar, Pakistan, from January 2018 to April 2019. Samples, including FNA (n = 100) and biopsies (n = 8), were collected from 100 patients with presumptive TBL. Direct smears and cell blocks were prepared from the FNA samples. All samples were subjected to hematoxylin–eosin (H&E) staining, Ziehl-Neelsen (ZN) staining, and immunostaining with polyclonal anti-MPT64 antibody. The culture was performed only for biopsy specimens. All patients were followed until the completion of anti-TB treatment. The response to treatment was included in the composite reference standard (CRS) and used as the gold standard to validate the diagnostic tests. Results The sensitivity, specificity, positive and negative predictive values for ZN staining were 4.4%,100%,100%,56%, for culture were 66%,100%,100%,50%, for cytomorphology were 100%,90.91%,90%,100%, and for immunostaining with anti-MPT64 were all 100%,respectively. The morphology and performance of immunohistochemistry were better with cell blocks than with smears. Conclusion MPT64 antigen detection test performed better than ZN and cytomorphology in diagnosing TBL. This test applied to cell blocks from FNA is robust, simple, and relatively rapid, and improves the diagnosis of TBL.

Diagnostic value of tuberculosis-specific antigens ESAT-6 and CFP10 in lymph node tuberculosis

“…Characteristically, granulomatous inflammation, with or without caseous necrosis, is identified, yet such patterns are not exclusive to tuberculosis and may also manifest in conditions such as non-tuberculous mycobacterial disease [ 14 ], fungal infections [ 15 ], leprosy [ 16 ], sarcoidosis [ 17 ], and foreign body granuloma [ 18 ], among others. Thus, integrating pathological findings with mycobacterial etiology is pivotal for enhanced diagnostic precision.Acid-fast staining is a conventional method for pathogen detection in laboratory settings, albeit with a variable positive rate of 0%–34.4% as documented in literature [ 7 , 9 , 19 ]. This study corroborates these findings, demonstrating a 12.3% positive rate (9/72) for acid-fast staining, aligning with previous research.…”

“…Furthermore, the 2023 consensus on diagnosing superficial lymph node tuberculosis suggests that positive MTB antigen tests can assist in diagnosis [ 5 ]. Despite the focus on antigens such as MPT64, 38 kDa, ESAT-6, Ag85, and BCG components [ [6] , [7] , [8] , [9] ], a search for which yielded a total of 35 articles from specific databases, there is still a notable lack of IHC-specific antibodies and standardized interpretive criteria for clinical use, underscoring the need for further translational research [ 4 ].…”