Diagnostic Utility of GeneXpert MTB/RIF Assay in EPTB Detection in Formalin Fixed Paraffin Embedded Tissue Biopsies in South Western Uganda

Abstract

Purpose: Formalin-fixed tissue biopsies submitted to the Histopathology Laboratory were explored for possible use in the GeneXpert MTB/Rifampicin assay for EPTB diagnosis, therefore this study aimed to determine the diagnostic utility of the GeneXpert MTB/RIF assay in EPTB detection in formalin-fixed paraffin-embedded tissue biopsies using Ziehl-Neelsen (ZN) and Haematoxylin and Eosin (H&E) staining as a composite reference standard. Methods: A total of 89 selected archived formalin-fixed paraffin-embedded tissues with histological features of tuberculosis were included in the study. ZN and H&E staining were performed as a composite reference standard, followed by GeneXpert MTB/RIF assay as diagnostic test. Data were analysed using STATA software version 17.0. Results: Of the 89 specimens enrolled, 55% were male. The Lymph node was the commonest site (64%). 15/89 (16.9%) cases were positive for ZN, 45/89 (50.6%) were positive for H&E and 27/89 (30.3%) were positive for GeneXpert. The overall sensitivity and specificity of GeneXpert were 48.94% (95% CI: 38.55%–59.32%) and 90.48% (95% CI: 84.38%–96.57%), respectively, in lymph node tissues, were 52.94% (95% CI: 39.98%–65.90%) and 82.61% (95% CI: 72.77%–92.45%), respectively, and in Non-Lymph node tissues, were 38.46% (95% CI: 21.61%–55.32%) and 100% (95% CI: 100%–100%), respectively. Conclusion: The GeneXpert MTB/RIF assay is a potential tool for diagnosing EPTB in FFPE tissues and may be used in the development of an algorithm in the histopathology laboratory.