Extra pulmonary tuberculosis: a diagnostic dilemma

Area of Science:

• Microbiology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Tuberculosis (TB) is a significant global health issue, with India as a high-burden country.
• Mycobacterium tuberculosis is the primary cause, but Mycobacterium bovis is an emerging pathogen in developing nations.
• Extra-pulmonary tuberculosis (EPTB) constitutes approximately 20% of all TB cases and presents diagnostic challenges due to paucibacillary samples and lengthy conventional methods.

Purpose of the Study:

• To evaluate the efficacy of a rapid molecular method for diagnosing extrapulmonary tuberculosis (EPTB).
• To differentiate between Mycobacterium tuberculosis and Mycobacterium bovis infections in EPTB cases.
• To assess the diagnostic accuracy of a two-step PCR targeting the hupB gene for EPTB.

Main Methods:

• A prospective study involving 300 suspected EPTB patients over five years.
• Analysis of cerebrospinal fluid, ascitic fluid, and lymph node fine needle aspirates.
• A two-step PCR assay targeting the hupB gene was employed, with clinical response to anti-tubercular therapy (ATT) serving as the gold standard.

Main Results:

• The hupB gene PCR showed a sensitivity of 90.32% and specificity of 94.48%.
• Out of 155 ATT responders, 147 samples tested positive via PCR.
• Identified infections included 85.71% M. tuberculosis, 9.52% M. bovis, and 4.76% co-infections.

Conclusions:

• The hupB gene PCR is a sensitive and specific molecular tool for rapid EPTB diagnosis.
• This method aids in differentiating between M. tuberculosis and M. bovis, crucial for targeted treatment.
• The study highlights the potential of molecular diagnostics to overcome limitations in conventional EPTB detection.