Diagnostic Approach to Extrapulmonary Tuberculosis by Cartridge-based Nucleic Acid Amplification Test

Area of Science:

• Medical Diagnostics
• Infectious Diseases
• Molecular Biology

Background:

• Tuberculosis (TB) remains a global health challenge, with extrapulmonary TB (EPTB) posing diagnostic difficulties due to varied presentations and low bacterial load.
• Early and accurate diagnosis of EPTB is crucial for effective patient management and disease control.
• The Cartridge-based nucleic acid amplification test (CBNAAT) offers a rapid and sensitive method for TB detection.

Purpose of the Study:

• To evaluate the diagnostic utility of CBNAAT for the early detection of extrapulmonary tuberculosis (EPTB).
• To compare the performance of CBNAAT against conventional smear microscopy in diagnosing EPTB.
• To assess the identification of rifampicin resistance using CBNAAT in EPTB cases.

Main Methods:

• A comparative study was conducted over 8 months in a rural tertiary care hospital.
• Samples from various sites (pleural fluid, lymph nodes, CSF, etc.) were tested using both CBNAAT and fluorescent smear microscopy.
• Positive samples underwent culture for further analysis and comparison.

Main Results:

• Out of 593 samples, CBNAAT detected 52 positive EPTB cases, including six with rifampicin resistance.
• Fluorescent smear microscopy identified only 33 positive samples, highlighting its limitations in EPTB diagnosis.
• CBNAAT demonstrated superior sensitivity in detecting acid-fast bacilli compared to smear microscopy.

Conclusions:

• CBNAAT is a highly effective tool for the early and accurate diagnosis of extrapulmonary TB.
• The test accurately identifies cases that are false negatives by conventional smear microscopy.
• CBNAAT facilitates prompt initiation of appropriate treatment for EPTB patients.