Related Experiment Video
Updated: Jul 7, 2026

Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
Low cost in-house PCR for the routine diagnosis of extra-pulmonary tuberculosis
D Magana-Arachchi1, J Perera, S Gamage
1Department of Microbiology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka. nayomam@yahoo.com
Setting:
Conventional methods for the identification of mycobacteria are slow and labour intensive. DNA amplification methods offer rapid sensitive and specific diagnosis.
Objective:
To determine the feasibility of an in-house polymerase chain reaction (PCR) method to detect Mycobacterium tuberculosis in clinical samples.
Design:
The present study focused mainly on diagnosing extra-pulmonary tuberculosis (EPTB) using an in-house PCR method in 465 clinical samples. This study also compared the efficacy of a standard phenol-chloroform (PC) extraction procedure and the guanidine thiocyanate with diatomaceous silica (GTCS) method of DNA extraction and purification. A subsample of patients was used for the validation of results based on the final diagnosis.
Results:
Among 373 patients with suspected EPTB, 75 specimens were positive by PCR, four by microscopy and six by culture. Of the 25 PCR-positive patients, 95% had a final diagnosis of TB. Globally, the GTCS method was found to be superior to the PC method for DNA extraction and removal of inhibitors from clinical specimens.
Conclusion:
The DNA amplification method was found to be significantly more sensitive and rapid compared to culture and microscopy for a reliable final diagnosis of EPTB.
Related Concept Videos
Pulmonary Tuberculosis IV
Several diagnostic approaches are used to detect TB. The conventional method is the Tuberculin Skin Test (TST), also known as the Mantoux test. However, this method has...
Pulmonary Tuberculosis V
Latent tuberculosis infection occurs when TB bacteria are present in a person's body, but are not causing illness or symptoms. It is not contagious, and preventive treatment is crucial to avoid the progression...
Pulmonary Tuberculosis I
Causative Organism
The primary infectious agent causing tuberculosis is Mycobacterium tuberculosis, a slow-growing, acid-fast, aerobic rod that exhibits sensitivity to heat and ultraviolet light. Instances of Mycobacterium bovis and Mycobacterium avium contributing to the development of TB infection are rare.
Mode of...
Pulmonary Tuberculosis III
The first classification is based on the development of the disease, and it includes the following categories:
Pulmonary Tuberculosis II
Here is a detailed explanation of its pathophysiology:
Transmission: The process begins when a person inhales droplet nuclei containing M. tuberculosis. These are typically released into the air when an individual with pulmonary or...
