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Principles and Methods of Testing for TB diagnosis
Learning ObjectivesThe learner will be able to list and discuss acceptable tests for TB diagnosis as per algorithms under NTEP.
National Tuberculosis Elimination Programme (NTEP) strives for all presumptive TB patients to be microbiologically confirmed. Under NTEP, the acceptable methods for microbiological diagnosis of TB are:
Sputum Smear Microscopy (for Acid Fast Bacilli - AFB): Sputum Smear microscopy is the primary tool which is reliable, inexpensive, easily accessible and rapid method of diagnosing PTB, where in the bacilli are demonstrated in the sputum. Two types:
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Ziehl-Neelsen Staining
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Fluorescence staining
Rapid diagnostic molecular test: Rapid molecular tests that use techniques like NAAT are very specific. They amplify the genomic material in the patient sample and hence enhances detection
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Nucleic Acid Amplification Test (NAAT) e.g., GeneXpert, TrueNat
Figure: Genxpert Machine for CBNAAT
Figure: Truenat Machine
- Line Probe Assay
Culture and DST: A culture test involves studying bacteria by growing the bacteria on different substances. This is to find out if particular bacteria are present. In the case of the TB culture test, the test is to see if the TB bacteria Mycobacterium tuberculosis, are present.
Two types:
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Solid (Lowenstein Jensen) media
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Liquid media (Middlebrook) e.g., Bactec MGIT etc.
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Content Revised
drharshshah Fri, 10/03/2023 - 11:40
I have entirely updated the section with images. Kindly review it and modify accordingly.