Diagnostic method in TB is all except –
Correct Answer: Biopsy
Description: Active tuberculosis Diagnosing active tuberculosis based only on signs and symptoms is difficult,as is diagnosing the disease in those who have a weakened immune system.A diagnosis of TB should, however, be considered in those with signs of lung disease or constitutional symptoms lasting longer than two weeks. A chest X-ray and multiple sputum cultures for acid-fast bacilli are typically pa of the initial evaluation.[Interferon-g release assays and tuberculin skin tests are of little use in the developing worldInterferon gamma release assays (IGRA) have similar limitations in those with HIV. A definitive diagnosis of TB is made by identifying M. tuberculosis in a clinical sample (e.g., sputum, pus, or a tissue biopsy). However, the difficult culture process for this slow-growing organism can take two to six weeks for blood or sputum culture. Thus, treatment is often begun before cultures are confirmed. Nucleic acid amplification tests and adenosine deaminase testing may allow rapid diagnosis of TB. These tests, however, are not routinely recommended, as they rarely alter how a person is treated. Blood tests to detect antibodies are not specific or sensitive, so they are not recommended Latent TB The Mantoux tuberculin skin test is often used to screen people at high risk for TB.Those who have been previously immunized with the Bacille Calmette-Guerin vaccine may have a false-positive test result.The test may be falsely negative in those with sarcoidosis, Hodgkin's lymphoma, malnutrition, and most notably, active tuberculosis.Interferon gamma release assays, on a blood sample, are recommended in those who are positive to the Mantoux test.These are not affected by immunization or most environmental mycobacteria, so they generate fewer false-positive results.However, they are affected by M. szulgai, M. marinum, and M. kansasii.IGRAs may increase sensitivity when used in addition to the skin test, but may be less sensitive than the skin test when used alone Ref Harrison20th edition pg 1019
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