Authors: Madhukar Pail MD, PhD-Author and Series Editor
Number of pages: 6
Download (2018, pdf, 5.10mb)
Overview: India has the highest burden of tuberculosis (TB) in the world, and every GP will need to consider TB as a differential diagnosis in persons with cough lasting two weeks or more, or with unexplained chronic fever and/or weight loss. Sputum is the most important sample for laboratory testing. Although blood is a popular sample in theIndian privatesector, there is no accurate blood test for active TB. Blood-based antibody tests (e.g., IgG/lgM ELISA orrapid tests) and interferon-gamma release assays (e.g., TB Gold) are not accurate and should not be used for pulmonary TB diagnosis. In fact, the Government of India has recently banned the use of serodiagnostic tests for TB. There are three internationally accepted sputum tests for active TB:sputum smear microscopy for acid-fast bacilli; nucleic acid amplification test(e.g., GeneXpert); and culture. Chest radiography is useful but cannot provide a conclusive diagnosis on its own, and needs to be followed by sputum testing.
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Diagnosis of Pulmonary Tuberculosis: What Every GP Should Know
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Question 1 of 6
1. Question
Which of the following diagnostics tests is intended for latent tuberculosis infection?
Correct
The correct answer is (c). Interferon-gamma release assays (e.g., TB Gold) are meant for the diagnosis of latent TB infection. They should not be used for active TB diagnosis because they cannot distinguish between latent TB and active disease. A 2011 World Health Organization (WHO) policy discourages their use for active TB diagnosis.
Reference: World Health Organization . Policy statement Use of tub erculosis interferon-gamma re lease assays (IGRAs) in lowand middle-income countries. In. Geneva: World Health Organization; 2011.Incorrect
The correct answer is (c). Interferon-gamma release assays (e.g., TB Gold) are meant for the diagnosis of latent TB infection. They should not be used for active TB diagnosis because they cannot distinguish between latent TB and active disease. A 2011 World Health Organization (WHO) policy discourages their use for active TB diagnosis.
Reference: World Health Organization . Policy statement Use of tub erculosis interferon-gamma re lease assays (IGRAs) in lowand middle-income countries. In. Geneva: World Health Organization; 2011. -
Question 2 of 6
2. Question
Which of the following diagnostics tests can be used to diagnose drug resistant tuberculosis?
Correct
The correct answer is (b). Liquid culture can be used to grow Mycobacterium tuberculosis and also identify drug resistance (to first and second line drugs). The use of liquid culture is endorsed by the WHO.
Reference: World Health Organization . The use of liquid medium for culture and DSf. URL: http://www.who.int/tb/laboratory/policy_liquid_medium_foc culture_dst/en/index.html. In. Geneva: World Health Organization; 2007.Incorrect
The correct answer is (b). Liquid culture can be used to grow Mycobacterium tuberculosis and also identify drug resistance (to first and second line drugs). The use of liquid culture is endorsed by the WHO.
Reference: World Health Organization . The use of liquid medium for culture and DSf. URL: http://www.who.int/tb/laboratory/policy_liquid_medium_foc culture_dst/en/index.html. In. Geneva: World Health Organization; 2007. -
Question 3 of 6
3. Question
Which of the following tests are banned by the government of India?
Correct
The correct answer is (d). The Indian Government has banned the use, sale and import of all commercial serological (antibody-detection) TB tests. This includes ELISA as well as rapid antibody tests. The ban applies to domestic as well as imported serodiagnostics kits. The ban is based on a WHO policy that strongly recommends against the use of serological, antibody tests for TB. The International Standards for TB Care also discourages the use of serological TB tests.
References:
World Health Organization. Policy statement Use of tuberculosis interferon-gamma re lease assays (IGRAs) in low and middle-income countries. In. Geneva: World Health Organization; 2011.
World Health Organization. Policy statement Commercial serodiagnostic tests for diagnosis of tuberculosis. In. Geneva: World Health Organization; 2011.Incorrect
The correct answer is (d). The Indian Government has banned the use, sale and import of all commercial serological (antibody-detection) TB tests. This includes ELISA as well as rapid antibody tests. The ban applies to domestic as well as imported serodiagnostics kits. The ban is based on a WHO policy that strongly recommends against the use of serological, antibody tests for TB. The International Standards for TB Care also discourages the use of serological TB tests.
References:
World Health Organization. Policy statement Use of tuberculosis interferon-gamma re lease assays (IGRAs) in low and middle-income countries. In. Geneva: World Health Organization; 2011.
World Health Organization. Policy statement Commercial serodiagnostic tests for diagnosis of tuberculosis. In. Geneva: World Health Organization; 2011. -
Question 4 of 6
4. Question
The ideal clinical specimen for pulmonary TB diagnosis is:
Correct
The correct answer is (b). Sputum is the best clinical specimen for diagnosis of pulmonary TB. There are no accurate, validated tests for specimens such as blood, urine and tissue.
Incorrect
The correct answer is (b). Sputum is the best clinical specimen for diagnosis of pulmonary TB. There are no accurate, validated tests for specimens such as blood, urine and tissue.
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Question 5 of 6
5. Question
Advantages of culture for TB compared to sputum microscopy alone include all of the following EXCEPT:
Correct
The correct answer is (d). Culture is not faster than smear microscopy because even liquid culture needs 10 -14 days for a result to be obtained. Sputum smear results are usually available within 1-2 days.
Incorrect
The correct answer is (d). Culture is not faster than smear microscopy because even liquid culture needs 10 -14 days for a result to be obtained. Sputum smear results are usually available within 1-2 days.
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Question 6 of 6
6. Question
Which of the following statements is FALSE about chest X-rays for TB diagnosis:
Correct
The correct answer is (c). Chest X-rays alone is NOT sufficient to diagnose pulmonary TB) It needs to be followed by sputum testing. While chest X-rays have fairly high sensitivity for pulmonary TB, its specificity is low. Many lung conditions and infections can cause chest X-ray abnormalities. So, all patients with chest X-ray abnormalities must be investigated with sputum smears, NAAT and/or culture.
Incorrect
The correct answer is (c). Chest X-rays alone is NOT sufficient to diagnose pulmonary TB) It needs to be followed by sputum testing. While chest X-rays have fairly high sensitivity for pulmonary TB, its specificity is low. Many lung conditions and infections can cause chest X-ray abnormalities. So, all patients with chest X-ray abnormalities must be investigated with sputum smears, NAAT and/or culture.
Thank you Dr. Pai, the questionnaire was very useful and I could now say where my knowledge in TB disease stands.