tbdiagnosis

The correct answer is (c). Sputum expectoration can release infectious aerosols, which are diluted in the open-air or a well ventilated room and are inactivated by UV light in the outdoors.

The correct answer is (d). There is no approved blood test for the diagnosis of active pulmonary TB) IGRAs are tested on blood but only give information on latent TB infection, not active disease.
Reference: World Health Organization. Policy statement: Use of tuberculosis interferon-gamma release assays (IGRAs) in low- and middle-income countries. In. Geneva: World Health Organization; 2011.

The correct answer is (a). Sputum quality and quantity are essential features of a good specimen for TB testing. Five ml of muco-purulent specimen collected in a sterile laboratory approved container is the ideal specimen for sputum microscopy for TB).

The correct answer is (c). Young children cannot expectorate sputum but it is often swallowed overnight. The best specimen is, therefore, a series of two to three consecutive, fasting gastric aspirates.
Reference: Marais BJ, Pai M. Specimen collection methods in the diagnosis of childhood tuberculosis. Indian J Med Microbiol 2006;24:249-51.

The correct answer is (b). The minimum requirement for sputum testing is two specimens taken one hour apart. Previously three consecutive early morning sputum samples were recommended but research has shown that the 3rd sample does not add much to the overall yield (and can increase the risk of patient drop-out).
Reference: Policy statement. Same-day diagnosis of tuberculosis by microscopy. World Health Organization, 2011. (Accessed 2011, at http://whqlibdoc)who.int/publications/2011/9789241501606_eng.pdf.)
Mase SR, Ramsay A, Ng V, et al. Yield of serial sputum specimen examinations in the diagnosis of pulmonary tuberculosis: a systematic review. Int J Tuberc Lung Dis 2007;11:485-95.

The correct answer is (d). Specimens that are unlabeled or do not have a properly filled out form, are rejected by the laboratory. Fixatives, such as formalin, will inactivate any micro-organisms in a tissue sample, therefore, making it unsuitable for culture.

The correct answer is (c). Endometrial issue for culture and histopathology is critical for diagnosing genito-urinary tract TB) Blood (venous or menstrual) is not the appropriate sample as it is very difficult to isolate M. tuberculosis or detect MTB DNA in such samples.

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.

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.

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.

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.

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.

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.