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The UK guidelines are formulated according to the Heaf test: In patients who have had BCG previously, latent TB is diagnosed if the Heaf test is grade 3 or 4 and have no signs or symptoms of active TB; if the Heaf test is grade 0 or 1, then the test is repeated.
Clinical evaluation and additional tests (such as a chest radiograph, sputum smear, and culture) are needed to differentiate between a diagnosis of latent TB or active TB. Advantages of the test are: Requires a single patient visit to draw a blood sample. Results can be available within 24 hours.
The results of this test must be interpreted carefully. The person's medical risk factors determine at which increment (5 mm, 10 mm, or 15 mm) of induration the result is considered positive. [12] A positive result indicates TB exposure. 5 mm or more is positive in An HIV-positive person; Persons with recent contacts with a TB patient
[1] [9] People with latent TB do not spread the disease. [1] Active infection occurs more often in people with HIV/AIDS and in those who smoke. [1] Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of bodily fluids. [10] Diagnosis of latent TB relies on the tuberculin skin test (TST) or blood tests ...
The medical history includes obtaining the symptoms of pulmonary TB: productive, prolonged cough of three or more weeks, chest pain, and hemoptysis.Systemic symptoms include low grade remittent fever, chills, night sweats, appetite loss, weight loss, easy fatiguability, and production of sputum that starts out mucoid but changes to purulent. [1]
The test is then read 48 to 72 hours later by measuring the size of the largest papule or induration. Indications are usually classified as positive, negative, or doubtful. [2] Because it is not possible to control precisely the amount of tuberculin used in the tine test, a positive test should be verified using the Mantoux test. [3]
The false positive rate (FPR) is the proportion of all negatives that still yield positive test outcomes, i.e., the conditional probability of a positive test result given an event that was not present. The false positive rate is equal to the significance level. The specificity of the test is equal to 1 minus the false positive rate.
Mycobacterium tuberculosis (M. tb), also known as Koch's bacillus, is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. [ 1 ] [ 2 ] First discovered in 1882 by Robert Koch , M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid .