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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
A meta-analysis with 1,595 inpatients and outpatients showed 70% sensitivity and 90% specificity for TB diagnosis in people living with HIV for Fujifilm SILVAMP TB LAM. [40] As of 2020, the test showed a high positive predictive value (95.2%) in HIV-negative outpatients. [41] Large prospective studies are on the way. [42]
If there is any question of active TB, sputum smears must be obtained. Therefore, any applicant might have findings grouped in this category, but still have active TB as suggested by the presence of signs or symptoms of TB, or sputum smears positive for AFB. [2] The main chest X-ray findings that can suggest inactive TB are: [2] 1.
T-SPOT.TB counts the number of antimycobacterial effector T cells, white blood cells that produce interferon-gamma, in a sample of blood.This gives an overall measurement of the host immune response against mycobacteria, which can reveal the presence of infection with Mycobacterium tuberculosis, the causative agent of tuberculosis (TB).
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 test may be falsely negative in those with sarcoidosis, Hodgkin's lymphoma, malnutrition, and most notably, active tuberculosis. [13] Interferon gamma release assays , on a blood sample, are recommended in those who are positive to the Mantoux test. [ 105 ]
If you still test negative, wait 48 more hours and test for a final time. In both cases, if you’d rather not wait, you can obtain a PCR, or polymerase chain reaction, test at a doctor’s office.
The equivalent Mantoux test positive levels done with 10 TU (0.1 mL 100 TU/mL, 1:1000) are 0–4 mm induration (Heaf 0-1) 5–14 mm induration (Heaf 2) >15 mm induration (Heaf 3-4) The Mantoux test is preferred in the United States for the diagnosis of tuberculosis; multiple puncture tests, such as the Heaf test and Tine test, are not recommended.