Write-up by B Krishan
As already explained, there are two entities of the disease, infection and clinical manifestations, i.e., when the illness is active. Hence, it is critical to establish the activity of the disease, which is essential for starting the treatment of tuberculosis. The treatment is a long 1 and needs a combination of three-four drugs in all the circumstances. The following tests aid in establishing the activity of the disease. Nevertheless, as 1 can see, all tests have their own limitations, and as a result, 1 can not rely on a single test.
1. Sputum examination for tubercle bacilli
It really should be carried out at least 3-4 times. Approximately five,000 to 10,000 tubercle bacilli are needed per ml of sputum for the detection of tubercle bacilli in a smear. Hence, repeated examinations of sputum are advised.
2. Sputum culture for tubercle bacilli
Despite the fact that this test is a lot more sensitive than the direct smear examination, it is a lot more time-consuming, and needs about 68 weeks. Once more, as in a direct smear examination, 3-four cultures of tubercle bacilli may well be needed to obtain positive results. A well-equipped laboratory and trained staff is required for carrying out this test.
three. Chest X-ray
It should be carried out in all the suspected cases of tuberculosis. 1 really should not rely solely on the chest X-ray report as proof of the activity of the disease. Other tests, including symptoms and signs of the illness, should be taken into account.
four. Tuberculin / Mantoux test It has a limited value. Nevertheless, a negative tuberculin test might prove to be extremely valuable in some of the cases, to exclude the diagnosis of tuberculosis in a specific case.
5. ELISA (enzyme-linked immunosorbent assay) test for tuberculosis
It is one of the serological tests and detects antibodies against tubercle bacilli. It is extremely helpful to detect hidden circumstances of tuberculosis, specially extra pulmonary i.e., when the lesion of tuberculosis is outside the lungs. The accuracy of this test is 90-95 per cent, and it does not turn into positive with the administration of the BCG vaccination.
Nevertheless, like other tests, this test too has its own limitations. It may possibly be false-positive, if the patient has an infection, with other varieties of organisms related to the group of tubercle bacilli, or due to some non-distinct reaction. Similarly, the test may possibly turn into false-negative when there are extremely low levels of circulating antibodies, due to suppression of the immune program of the body.
Hence, in view of the limitations of the test, this test need to be interpreted keeping the clinical profile and other investigations in view.
What is the tuberculin skin test?
This test detects the 'infected' cases of tuberculosis by eliciting a hypersensitivity reaction in patients who are already infected with tubercle bacilli. In this test, a lot more precisely the Mantoux test, purified proteins isolated from tubercle bacilli referred to as 'tuberculins' are injected intracutaneously on the upper surface of the forearm. Out of a number of tuberculin tests, the Mantoux is most commonly utilized, since by and large its results are highly reliable. This test will have small value in places where there is a high incidence of tuberculosis, i.e., at such places virtually every person can be expected to be infected with tubercle bacilli. Even so, it has value otherwise. Those instances which are tuberculin negative, may not be suffering from tuberculosis, and in such cases, one should believe of other pathology in a concerned patient.
In about 48-72 hours, following the injection of the test, an allergic reaction occurs as a raised, hard red spot at the internet site of injection. The size of this location ought to be carefully measured, and an area of 10 mm, roughly about half an inch or far more in diameter, indicates that the reaction is positive. Only the in duration (raised area) ought to be measured with regard to its width. The redness around the raised region need to be avoided while taking measurements. Ideally, a trained and experienced technician, specifically 1 who specifically deals in carrying out tuberculin tests, is needed. An in duration of much less than 7 mm is considered negative, while in duration between 7-10 mm, may be regarded as a borderline or a doubtful case of tuberculin positive, and such cases will need further tests, for exclusion, or for establishing a diagnosis of tuberculosis.
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