How To Establish The Diagnosis Of Tuberculosis?

As already explained, there are two entities of theother types of organisms related to the group of
disease, infection and clinical manifestations, i.e., whentubercle bacilli, or due to some non-specific reaction.
the disease is active. Hence, it is important toSimilarly, the test may become false-negative when
establish the activity of the disease, which isthere are very low levels of circulating antibodies, due
important for starting the treatment of tuberculosis.to suppression of the immune system of the body.
The treatment is a long one and needs a combinationHence, in view of the limitations of the test, this test
of 3-4 drugs in all the cases. The following tests helpshould be interpreted keeping the clinical profile and
in establishing the activity of the disease. However,other investigations in view. What is the tuberculin
as one can see, all tests have their own limitations,skin test? This test detects the 'infected' cases of
and therefore, one cannot rely on a single test. 1.tuberculosis by eliciting a hypersensitivity reaction in
Sputum examination for tubercle bacilli It should bepatients who are already infected with tubercle bacilli.
carried out at least 3-4 times. Approximately 5,000 toIn this test, more precisely the Mantoux test, purified
10,000 tubercle bacilli are required per ml of sputumproteins isolated from tubercle bacilli called 'tuberculins'
for the detection of tubercle bacilli in a smear. Hence,are injected intracutaneously on the upper surface of
repeated examinations of sputum are advised. 2.the forearm. Out of several tuberculin tests, the
Sputum culture for tubercle bacilli Although this test isMantoux is most commonly used, since by and large
more sensitive than the direct smear examination, itits results are highly reliable. This test will have little
is more time-consuming, and requires about 68value in places where there is a high incidence of
weeks. Again, as in a direct smear examination, 3-4tuberculosis, i.e., at such places almost every person
cultures of tubercle bacilli may be required to obtaincan be expected to be infected with tubercle bacilli.
positive results. A well-equipped laboratory andHowever, it has value otherwise. Those cases which
trained staff is required for carrying out this test. 3.are tuberculin negative, may not be suffering from
Chest X-ray It should be carried out in all thetuberculosis, and in such cases, one should think of
suspected cases of tuberculosis. One should not relyother pathology in a concerned patient. In about
solely on the chest X-ray report as proof of the48-72 hours, following the injection of the test, an
activity of the disease. Other tests, includingallergic reaction occurs as a raised, hard red spot at
symptoms and signs of the disease, must be takenthe site of injection. The size of this area should be
into account. 4. Tuberculin / Mantoux test It has acarefully measured, and an area of 10 mm, roughly
limited value. However, a negative tuberculin testabout half an inch or more in diameter, indicates that
may prove to be highly valuable in some of thethe reaction is positive. Only the in duration (raised
cases, to exclude the diagnosis of tuberculosis in aarea) should be measured with regard to its width.
particular case. 5. ELISA (enzyme-linkedThe redness around the raised area must be avoided
immunosorbent assay) test for tuberculosis It is onewhile taking measurements. Ideally, a trained and
of the serological tests and detects antibodies againstexperienced technician, especially one who specifically
tubercle bacilli. It is highly useful to detect hiddendeals in carrying out tuberculin tests, is required. An in
cases of tuberculosis, especially extra pulmonary i.e.,duration of less than 7 mm is considered negative,
when the lesion of tuberculosis is outside the lungs.while in duration between 7-10 mm, may be
The accuracy of this test is 90-95 per cent, and itconsidered a borderline or a doubtful case of
does not become positive with the administration oftuberculin positive, and such cases need further tests,
the BCG vaccination. However, like other tests, thisfor exclusion, or for establishing a diagnosis of
test too has its own limitations. It may betuberculosis.
false-positive, if the patient has an infection, with