Tuberculosis is a chronic disease. i.e. a disease of gradual onset and long duration. The primary infection, in young children, usually goes unnoticed clinically. The primary tuberculosis lesions (pathological changes in tissues) commonly become inactive leaving no residual changes. However, it may also progress to active pulmonary (lung) tuberculosis and further spread through lympho-haematogenous (blood) path to involve the nervous system, particularly the meninges (membranous coverings of brain and spinal cord).
Pulmonary tuberculosis, is characterised by a variable and often a symptomatic (symptomless) course with exacerbation (increase in severity) and remissions (abatement of symptoms). Clinically, it is confirmed by presence of tubercle bacilli in sputum (matter ejected from lungs, trachea and bronchi through mouth). Abnormal X-Ray densities indicative of pulmonary involvement occur before clinical manifestations (clinical signs and symptoms). The patients may have cough, easy fatiguability (gets tired with little effort). fever. loss of weight and appetite, hoarseness of voice, and chest pain. The patient may bring out blood in sputum, particularly in advanced stages. Most often, the patient, usually from a low income family, presents himself before a doctor in advanced stage.
Sputum examination by direct microscopy is now considered the method of choice for finding out cases of tuberculosis. Under Indian Tuberculosis control programme microscope examination of sputum is performed as a routine on patients who attend hospitals and primary health centres with the following chest symptoms:
- Cough lasting for more than 4 weeks
- Continuous fever
- Chest pain
- Blood in sputum
Tuberculin Test is undertaken to detect tuberculosis. What is the test and how it is administered is discussed below :
Tuberculin Test : Persons infected with tuberculosis will react to a low dose of tuberculin test. One of the tests, is Mantoux intradermal test This is the most widely used and found satisfactory for epidemiological studies. Into the superficial layers of the skin. 0.1 ml of a standard dilution of old tuberculin (OT) or purified protein derivative (PPD) is injected. Special syringes are used for the purpose. If you notice in duration (slight hardening, reddish in colour) of more than 6 mm in diameter after 72 hours, it is considered a positive test. The reaction may be negative in critically ill tuberculosis patients and during certain infectious diseases such as measles.
Extra-pulmonary (other than lung) tuberculosis is much less common than the tuberculosis of the lungs. It includes tuberculous meningitis (infection of the protective covering of the spinal cord), involvement of bones and joints, intestines. kidneys. larynx (voice box) etc. Diagnosis is by recovery of tubercle bacilli from lesions or secretions from these lesions.
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