DIAGNOSIS
Diagnosis:
TB can be diagnosed in several different ways,
1. Chest X-rays:
Chest X-rays can show whether a person has contracted active tuberculosis pneumonia.
X-rays may also show scarring (fibrosis) or hardening (calcification) in the lungs, which may suggest that the TB is contained and inactive.
2. Analysis of sputum:
Morning sputum samples tend to have the highest yield. Patient should be declared to be at low risk for spreading the infection after three negative smears. Negative smears do not definitively exclude tuberculosis.
Sputum examined on a slide (smear) under the microscope can show the presence of the tuberculosis-like bacteria. Bacteria of the Mycobacterium family, including atypical mycobacteria, have positive stains with special dyes and are known as acid-fast bacteria (AFB). A sample of the sputum also is usually extracted and grown (cultured) in special incubators so that the tuberculosis bacteria can subsequently be identified as tuberculosis or atypical tuberculosis.
3. Skin tests:
These tuberculin skin tests include Tine test and Mantoux test, alsoreferred to as PPD (purified protein derivative) test. A small amount of purified extract from dead tuberculosis bacteria is injected into the body. If the person is healthy, no reactions will occur at the area which he or she has been injected. It is known as a negative skin test. However, if a person is infected with tuberculosis, a swollen and reddened are will occur at the injected area. If this occurs when the person had gone through the tuberculin skin-test for the first time, additional laboratory and x-ray examinations are required to determine if he or she is infected with active tuberculosis.
Here’s something to note: TB skin test cannot be used to determine whether the disease is active or inactive. This determination requires the chest X-rays and/or sputum analysis.
Polymerase chain reaction (PCR) is a special test used to diagnose tuberculosis. This test detects the genetic material of the bacteria. It is extremely sensitive and specific as it is able to detect small amount of TB bacteria.
4. Fluorochrome stains:
Majority of the laboratories in USA use fluorochrome stains such as auramine-rhodamine stain. This technique allows mycrobacteria fluoresce with a bright orange colour. It also can be seen easily under a low-power microscopy,, increasing the sensitivity of the smear detection.
