Sputum test for tuberculosis

Pulmonary tuberculosis is an infectious disease caused by Koch's bacilli. In the first stages, the infection may be asymptomatic, but over time, fatigue, lethargy, sweating, pallor of the skin and low temperature appear. In the course of the disease begins coughing, at first dry, then with the discharge of sputum - pathological secretion, indicating the defeat of the tissues of the organ.

What is sputum like in tuberculosis?

By the color of the sputum it is possible to make an assumption about the diagnosis, but a serious examination is required for a final conclusion. In pathologies of the lower respiratory tract, it can vary from colorless or white to canary, yellow-green, green, and with fragments of blood.

For tuberculosis in the initial stages are characterized by transparent vitreous sputum, white indicates the formation of protein and deeper tissue damage, brown, orange-brown with a tinge of rust - the destruction of blood vessels.

Purulent sputum is yellowish-greenish in color, indicating progression of the disease, in which pus is separated. In severe cases, in the last stages of tuberculosis, blood is found in it, and sometimes the sputum is spit out only blood, which is a sign of internal bleeding.

There is another course of tuberculosis, when the accumulation of sputum is not accompanied by a cough. They concentrate in the throat, creating a feeling of lump, causing unpleasant fever and a desire to get rid of, but there is no cough.

Sputum examination for tuberculosis

Blood tests in suspected tuberculosis show only some abnormalities from the norm, such as elevated COE, anemia, leukopenia. Here it is necessary to examine the sputum. What are the methods? [1]

Analysis of secretion for tuberculosis includes investigations:

• macroscopic (determines the volume of secreted secretion, its color, odor, layering, impurities);
• microscopic (to detect acid-fast bacteria);
• bacterioscopic (for Mycobacterium tuberculosis - MBT).

Sputum collection for tuberculosis

Sputum testing for tuberculosis can be done both in public health facilities and private laboratories with a doctor's referral. There is a certain algorithm. For example, to detect mycobacteria, three samples will need to be collected.

For the first, the patient is given a pocket spittoon equipped with a label that includes name, date of birth and collection. Before the procedure, rinse the mouth with water to remove food residues. The container should be brought to the mouth, take 3 deep breaths and strongly cough, spitting sputum into the container. The laboratory technician, after making sure that the volume of material is sufficient (3-5ml), closes the container tightly with a lid and places it in a box for transportation.

The patient is given another spittoon to collect the sample himself the next morning after brushing his teeth, which he takes to the health care facility. Another final sample is taken there. [2]

Part of the sputum is sent to a bacterial laboratory for culture, this method is much more sensitive than the previous method, because it can detect even a single mycobacterium.

How long does a sputum test for tuberculosis take?

A complete sputum test is done for 3 months. This long period of time is due to the fact that tubercle bacilli can grow very slowly. There are also fast methods, which still last at least 42 days.

Sputum bacterioscopy for tuberculosis is simple and economical but takes a long time.

Sputum PCR for tuberculosis

The polymerase chain reaction (PCR) method is very accurate. It determines the presence of the virus with 100% certainty, when other tests may give a negative result if the number of mycobacteria is small. It is based on the detection of bacterial DNA in the samples taken.

Under the influence of enzymes and temperature (50º to 95ºC), two DNA molecules are formed from one. This takes 3 minutes. It takes 30-40 cycles, which means one and a half to two hours, to get a result. The PCR method detects tuberculosis at the earliest stages of its development.

Microscopic examination of sputum in tuberculosis

Microscopic examination of sputum reveals eosinophils - one of the subtypes of leukocytes, a large number of erythrocytes in pulmonary hemorrhage, elastic fibers, Kurshman spirals, Ehrlich's tetrad.

Although there are many acid-fast bacteria other than tuberculosis bacteria in nature, this is one of the main methods of tuberculosis detection, as it is characterized by simplicity and speed (from one hour). Microscopic examination of sputum allows to identify the most dangerous for the surrounding patients, as well as to trace the dynamics of treatment. [3]

Sputum result for tuberculosis

A positive sputum test result means that Koch's bacillus has been detected and this confirms the diagnosis. Negative indicators do not exclude it and require other studies: tuberculin test, immunoenzyme analysis, histological, fluorography, X-ray, computer tomography.

What is the difference between sputum of pneumonia and tuberculosis?

In pneumonia, mucous and mucopurulent sputum is most often observed, but blood may be present not only in tuberculosis, but also in focal pneumonia. Orange-brown color is inherent in both croup inflammation of the lungs and tuberculosis.

Both pathologies are characterized by fibrinous clots in the sputum, but in pneumonia there are no rice-like cells (Koch's lenses), there is less protein and bile may be detected.