Sputum test: what it is, what it is for and how it is done

The sputum test is a diagnostic test indicated to investigate respiratory diseases, such as tuberculosis or pneumonia, for example, as it allows the evaluation of the characteristics of the sputum, such as fluidity and color, in addition to the presence of microorganisms, such as bacteria or fungi.

This test, also known as sputum culture, is simple and does not require much preparation before it is carried out, it is only recommended that the throat, mouth and nose be cleaned with water only and that the collection be carried out in the morning.

The sputum test is offered free of charge by the SUS, as long as it is medically indicated, but it is also carried out in hospitals or private examination clinics, and the results must be analyzed by an infectious disease specialist, pulmonologist or general practitioner.

What is it for

Sputum examination is indicated to diagnose respiratory diseases, such as:

Additionally, sputum testing may be recommended to monitor the response to treatment for an infection or to check the best antibiotic to combat an infection.

How the exam is carried out

To perform a sputum test, you do not need to prepare much, and it is only recommended:

1. Wash your hands with water and neutral soap;
2. Clean your mouth and throat with water only. The use of antiseptics and toothpaste may interfere with the test results and is therefore not recommended;
3. Remove dentures before cleaning the mouth and throat, in the case of people who wear dentures;
4. Inhale and exhale deeply and slowly 3 times;
5. Cough deeply to loosen the secretions in the lungs;
6. Spit the sputum into the collection jar without touching your lips or fingers to the edges of the jar. Repeat this procedure until the collection bottle reaches a volume of 10 mL.

Generally, collection should be done in the morning before eating or drinking to avoid contaminating the sputum sample. It is recommended to drink plenty of fluids the day before the appointment, to thin the secretions and sleep on your back without a pillow, to facilitate the exit of sputum at the time of collection.

In some people, the doctor may also recommend having a bronchoscopy to collect the necessary amount of sputum from the lungs. Understand what bronchoscopy is and how it is performed.

How to understand the result

The results of the sputum examination indicated in the report take into account the macroscopic aspects of the sample, such as fluidity and color and the microscopic evaluation. The results that may appear in the report are:

• Negative or not detectable: this is a normal result and means that no bacteria or fungi that could cause illness were found;
• Positive: means that bacteria or fungi that can cause disease were found in the sputum sample. In these cases, the type of microorganism is usually also indicated to help the doctor choose an antibiotic or antifungal.

In the case of a negative result, it is very important that the test is still evaluated by a pulmonologist as, if there are symptoms, it could mean that there is an infection caused by viruses that are not identified in the test.