Sputum Analysis

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Sputum analysis


Sputum is a substance comprised of mucous, foreign matter, and saliva that is found in the lungs or bronchial tree. A sputum analysis is a group of tests performed in a laboratory on a sputum specimen obtained from a sick patient. A portion of the sputum specimen is stained and put on a slide for examination of cells and organisms. Another portion of the specimen is put on an agar plate to see if infectious organisms grow and can be identified. Some of the sputum may be placed in special solutions to test for specific diseases.

TermDescriptionAssociated with
source: Rothstein, J.M., S.H. Roy, and S.L. Wolf. The Rehabilitation Specialist's Handbook. 2nd ed. Philadelphia: F.A. Davis Co., 1998.
FetidFoul-smelling, typical ofBronchiectasis, lung
anaerobic infectionabscess, or cystic fibrosis
FrothyWhite or pink-tinged, foamy, thin sputumPulmonary edema
HemoptysisExpectoration of blood or bloody sputum; amount may range from blood-streaked to massive hemorrhageA variety of pathologies
MucoidWhite or clear, not generally associated with broncho-pulmonary infectionChronic cough (acute or chronic bronchitis, cystic fibrosis)
PurulentPus, yellow or greenish sputum, often copious and thickAcute and chronic infection
RustyDescriptive of the color of sputum (also called prune juice)Pneumococcal pneumonia


The purpose of a sputum analysis is to help identify microorganisms that are causing respiratory disease or infection . The most common reason for obtaining a sputum specimen is to test for infectious tuberculosis . A sputum analysis, however, is also used to identify disease-producing organisms that may be causing pneumonia , bronchitis, lung abscess , or other respiratory disease. A sputum analysis may be used to identify conditions such as: aspiration pneumonia, histoplasmosis, cryptococcosis, blastomycosis, mycoplasma pneumonia, plague, mycobacterial infection, and pneumocystic pneumonia.


A sputum specimen should not be collected immediately following a meal because the sputum or the process of collecting the sputum may cause gagging and vomiting.

Good hand washing and the use of gloves are necessary when collecting a sputum specimen. A disposable gown and filter-mask should be worn if reactivated infectious tuberculosis is suspected.

About 1 teaspoon (3-5 cc) of sputum should be collected to have a sufficient quantity for proper testing. The specimen cup should not be left at the bedside for the client to randomly spit into. Specimens must be fresh and taken immediately to the laboratory for effective analysis.


Agar —A gelatinous culture media used in laboratories to grow microorganisms such as bacteria.

Bronchoscopy —The examination of the inside of a client's airway and bronchus by a physician using a flexible scope connected to a light source and video camera.

Sputum —A substance coughed up from the airway, bronchi or lungs comprised of saliva, foreign matter, and mucous.

The specimen must be coughed up from the lungs or bronchial tree. It can be mixed with saliva, but a specimen that is only saliva is not adequate for proper testing.

An infant or young child cannot cough up sputum on command. Sputum specimens must be obtained with a nasal-pharyngeal aspirator connected to a mucous trap or by bronchial washings performed during a bronchoscopy . If using a nasal-pharyngeal aspirator, the tubing must have a one way valve on the testers side of the tubing to prevent the inhalation of infected droplets from the patient or a trap that connects directly to a suction apparatus.

The use of antibiotics , anti-inflammatory drugs, or steroids may affect the test results. If the patient is receiving any of these medications, the physician should be notified, and it should be notified on the laboratory slip.


The patient should take three slow deep breaths and cough forcefully with the exhalation of the third breath. Sputum that is coughed up should be spit directly into the sterile specimen cup. The process is repeated until the required amount of sputum is collected. The cap is then placed on the specimen cup.

If the patient has difficulty raising sputum, the physician should be notified. Some patients may require postural drainage and cupping to loosen and drain secretions. Others may require an aerosol treatment with saline or medications to open the air sacs and allow drainage of the sputum before it can be collected. In certain cases the physician may elect to perform a bronchoscopy to collect the sputum for analysis. A bronchoscopy is performed in a special setting where the client can be sedated and monitored during the procedure.

A nasal-pharyngeal mucous trap is used to collect sputum from an infant or young child that cannot understand instructions. A small tube is inserted through the nasal passage and into the pharynx. This process usually stimulates the infant to cough. As the child coughs up sputum, it is pulled through the tubing and into a mucous trap. The mucous trap is placed in a plastic biohazard specimen bag that is sealed, labeled, and sent to the lab for analysis. If a specimen from an infant can not be collected, the physician should be notified. The sputum may need to be collected through a bronchoscope by the physician.

Special testing may require variance in the sputum collection procedure. For example, sputum for viral studies may require that the client gargles and expectorates with a nutrient broth. The medical setting's lab manual should be consulted for instructions to collect sputum for special testing.


The procedure is explained to the patient. Fluid intake should be encouraged the night before the test. The specimen should be obtained in the morning before meals. The patient should abstain from smoking, eating, or chewing gum before the specimen collection. If the patient has dentures, they should be removed. The patient rinses his mouth with plain water before the test to clear debris from the mouth. The patient is seated in an upright position. A capped sterile specimen cup is placed near the patient. Good handwashing and the use of gloves is necessary for this procedure. Other protective gear is used as instructed (i.e., for known tuberculosis client with potentially reactivated tuberculosis). The laboratory manual of the medical setting should be consulted for specific specimen directions.


The patient should be allowed to relax and breathe quietly. The specimen cup is labeled with the patient's name, doctor, time, date, and type of specimen. The specimen cup is placed in a biohazard labeled plastic sealed bag. The specimen does not need to be refrigerated but should be transported to the lab immediately for testing. Good handwashing is necessary after the procedure. Used tissues and gloves should be placed in a contaminated trash bag that can be sealed and discarded.


There are no complications to obtaining a non-invasive sputum specimen. Complications of obtaining a specimen by nasal tracheal aspiration or bronchoscopy are rare but may include trauma to the throat or tracheal tissue and/or secondary infection.


A sputum analysis, when used in conjunction with other tests such as chest x-rays or blood cultures, is an important diagnostic tool. It is an effective method for identifying unknown organisms that are causing respiratory infections or disease. Identification of the organism allows proper selection of antibiotic or other drug therapy to treat specific respiratory disease and provide a positive outcome for the client. Improper collection or handling of a sputum specimen may invalidate the test results.

Health care team roles

A sputum specimen is usually collected by a licensed nurse or respiratory therapist in the medical setting. Other medical personnel, however, such as medical office technicians or other non-professional staff can be taught the correct method for obtaining a sputum specimen. A patient or patient's family can be trained to collect a sputum specimen in the home. The specimen should be taken promptly to a lab for analysis. A laboratory technician will prepare the specimen for analysis, and a pathologist will ultimately be responsible for analyzing the sputum specimen.



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Mary Elizabeth Martelli, R.N., B.S.