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Sputum Culture Test

Last updated May 9, 2019

The Sputum Culture Test is a routine test to detect bacterial infection of the lower respiratory tract. It is used to diagnose lower respiratory tract infection and to determine the appropriate antibiotic treatment.


What are the other Names for this Test? (Equivalent Terms)

  • Bacterial Sputum Culture Test
  • Respiratory Bacterial Culture Test
  • Respiratory Culture Test

What is Sputum Culture Test? (Background Information)

  • The lower respiratory tract is generally defined as the region below the laryngeal prominence (or the Adam’s apple). Sputum or phlegm is the thick mucus originating from the lower respiratory tract
  • The lower respiratory tract should essentially lack microorganisms, which is in contrast to the upper respiratory tract that normally houses several types of microbes. It can indicate lower respiratory infection if bacteria or other pathogens are present
  • The sputum or phlegm is collected, and it is cultured to test for bacteria. Culturing entails smearing the sputum on a Petri dish and observing for any signs of growth. Different media and conditions may be used to differentiate between specific types of microbes
  • Difficulty arises when distinguishing between a pathogenic lower respiratory tract infection and contamination from normal upper respiratory tract bacteria. A good indicator is the presence of upper respiratory tract epithelial cells, which could indicate contamination
  • The Sputum Culture Test is a routine test to detect bacterial infection of the lower respiratory tract. It is used to diagnose lower respiratory tract infection and to determine the appropriate antibiotic treatment

What are the Clinical Indications for performing the Sputum Culture Test?

Following are the clinical indications for performing a Sputum Culture Test:

  • Cough
  • Wheezing
  • Headaches, muscle aches
  • Fever, chills
  • Chest pain
  • Nausea, vomiting
  • Fatigue
  • Shortness of breath

How is the Specimen Collected for Sputum Culture Test?

Following is the specimen collection process for Sputum Culture Test:

Sample required: Sputum or phlegm

Process:

  • Coughing and spitting out phlegm (expectoration)
  • Suctioning phlegm through a catheter (suctioning)
  • Collection of phlegm using a bronchoscope (bronchoscopy)

Preparation required:

  • No food should be consumed at least 6 hours prior to a bronchoscopy procedure
  • The duration of fasting for collecting phlegm through a suctioning method, shall be determined by the healthcare provider

No specific preparation is required for phlegm collection through coughing; although, the preferred sample is one that is collected as soon as one wakes up in the morning 

What is the Significance of the Sputum Culture Test Result?

  • A positive Sputum Culture Test indicates bacterial growth and thus, lower respiratory tract infection

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results based on the overall clinical scenario.  

Additional and Relevant Useful Information:

  • The Sputum Culture Test is specific for bacterial infection of the lower respiratory tract. To identify any viral or fungal infections, other tests may be required to be performed

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Nov. 12, 2014
Last updated: May 9, 2019