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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Culture, Sputum with Gram Stain

Test Code(s): SPUCS / HCSPUCS

CPT Code(s): 87070, 87205; Additional CPT codes may be added for processing, identification, and susceptibility testing.

Test Description: Test Component:

Gram stain and culture.


Methodology: Culture, Microscopy

Clinical Significance: Lower respiratory cultures aid in the differential diagnosis of bacterial, tuberculous, and fungal pneumonia. If smears and cultures are negative for pathogens, the physician is alerted to look for other causes of chest disease such as tumors or viral infections.

Days Performed: Daily, 24 hours.

Turnaround Time: Routine: Preliminary report: 24 hours. Cultures with no growth or endogenous flora will be reported after 48 hours. Reports on specimens from which pathogens are isolated require a minimum of 48 hours for completion.


Specimen Requirements

Specimen: Expectorated, suctioned or induced sputum, tracheal aspirate

Collection Container: Preferred: Sterile screw cap container

Specimen Transport: Transport specimen to UWHC Microbiology (B4/231) within 2 hours of collection. Refrigerate sample if transport time will exceed 2 hours.

Unacceptable Criteria: See Additional Information section for rejection criteria. Also, more than one specimen received from the same patient within 24 hours is not acceptable.

Stability: Ambient: 2 hours
Refrigerated: 24 hours
Frozen: Not acceptable


Interpretation

Expected Results:

Endogenous respiratory flora

Test Limitations:

Since expectorated sputum, tracheal aspirations, and most bronchial washings are contaminated with endogenous oropharyngeal flora (which includes most of the common lower respiratory tract pathogens), cultures of such specimens are neither particularly sensitive nor specific for the diagnosis of bacterial pneumonia and results should be interpreted with caution.

 

Blood cultures are recommended for the diagnosis of pneumonia, especially for hospitalized patients and those with severe community acquired pneumonia (CAP).  

Additional Information:

For patients with an ET tube or tracheostomy, quantitative mini-BAL by RT or bronchoscopic BAL are preferred methods of specimen collection.

 

A Gram stain is always performed to determine the acceptability of the specimen.

 

The following criteria are used in rejecting a specimen:

 

INPATIENTS or ED: If there are >10 squamous epithelial cells per low power field and they outnumber the WBCs, the specimen will not be cultured and a screen will NOT be performed. If less than 10 squamous epithelial cells and either no organisms or only yeast are seen on Gram stain, the specimen will not be cultured. If WBCs outnumber squamous epithelial cells and no predominating pathogen is present on Gram stain, the specimen will not be cultured.

NOTE: If WBC outnumber squamous epithelial cells and the culture will not be performed, the specimen will be screened for MSSA/MRSA and Psuedomonas aeruginosa.

 

OUTPATIENTS: If there are >10 squamous epithelial cells per low power field and they outnumber the WBC, the specimen will not be cultured. If less than 10 squamous epithelial cells and either no organisms or only yeast are seen on Gram stain, the specimen will not be cultured. If WBC outnumber squamous epithelial cells and no predominating pathogen is present on Gram stain, the specimen will not be cultured.

 

Presence or absence of endogenous upper respiratory flora will be reported.

 

Susceptibility testing is performed based on lab protocols.

 

Special methods are necessary for detection of mycobacteria, Legionella, filamentous and dimorphic fungi, Nocardia, and Mycoplasma. See individual entries for additional information. 

Culture-Sputum

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