Respiratory Cultures: Screening Criteria and Sputum Specimen Collection
Sputum and Tracheal Aspirate specimens are subject to screening for specimen acceptability. Unacceptable specimens are rejected for culture, and the results of the unacceptable screening smears are called to the patient's care team.
To increase the likelihood of obtaining an acceptable specimen, please review Sputum Collection Methods below prior to obtaining specimen.
The following criteria are used to determine acceptance or rejection, using a Gram-stained smear of the specimen:
Sputum
| PMN/Low Power Field |
Squamous Epithelial Cells/Low Power Field |
Acceptable? |
Comments |
| <10 |
<10 |
NO |
Gram-stain does not suggest ongoing inflammatory process; Specimen processed by request only for neutropenic patients (ANC <0.5).
|
| 10-25 |
<10 |
YES |
|
| >25 |
<10 |
YES |
| >25 |
10-25 |
YES |
| OTHER |
NO |
If No Organisms are Seen (on Oil Immersion) the
care team is contacted: Specimen is Unacceptable due to Low Culture Yield.
If yeast are the only organisms observed (on oil immersion) the care team is contacted to determine need for culture.
|
Tracheal Aspirate
|
Adult Patients
(>16 y)
|
No Organisms Seen on Oil Immersion
OR
Yeast Only Seen on Smear
OR
>10 Squamous Epithelial Cells/LPF
|
Rejected |
|
<10 Epithelial Cells/LPF
ANY PMN
|
Accept |
|
Pediatric Patients
(<16 y)
|
No Organisms Seen on Oil Immersion
OR
Yeast Only Seen on Smear
|
Rejected |
|
Any PMN
Any Squamous Epithelial Cells/LPF
|
Accept |
Sputum Specimen Collection
Approximately 10% of sputum samples submitted for routine bacterial culture are rejected based on specimen quality. Specimen quality is determined based on the relative numbers of squamous epithelial cells to polymorphonuclear lymphocytes. The quality of sputum specimens for all types of culture (bacterial, fungal, mycobacterial) may be improved by using the following collection guidelines:
- If possible, have the patient rinse mouth and gargle with WATER prior to sputum collection (no chemical mouth washes/gargles)
- Instruct the patient NOT to expectorate saliva or postnasal discharge into the container
- Collect specimen resulting from DEEP COUGH in sterile screw-cap cup or other suitable sterile collection assembly.
