Overview
MDL Test Name
Group B Screen by Culture
MDL Test Code
GBS
Ask at Order Questions
Does the patient have a penicillin allergy?
Is the patient >34 weeks gestation?
Specimen Source
Rectovaginal
Specimen Requirements
Container/Tube
ESwab
Specimen Volume (minimum)
N/A (swab specimen)
Must have swab present in container
Sample Stability Time
48 hours
Transport/Storage Conditions
Refrigerated (2 – 8°C)
Ambient (20 – 25°C)
Patient Preparation / Collection Instructions
Remove swab from the packaging, careful not to contaminate it. Collect both a vaginal AND rectal specimen, using a single swab. Swab the lower vagina (vaginal introitus), followed by the rectum (swab should be inserted through the anal sphincter) preferably using the same swab. Move the swab from side to side, or rotate the swab at the collection site, allowing several seconds for absorption of organisms by the swab. Place the swab into transport tube and label it appropriately.
NOTE: Cervical, perianal, perirectal, or perineal specimens have been shown to be less sensitive than co-collection of vaginal and rectal specimens and are NOT acceptable.
Refer to the WSU MDL ESwab Collection Guide
Performance
Days Performed
Daily; Monday – Sunday
Report Available (TAT) – (Once received at MDL)
3 – 4 Days
Specimen Retention Time
7 days
Method Description
Conventional aerobic bacterial culture technique with selective and non-selective media.
Identification methods (when appropriate) may include any of the following: conventional biochemical testing, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, commercial identification panels.
Reference Values
No growth of Group B Strep (Streptococcus agalactiae)
Cautions
This test is for perinatal screening to detect GBS colonization. For diagnosis of GBS disease in nonpregnant adults and in neonates, routine culture of the symptomatic body site should be ordered.
Detects only the presence or absence of Group B Streptococcus.
NOTE: Susceptibility testing is not routinely performed for Group B Screen by culture. Susceptibility testing is only performed when ‘Ask at order question’, Penicillin allergy? Is answered ‘yes’ or if an ‘add-on’ request/order is submitted within 7 days of the ‘final date’ of the report.