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Intrapartum Group B

GBS, Intrapartum, Vaginal, Prenatal, Group B Strep, Streptococcus

Test Codes

EPIC: LAB7677

Department

Microbiology

Instructions

• This test is ONLY for intrapartum screening when the Group B Streptococcus (GBS) status of the mother is unknown at the time of delivery.
• Universal antepartum screening for GBS at 36-37 weeks of gestation is the standard of care for preventing neonatal GBS disease, order Strep Screen, Group B

Specimen Collection Criteria

Collect: Two vaginal-rectal swab specimens as described below.

• Using two BBL liquid stewart swabs, first sample the vaginal introitus and then the anorectum. Place both swabs into BBL liquid stewart transport medium.

Physician Office/Draw Specimen Preparation

Maintain swab specimen at room temperature (20-26°C or 68-78.8°F).

Preparation for Courier Transport

Transport: Swabs in BBL liquid stewart transport medium at room temperature (20-26°C or 68-78.8°F).

Rejection Criteria

• Specimens received at room temperature greater than 24 hours after collection.
• Swabs on which the specimen appears to have dried.
• Specimens not in bacterial transport medium.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 6 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Room Temperature (20-26°C or 68-78.8°F): 7 days

Laboratory

Dearborn Microbiology Laboratory
Taylor, Trenton and Wayne sent to Dearborn Microbiology Laboratory for testing.

Royal Oak Microbiology Laboratory
Farmington Hills, Grosse Pointe, and Troy sent to Royal Oak Microbiology Laboratory for testing.

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 2 hours of receipt in the Laboratory.

Routine results available within 24 hours.

Reference Range

No Group B Streptococcus recovered.

Test Methodology

Nucleic Acid Amplification (FDA Approved; Xpert GBS) 

Culture will be performed on all positive molecular tests for GBS. If GBS is isolated, antimicrobial susceptibility testing performed. 

Interpretation

The presence of Group B Streptococcus in vaginal-rectal specimens obtained from pregnant women at the time of delivery has been associated with invasive perinatal disease.

Clinical Utility

Routine antepartum GBS screening requires incubation in enrichment broth media prior to testing, which results in a 2-3 day turnaround time for results. For women who have had no prenatal care, preterm delivery, or unknown GBS test results, intrapartum testing can provide results in time to administer antibiotics before delivery, if required.

The intrapartum screening test is ONLY for detecting Group B Streptococcus in women with unknown GBS test results at the time of delivery. For routine GBS screening, providers should order Strep Screen, Group B.

Clinical Disease

Group B Streptococcus (Streptococcus agalactiae) is a major cause of perinatal bacterial infections. It causes endometritis, amnionitis, and urinary tract infections in parturient women and systemic and focal infections in infants from birth until 3 or more months of age. Two distinct forms of invasive disease occur in neonates. Early-onset disease is often characterized by respiratory distress, apnea, shock, pneumonia, and, occasionally, meningitis, and its onset usually occurs within the first 24 hours of life (range, 0 to 6 days). Late-onset disease, which typically occurs after one week of age (range, 7 days to 3 months), is frequently manifested as occult bacteremia or meningitis; other focal infections, such as osteomyelitis, septic arthritis, and cellulitis, can also occur. Group B Streptococcus also cause infections in adults, particularly the elderly, those with diabetes, malignancy, or other immunocompromising conditions.

Incubation Period

The incubation period of early-onset disease is less than 6 days. In late-onset disease the incubation period from GBS acquisition to disease is unknown. Onset usually occurs from 7 days to 3 months of age.

Transmission

Transmission from mother to infant occurs in utero shortly before delivery or during delivery. After delivery, person-to-person transmission can occur. Although uncommon, GBS can be acquired in the nursery from colonized infants or hospital personnel (probably via hand contamination), or in the community. The risk of early-onset disease is increased in pre-term infants born at less than 37 weeks gestation, in those born after the amniotic membranes have been ruptured for more than 18 hours and in infants born of women with intrapartum fever or chorioamnionitis, multiple births (such as twins), or GBS bacteriuria. Low or absent concentration of type-specific serum antibody also appears to be a predisposing factor. The period of communicability is unknown, but it may extend throughout the duration of colonization or of disease. Infants can remain colonized for several months after birth and after treatment of symptomatic infections.

Reference

1. Puopolo, K.M., R. Lynfield, R. et al.,2019, Management of infants at risk for Group B Streptococcal Disease, American Academy of Pediatrics, Committee on Fetus and Newborn Children, Pediatrics, https://doi.org/10.1542/peds.2019-2350
2. ACOG, 2020, Prevention of Group B Streptococcal Early-Onset Disease in Newborns, ACOG Committee Opinion, American College of Obstetricians and Gynecologists. Obstetrics & Gynecology, 135(2): e51-71.
3. CDC. 2010. Prevention of Perinatal Group B Streptococcal Disease. Revised Guidelines from CDC.MMWR: Recommendations and Reports. 59(RR11); 1-36.
4. Filkins L, Hauser J, Robinson-Dunn B, Tibbetts R, Boyanton B, Revell P. 10 March 2020. Guidelines for the Detection and Identification of Group B Streptococcus. American Society for Microbiology. https://asm.org/Guideline/Guidelines-for-the-Detection-and-Identification-of.

CPT Codes

87653

Contacts

Last Updated

11/28/2022