Rapid intrapartum test for maternal group B streptococcal colonisation and its effect on antibiotic use in labouring women with risk factors for early-onset neonatal infection (GBS2): cluster randomised trial with nested test accuracy study
Authors: Daniels Jane P. , Dixon Emily , Gill Alicia , Bishop Jon , Wilks Mark , Millar Michael , Gray Jim , Roberts Tracy E. , Plumb Jane , Deeks Jonathan J. , Hemming Karla , Khan Khalid S. , Thangaratinam Shakila ,   on behalf of the GBS2 Collaborative Group, Ahmed Khaled , Dodds Julie , D’Amico Maria , Tryposkiadis Kostas , Whiley Angela , Moore Patrick , Munetsi Ruvimbo Lorraine , Karkhanis Pallavi , Deans Anne , Sharma Sanjula , Wright Gemma , Subramanian Manjula , Ray Irene , Datta Dibyenda , Lacey Lauren , Pepper Johnathon , Mason Ruth , Shah Neil , Anwar Katharina , Navaneetham Neena , Husain Shad , Bennett Phillip , Masson Geraldine , Raykova Hristina , Hogg Matthew , Dawalatly Bashir , Thirumalaikumar Lakshmi , Townsend Kate , Collins Gerry , Heath Paul , Hood Kerry , Petrou Stavros , Stenson Ben , McMullen Sarah , Saunders Julia , Stanley Alison , Walters Stephen , Bossuyt Patrick , Gilbert Ruth , Hughes Rhona 
Published: January 2022

Abstract
Background
Mother-to-baby transmission of group B Streptococcus (GBS) is the main cause of early-onset infection. We evaluated whether, in women with clinical risk factors for early neonatal infection, the use of point-of-care rapid intrapartum test to detect maternal GBS colonisation reduces maternal antibiotic exposure compared with usual care, where antibiotics are administered due to those risk factors. We assessed the accuracy of the rapid test in diagnosing maternal GBS colonisation, against the reference standard of selective enrichment culture.

Methods
We undertook a parallel-group cluster randomised trial, with nested test accuracy study and microbiological sub-study. UK maternity units were randomised to a strategy of rapid test (GeneXpert GBS system, Cepheid) or usual care. Within units assigned to rapid testing, vaginal-rectal swabs were taken from women with risk factors for vertical GBS transmission in established term labour. The trial primary outcome was the proportion of women receiving intrapartum antibiotics to prevent neonatal early-onset GBS infection. The accuracy of the rapid test was compared against the standard of selective enrichment culture in diagnosing maternal GBS colonisation. Antibiotic resistance profiles were determined in paired maternal and infant samples.

Results
Twenty-two maternity units were randomised and 20 were recruited. A total of 722 mothers (749 babies) participated in rapid test units; 906 mothers (951 babies) were in usual care units. There was no evidence of a difference in the rates of intrapartum antibiotic prophylaxis (relative risk 1.16, 95% CI 0.83 to 1.64) between the rapid test (41%, 297/716) and usual care (36%, 328/906) units. No serious adverse events were reported. The sensitivity and specificity measures of the rapid test were 86% (95% CI 81 to 91%) and 89% (95% CI 85 to 92%), respectively. Babies born to mothers who carried antibiotic-resistant Escherichia coli were more likely to be colonised with antibiotic-resistant strains than those born to mothers with antibiotic-susceptible E. coli.

Conclusion
The use of intrapartum rapid test to diagnose maternal GBS colonisation did not reduce the rates of antibiotics administered for preventing neonatal early-onset GBS infection than usual care, although with considerable uncertainty. The accuracy of the rapid test is within acceptable limits.

Trial registration
ISRCTN74746075. Prospectively registered on 16 April 2015