Background: Mother-to-baby transmission of group B Streptococcus (Streptococcus agalactiae) is the main cause of early-onset infection.
Objectives: We investigated if intrapartum antibiotic prophylaxis directed by a rapid intrapartum test reduces maternal and neonatal antibiotic use, compared with usual care (i.e. risk factor-directed antibiotics), among women with risk factors for vertical group B Streptococcus transmission, and examined the accuracy and cost-effectiveness of the rapid test.
Design: An unblinded cluster randomised controlled trial with a nested test accuracy study, an economic evaluation and a microbiology substudy.
Setting: UK maternity units were randomised to either a strategy of rapid test or usual care.
Participants: Vaginal and rectal swabs were taken from women with risk factors for vertical group B Streptococcus transmission in established term labour. The accuracy of the GeneXpert® Dx IV GBS rapid testing system (Cepheid, Maurens-Scopont, France) was compared with the standard of selective enrichment culture in diagnosing maternal group B Streptococcus colonisation.
Main outcome measures: Primary outcomes were rates of intrapartum antibiotic prophylaxis administered to prevent early-onset group B Streptococcus infection and accuracy estimates of the rapid test. Secondary outcomes were maternal antibiotics for any indication, neonatal antibiotic exposure, maternal antibiotic duration, neonatal group B Streptococcus colonisation, maternal and neonatal antibiotic resistance, neonatal morbidity and mortality, and cost-effectiveness of the strategies.
Results: Twenty-two maternity units were randomised and 20 were recruited. A total of 722 mothers (749 babies) participated in rapid test units and 906 mothers (951 babies) participated in usual-care units. There were no differences in the rates of intrapartum antibiotic prophylaxis for preventing early-onset group B Streptococcus infection in the rapid test units (41%, 297/716) compared with the usual-care units (36%, 328/906) (risk ratio 1.16, 95% confidence interval 0.83 to 1.64). There were no differences between the groups in intrapartum antibiotic administration for any indication (risk ratio 0.99, 95% confidence interval 0.81 to 1.21). Babies born in the rapid test units were 29% less likely to receive antibiotics (risk ratio 0.71, 95% confidence interval 0.54 to 0.95) than those born in usual-care units. The sensitivity and specificity of the rapid test were 86% (95% confidence interval 81% to 91%) and 89% (95% confidence interval 85% to 92%), respectively. In 14% of women (99/710), the rapid test was invalid or the machine failed to provide a result. In the economic analysis, the rapid test was shown to be both less effective and more costly and, therefore, dominated by usual care. Sensitivity analysis indicated potential lower costs for the rapid test strategy when neonatal costs were included. No serious adverse events were reported.
Conclusions: The Group B Streptococcus 2 (GBS2) trial found no evidence that the rapid test reduces the rates of intrapartum antibiotic prophylaxis administered to prevent early-onset group B Streptococcus infection. The rapid test has the potential to reduce neonatal exposure to antibiotics, but economically is dominated by usual care. The accuracy of the test is within acceptable limits.
Future work: The role of routine testing for prevention of neonatal infection requires evaluation in a randomised controlled trial.
Trial registration: Current Controlled Trials ISRCTN74746075.
Funding: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 12. See the NIHR Journals Library website for further project information.
Keywords: ACCURACY; ANTIBIOTICS; COLONISATION; GROUP B STREPTOCOCCUS; HEALTH ECONOMICS; LABOUR; PREGNANCY; RANDOMISED CONTROLLED TRIAL.
What is the problem?: Group B Streptococcus is a common bacterium found in the vagina and intestines of approximately one in four women. Group B Streptococcus may be passed to the baby around birth and cause severe infection. In the UK, women are offered antibiotics in labour to protect their baby from group B Streptococcus infection when specific risk factors are present. Most women with risk factors do not carry group B Streptococcus and their babies are unnecessarily exposed to antibiotics. Most women carrying group B Streptococcus do not have risk factors and so will not be offered antibiotics to protect their babies.
What did we plan to do?: We planned to find out if, for women with risk factors, a ‘rapid test’ in labour resulted in fewer women receiving antibiotics compared with ‘usual care’. We also wanted to establish if the test correctly identified if mothers were carrying group B Streptococcus, helped reduce infections in babies and represented value for money.
What did we find?: We involved 1627 women (1700 babies) from 20 hospitals randomly allocated to rapid test or usual care. Using the ‘rapid test’ did not reduce antibiotics provided to mothers (41% in rapid test units and 36% in usual-care units). The test correctly identified 86% of women carrying group B Streptococcus, 89% of those who did not and failed to provide a result in 14% of women. A rapid test policy resulted in 13% fewer babies receiving antibiotics. The rapid test generated no cost savings when only the mothers’ care was considered, but there was potential for reduced costs when including the newborns’ hospital stay.
What does this mean?: The rapid test is accurate; however, using it for women with risk factors for their baby developing group B Streptococcus infection does not reduce antibiotic usage in mothers, although it does in babies. Value for money is uncertain and depends on what costs are included.