The research, carried out by Consultant Obstetrician and Gynaecologist Dr Meave Eogan, found that among a cohort of 200 women 15-20 per cent carried GBS.
The study revealed that a proportion of women with risk factors for GBS were receiving antibiotics in labour but were not carriers at that time. There were also women not receiving antibiotics in labour who were carriers. During the course of the study, which was presented at the recent Rotunda Hospital Research Day, no babies became significantly unwell due to GBS.
“There were a number of babies who were receiving septic screens after they were delivered whose mother’s didn’t have group B strep. So the babies were being intensively monitored after birth when they weren’t really at risk,” Dr Eogan said.
The PCR test used was the GeneXpert GBS test manufactured by Cepheid. It claims to produce positive results in 32 minutes with negative results in under an hour. It boosts sensitivity of 91.9 per cent and specificity of 95.6 per cent. Dr Eogan said they compared the test to gold standard lab cultures and found it to be accurate.
The next step was to expand the study and explore the cost-effectiveness of the approach, she said. While it costs about €40 per person, the PCR test could potentially reduce antibiotic use and interventions in newborns. In countries where universal screening was offered between 35 and 37 weeks gestation, the rapid test has been deemed cost-effective, she added.
While universal screening is recommended in the US, Australia and many European countries, Ireland and the UK have taken a risk-based approach to date. Having a previous baby affected by GBS, preterm labour, waters being broken for more than 18 hours and a high temperature during labour are among the risk factors for infection.
Dr Eogan said that while there had long been discussion about introducing universal screening in Ireland, it was introduced in the US because it traditionally had a higher incidence of GBS. “The US has brought down its incidence of invasive group B strep disease to 0.4 per 1,000, which is really in or around our steady state,” she said.
Dr Eogan added that the problem with screening at 35-37 weeks gestation was that carriage of GBS could be dynamic. Women can be falsely reassured by a negative screen at 35 weeks, but be carriers at the onset of labour. On the other hand, women who screen positive at 35 weeks can be “terribly nervous for the last five weeks” but not carry it at the time of labour.
“We can now use PCR, which means we can screen women at the onset of labour and make real-time decisions for them, and this will better enable us to triage people for antibiotics in labour. It probably won’t change the number of people who get antibiotics but… you would hope it would make sure that the people who get antibiotics are the people who really need them,” she said.
Figures from the Rotunda over the past 13 years showed that less than 1-in-1,000 babies became significantly unwell as a result of GBS.
Dr Eogan said it affected between 30 and 60 babies in Ireland a year among approximately 65,000 births.
However, the literature showed that of those who became significantly unwell, the mortality rate was as high as 10 per cent.