Prevention of Group B streptococcal and other bacterial infections in newborns.
What is the best strategy to protect babies from the effects of their pregnant mothers carrying strep B?
Extension of current best practice to treat all women with preterm or high risk term deliveries is readily achievable and would be beneficial. The choice between adding culture testing for low risk women [that is, screening all pregnant women] or vaccination for all should be informed by further research.
A group of researchers based at ICH, York Centre for Health Economics and the MRC Health Services Research Unit if Bristol published a paper in the BMJ last week that should make a difference to how clinicians deal with group B streptococcal infection in pregnancy in the UK. Group B streptococcus is a bacterium that forms part of the normal vaginal bacterial flora in about 20% of women. The danger is that rarely, babies become infected with GBS during labour or delivery. Infection can result in rapid and devastating septicaemia or meningitis in the baby, which can be fatal.
The study was commissioned to inform UK policy makers deciding whether women should be screened for GBS during pregnancy, and if found to be positive, treated with intravenous antibiotics during labour. Screening is well established in many other developed countries but is not currently recommended in the UK because evidence is lacking about its effectiveness. A major disadvantage of screening for GBS is that a large proportion of women, 30 to 50% in the USA, end up being treated with intravenous antibiotics during labour.
The study involved a synthesis of all the available evidence on GBS and other bacterial infections transmitted from the mother to her baby during delivery and modelling to determine which strategy would be cost effective for the UK.
The study showed that current best practice is not cost effective. The authors concluded that immediate extension of practice to treat all preterm and high risk term deliveries would be beneficial and could be readily implemented. About 11% of women would be treated with antibiotics as a result. What should happen thereafter is more uncertain. One option would be culture-based testing for low risk women who deliver at term. However, within the next 5 to 10 years, it is expected that a GBS vaccine will be available. Vaccination for all women, combined with treatment of all preterm and high risk term deliveries without any testing, would be a more cost effective option.
These findings present policy makers with a dilemma. Should they adopt screening for low risk term deliveries now, knowing that the costs of setting up a comprehensive screening service would not be recouped if a vaccine, which is likely to be more cost effective without screening, becomes available in the next few years?
To assist policy makers, the study went on to perform a ‘value of information analysis’ to determine how much it would be worth investing in further research before deciding whether to implement screening or not. The authors found that further research would be cost effective and that trials to evaluate vaccine efficacy should be prioritised.
In summary, the study did not provide clear cut evidence, as the Group B Strep Support Group has claimed (http://www.scientificblogging.com/newswire/testing_women_for_group_b_strep_during_pregnancy_could_save_the_government_gbp37_million_a_year_says_new_research), that ‘offering testing for group B Strep carriage to all pregnant women is the most cost effective option, with antibiotics being offered in labour where GBS is found.’ Rather the study acknowledges considerable uncertainty about the best option and shows that it might be better to invest in research for a vaccine than to implement universal screening for low risk women.
The GBS support group also claimed that screening would save the government money. This is not true. The study compared all options against a baseline of doing nothing. However, clinicians are not ‘doing nothing’ at the moment. Current best practice involves treating some high risk women, but, according to the study, more women could benefit. The study is clear that current best practice is not effective and that treatment should be extended to include all women delivering preterm and those delivering at term who are defined as ‘high risk’.
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