Prenatal screening and treatment strategies to prevent group B streptococcal and other bacterial infections in early infancy: cost-effectiveness and expected value of information analyses.
OBJECTIVE
To determine the cost-effectiveness of prenatal strategies for preventing group B streptococci (GBS) and other serious bacterial infections in early infancy and to establish the expected value of further information.


METHODS
Electronic databases were searched up to March 2006. Expert opinion was also sought.


METHODS
Twelve mutually exclusive maternal risk groups were defined at presentation in labour and the consequences considered of early-onset GBS and non-GBS bacterial infections and late onset GBS infection, measured in terms of lifetime NHS costs and quality-adjusted life-years (QALYs). These were for preterm delivery (<37 weeks): (1) planned Caesarean section, (2) previous baby with GBS disease, (3) positive urine or vaginal swab for GBS in current pregnancy, (4) fever >or=38 degrees C during labour, (5) membrane rupture >or=2 hours before labour onset, (6) membrane rupture <2 hours before labour onset. For term delivery (>or=37 weeks): (7) planned Caesarean section, (8) previous baby with GBS disease, (9) positive urine or vaginal swab for GBS in current pregnancy, (10) fever >or=38 degrees C during labour, (11) membrane rupture >or=18 hours, and (12) none of the above risk factors. Fourteen intervention strategies were applied to each maternal risk group. Data inputs were obtained from systematic reviews, primary data and expert opinion. The model parameters were simultaneously estimated from the data inputs using Bayesian evidence synthesis. The expected net benefit was calculated relative to no intervention for each intervention within each risk group for two scenarios, with and without vaccination. Interventions with more than a 1% probability of being cost-effective (i.e. maximising net benefit at a threshold of 25,000 pounds per QALY gained) in a specific risk group were combined to form strategies. To limit antibiotic exposure, women who were low risk at presentation could not be treated without a positive culture or polymerase chain reaction result.


RESULTS
Current best practice, comprising intravenous treatment for pyrexia, previous GBS baby and previous GBS swab or urine culture, and oral treatment for preterm pre-labour membrane rupture (groups 2-5 and 8-10) was not cost-effective. All cost-effective options involved treatment of all preterm groups and high-risk term groups (groups 8-10). Testing high-risk women for maternal GBS colonisation would not be cost-effective, as even those with negative results would be better off treated to reduce the risk of early-onset non-GBS infection. In the absence of vaccination, culture-based testing of women in groups 11 and 12, combined with treatment for the rest, would be the most cost-effective strategy. If vaccination was available, vaccination for all and treatment for groups 1-10 would be marginally more cost-effective than treatment for groups 1-10 and culture for groups 11 and 12, but this is uncertain and is based on expert opinion on vaccine efficacy. The expected value of perfect information results suggest that moderate investment in research would be worthwhile.


CONCLUSIONS
Based on our findings, immediate extension of current practice to treat all preterm and high-risk term groups would be beneficial. Further research aimed at the realisation of a GBS vaccine should be prioritized.
Colbourn
T
T
Centre for Paediatric Epidemiology and Biostatistics, UCL Institute of Child Health, London, UK.
Asseburg
C
C
Bojke
L
L
Philips
Z
Z
Claxton
K
K
Ades
A E
AE
Gilbert
R E
RE
D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001424:Bacterial Infections / Q000188:drug therapy / Q000209:etiology / Q000517:prevention & control*; D003362:Cost-Benefit Analysis; D016208:Databases, Factual; D036861:Delivery, Obstetric / Q000706:statistics & numerical data*; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D011296:Prenatal Diagnosis / Q000191:economics / Q000379:methods*; D019057:Quality-Adjusted Life Years; D012307:Risk Factors; D050497:Stillbirth; D013290:Streptococcal Infections / Q000188:drug therapy / Q000209:etiology / Q000517:prevention & control*; D013292:Streptococcus agalactiae
D000900:Anti-Bacterial Agents