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Department of Family Practice Journal Club

A Population-Based Comparison of Strategies to Prevent Early-Onset Group B Streptococcal Disease in Neonates . Schrag, S.J.; Zell, E.R.; Lynfield, R.; Roome, A.; Arnold, K.E., Craig, A.S.; Harrison, L.H.; Reingold, A.; Stefonek, K.; Smith, G.; Gamble, M. and Schuchat, A. for the Active Bacterial Core Surveillance Team. New England Journal of Medicine, Volume 347/4 (July, 25, 2002): 233-239..

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Department of Family Practice Journal Club

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    1. Department of Family Practice Journal Club Theresa A. Allison, M.D. September 4, 2002

    3. Background 1996 ACOG, AAP and CDC guidelines for intrapartum Group B Strep (GBS) prophylaxis recommend either : Risk based treatment, or Routine screening at 35-37 weeks Note that, as of March, 2002, the CDC is revising their recommendations.

    4. Risk-based treatment Clinical Group B Streptococcal risk factors: Prior history of infant with GBS sepsis Intrapartum fever (>38 degrees C) Prolonged (>18 hours) rupture of membranes Preterm delivery (<37 weeks GA) GBS bacteriuria

    5. Routine screening Looks for GBS colonization in all women, regardless of risk factors Vaginal/Rectal swab cultures obtained between 35 and 37 weeks

    6. Study Design Multistate, retrospective, cohort study Comparison of screening approach to early-onset GBS sepsis prevention versus risk-based approach Univariate and multivariate models used to determine relative risk in screened group relative to risk-based group

    7. Validity

    8. Population Stratified, random sample of 629,912 live births (1998-9) Eight geographical areas 5,144 births (sample size) 312 neonates with GBS sepsis (all cases)

    9. Weighting of cases Statistical weight assigned to each birth Weight = 1/probability of selection Early-onset invasive GBS infection, weight=1 Nonresponse (i.e. chart unavailable) assumed weight was representative of stratum Wieghting to adjust for birth hospital, surveillance area and year Further adjusted to reflect incidence of preterm births in overall population

    10. Data Collection Abstraction from L&D records Demographics of mother Screening for GBS Clinical risk factors Intrapartum antibiotic use Gestational age of infant (Birth registry data) Abstracters blinded to infection status of infants

    11. Analysis Relative risk for the infant of acquiring early-onset invasive GBS infection. Comparison of screening approach versus risk-based approach. Dependent variable: disease status of infant. Independent variables: screening, risk factors, potential confounders.

    12. Further analysis All women not screened were initially included in the risk-based group, RR= 0.46 (0.36-0.60). In order to adjust for women whose providers may have had no GBS prevention strategy, the authors then excluded the 207 patients who had risk factors but did not receive antibiotics. Adjusted RR=0.48 (0.37-0.61).

    13. Results

    14. Efficacy Efficacy (1-relative risk) assessed using antibiotic prophylaxis as independent variable. Among screened women with no risk factors, the efficacy of antibiotics in preventing infection was 88.6% (66.4-96.1%). Projected comparison of perfect implementation of risk-based approach suggests an absolute risk reduction from 0.5 per 1000 to 0.44 per 1000 live births. Study showed absolute risk for screened patients of 0.32 per 1000.

    15. Conclusions Routine screening for Group B streptococcus during pregnancy prevents more cases of early-onset disease than the risk-based approach (Schrag et al, 2002:233). Screening reduced by 54% (40-64% within 95% confidence interval) the incidence of early-onset GBS in the multivariate analysis.

    16. Conclusions Protective effect stems from: Identification of risk factor-free GBS carriers (18% of women in the screened group). The fact that this cohort was more likely to receive antibiotics (89% vs 50-79% for different clinical risk factors).

    17. Implication for Our Practice SFGH currently uses a risk-based approach with Penicillin G intrapartum prophylaxis. Should we switch to a screening approach?

    18. Changes in pathogens causing early-onset sepsis in very-low-birth-weight infants. Stoll BJ, Hansen N, Fanaroff AA, et al. New England Journal of Medicine 2002;347:240-7.

    19. Demographics

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