Objective
The purpose of this study was to compare adherence to the 2002 Centers for Disease Control (CDC) guidelines for the prevention of perinatal group B Streptococcus (GBS) disease in patients who are allergic to penicillin during the years 2004-2006 and 2008.
Study Design
Previous data from our institution revealed suboptimal adherence to the 2002 CDC guidelines for GBS prophylaxis among women who are allergic to penicillin. These data caused the hospital to implement a series of interventions. The original cohort (2004-2006) was compared with a cohort of women who delivered between April 2008 and January 2009 (n = 74) to determine whether the proportion of women who had antimicrobial sensitivity testing and who had received an appropriate antibiotic had improved.
Results
In 2008, 76% (95% confidence interval, 66–84%) of GBS-positive women who are allergic to penicillin received an appropriate antibiotic (compared with 16.2% in 2004-2006; P < .001). Antimicrobial sensitivity testing was performed in 79.4% of cases (95% confidence interval, 68–87%), compared with 11.4% in 2004-2006 ( P < .001).
Conclusion
With directed intervention, adherence to the 2002 CDC guidelines for GBS prophylaxis in women who are allergic to penicillin improved dramatically.
Group B Streptococcus (GBS) is a leading cause of neonatal infection; intrapartum prophylactic antibiotics have reduced the incidence of early-onset neonatal GBS disease by 70%. Penicillin is the recommended antibiotic for GBS prophylaxis; historically, patients who have reported a penicillin allergy received either clindamycin or erythromycin. Given the increasing prevalence of GBS resistance to both clindamycin and erythromycin, the Centers for Disease Control (CDC), in collaboration with the American College of Obstetricians and Gynecologists and the American Association for Pediatrics, provided new guidelines for the prevention of early-onset neonatal GBS disease in 2002 that included specific guidelines for patients with a reported penicillin allergy.
In 2007, we published the results of our study that evaluated adherence to the 2002 CDC GBS prophylaxis guidelines for women who were GBS-positive and allergic to penicillin who delivered at Women and Infants Hospital (WIH) between 2004 and 2006. We found suboptimal adherence, with only 11% of patients who were GBS-positive and allergic to penicillin undergoing sensitivity testing and 16% receiving an appropriate antibiotic based on the 2002 CDC recommendations. In response to these findings, WIH instituted a series of interventions that were aimed to improve adherence to the guidelines. These interventions included educating providers by presenting lectures on the guidelines (hospital research presentation, staff meetings, and Grand Rounds) and highlighting the 2002 CDC guidelines for GBS prophylaxis as “guideline of the month” (where details of the guidelines were provided on posters throughout the hospital). In addition, a field for “penicillin allergy” was added to laboratory ordering systems so that, if filled out properly, the laboratory could be prompted reflexively to perform GBS sensitivity testing.
The aim of the current study was to evaluate whether adherence to the 2002 CDC guidelines for GBS prophylaxis has improved since the 2004-2006 data collection period. We hypothesized that, among patients who were allergic to penicillin and GBS-positive who delivered at WIH between April 2008 and January 2009, both the proportion of patients who received antimicrobial sensitivity testing and the proportion who received an appropriate antibiotic increased from the previous 2004-2006 data collection period.
Materials and Methods
We performed a retrospective cohort study of obstetric patients who were GBS-positive and reported a penicillin allergy and who delivered at WIH between April 1, 2008, and January 1, 2009. April 1, 2008, was chosen because WIH implemented its interventions that were aimed to improve adherence to the guidelines between May 2007 and March 2008. WIH institutional review board approval for this project was obtained in December 2007.
To select the study sample, a list of all patients who were GBS-positive who delivered between April 1, 2008, and January 1, 2009, was generated with the use of International Classification of Diseases–9th revision codes 648.91 and v02.51. The electronic medical records of each patient who was GBS-positive (n = 1221) was reviewed by the research team to identify those patients who also reported a penicillin or penicillin-derivative allergy (n = 104; Figure 1 ).
Data were abstracted from medical records onto standardized data collection forms by the principal investigator and a trained research assistant. We recorded data on age, obstetric provider, insurance status, gestational age at delivery, type of delivery, recorded nature of the penicillin allergy, means of identifying GBS positivity, antimicrobial sensitivity testing, and antibiotics received. Selection of the study sample was verified for accuracy first by having 10% of the medical records of patients who were GBS-positive reviewed by 2 members of the research team to confirm penicillin allergy; no discrepancies were identified. Additionally, we used a system of double data entry for all abstracted charts; discrepancies were reconciled by rereviewing the data collection sheets before data analysis. All data were maintained in a confidential computerized database.
We described the age, gravidity, parity, race/ethnicity, provider type, type of insurance, gestational age at delivery, mode of delivery, means in which GBS positivity was determined, whether the nature of the penicillin allergy was documented, and antibiotic administered for our population of patients who were GBS-positive penicillin-allergic (n = 104). We then compared, in this population, (1) patients who received antimicrobial sensitivity testing with those who did not and (2) patients who received an appropriate antibiotic with those who did not. For both of these analyses, we excluded women who had a gestational age <37 weeks (n = 10) and women who had a cesarean delivery without labor who were at a gestational age of >37 weeks (n = 9). We excluded women who delivered at <37 weeks of gestation because the women are not universally screened for GBS . Women with a cesarean delivery without labor were excluded because these patients do not universally require GBS prophylaxis.
Antimicrobial sensitivity testing was defined as “performed” if it was documented in the antenatal records, in the laboratory data sheets, in the intrapartum chart, in the postpartum chart, or in the electronic laboratory data files. Women who received a cephalosporin who were determined to be at low risk for anaphylaxis (n = 17) were excluded for the analyses of antimicrobial sensitivity testing, because antimicrobial sensitivity testing is not uniformly necessary for patients who are at low risk for anaphylaxis. The final sample size for these analyses was 68 women.
Appropriate antibiotic was defined as cephalosporin for patients who were at low risk for anaphylaxis, clindamycin, or erythromycin if GBS was susceptible to both of these antibiotics and as vancomycin if antimicrobial sensitivity was unknown or if GBS was resistant to either clindamycin or erythromycin. One patient who had missing data on the outcome (antibiotic administered) was excluded from the analyses of appropriate antibiotic administration. The final sample size for these analyses was 84 women.
We performed a sample size calculation for both of our primary outcomes (proportion of patients who received antimicrobial sensitivity testing and proportion who received an appropriate antibiotic). From our previous study, we knew that 11% of women who were GBS-positive and penicillin-allergic received antimicrobial sensitivity testing and that 16% of the women received an appropriate antibiotic. To determine at least a 20% increase in both of these outcomes and to set an α of .05 and a β of .20, we needed 53 women for analyses of antimicrobial sensitivity testing and 68 women for analyses of appropriate antibiotic administration. Data were analyzed with Stata software (version 9.0; Stata Corporation, College Station, TX). Categoric variables were compared with the use of the Fisher’s exact test; medians were compared with the Wilcoxon’s rank sum test, and 95% confidence intervals (CIs) were calculated for binomial proportions with the Agresti-Coull method.
Results
Between April 1, 2008, and December 31, 2008, there were 6982 deliveries at WIH. Of those, 1221 patients who were GBS-positive were identified, giving a 17.5% prevalence of GBS positivity. Approximately 9% of these women (n = 104) reported a penicillin allergy; these charts were reviewed.
In this population, 75% of women had documentation of the nature of their penicillin allergy, and 76% of women delivered vaginally ( Table 1 ). Overall, 94% of women received antibiotic prophylaxis; 47% of these women were given clindamycin. After the detailed exclusion and inclusion criteria were applied to the sample, 85 patients remained, and their charts were eligible for analyses ( Figure 1 ).
| Characteristic | n a | Column % a , b (95% CI) |
|---|---|---|
| Race/ethnicity | ||
| White, non-Hispanic | 74 | 71.2 (61.8–79.0) |
| Black, non-Hispanic | 10 | 9.6 (5.1–17.0) |
| Hispanic | 12 | 11.5 (6.6–19.2) |
| Other | 5 | 4.8 (1.8–11.0) |
| Unknown | 3 | 2.9 (0.6–8.5) |
| Gestational age at delivery, wk | ||
| <37 | 10 | 9.6 (5.1–17) |
| ≥37 | 94 | 90.4 (83.0–94.9) |
| Age, y c | 29 | 13–41 |
| Gravidity | 2 | 1–9 |
| Parity | 1 | 0–4 |
| Type of delivery | ||
| Vaginal | 79 | 76.0 (66.9–83.2) |
| Cesarean after labor | 14 | 13.5 (8.1–21.5) |
| Cesarean without labor | 11 | 10.6 (5.8–18.1) |
| Method of identification GBS + | ||
| Rectovaginal culture | 73 | 70.2 (60.8–78.2) |
| GBS bacteruria | 14 | 13.5 (8.1–21.5) |
| Screening method not documented | 17 | 16.4 (10.4–24.7) |
| Nature of penicillin allergy documented in medical record | 78 | 75.0 (66.6–83.5) |
| Received intrapartum antibiotics | 98 | 94.2 (87.7–97.6) |
| Type of antibiotics received | ||
| Cephalosporin | 22 | 22.5 (15.3–31.7) |
| Clindamycin | 46 | 46.9 (37.4–56.7) |
| Erythromycin | 2 | 2.0 (0.1–7.6) |
| Vancomycin d | 28 | 28.6 (20.5–38.2) |
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