PCR, Culture and Serology as Diagnostic Tools for Pertussis in Highly-Vaccinated Children

1. PCR, Culture and Serology as Diagnostic Tools for Pertussis in Highly-Vaccinated Children E. Bamberger, M. Jaffe, R. Gershtein, D. Benilevi, I. Srugo B’nai Zion Medical Center N. Lahat, V. Gershtein, S. Shapiro Carmel Medical Center I. Kassis Rambam Medical Center

2. Incidence of B. Pertussis in Israel: 1967-2001 (Source: ICDC)

3. Bordetella pertussis:Changing Manifestation &Epidemiology • Pre-vaccine era: Classical disease • Current, vaccine era: Disease more protracted; “Atypical” • The incidence of pertussis shows two groups at increased risk: • Infants younger than 6 months • Teenagers and adults

4. Reemergence of B. pertussis Atypical clinical disease Increased reservoir for transmission Increased incidence Limitations of lab techniques Waning immunity

5. PCR Amplifies a Targeted Sequence Target Sequence DNA Strand Double Helix DNA Strand Supercoiled DNA Strand Chromosome

6. Target Amplification No. of No. Amplicon Cycles Copies of Target 1 2 2 4 3 8 4 16 5 32 6 64 20 1,048,576 30 1,073,741,824 1 cycle = 2 Amplicon 2 cycle = 4 Amplicon 3 cycle = 8 Amplicon 4 cycle = 16 Amplicon 5 cycle = 32 Amplicon 6 cycle = 64 Amplicon 7 cycle = 128 Amplicon

7. PCR Laboratory Diagnosis Clinically validated, semi-nested PCR based on rapid insertion sequence • Specificity = 96%. • Sensitivity = 99%

8. Objectives • To compare clinical & laboratory diagnostic methods used in the diagnosis of B. pertussis • To examine whether child’s immunization status matters? • To examine utility of CDC diagnostic criteria?

9. Materials and Methods • Clinical symptomotology and immunization status were collected for 306 patients with suspected pertussis between 1999 - 2000 • Two nasopharyngeal swabs were collected for PCR and culture. • Serum specimen for IgM and IgA Bordetella pertussis serology

10. Pre-vaccinated infants </=1 yr (0-1 doses) (n=87) Recently vaccinated children <5 yrs (3-4 doses) or </=1 yr (2 doses) (n=78) Post-vaccinated children 5-18 yrs (4 doses) (n=75) Stratification of Sample (n=240)

11. Demographic Profile of Sample

12. Laboratory Profile of Sample

14. Odds Ratios for Clinical Predictors of Positive PCR (By Group) *p<.10; **p<.05; ***p<.001

15. Association Between PCR and Cough Among Pre-vaccinated Subjects

16. Case definition for pertussis (CDC) Clinical case of pertussis is defined as a cough illness lasting at least 2 weeks with either: • paroxysms of cough • inspiratory whoop • post-tussive vomiting without other apparent cause

17. 3 : Figure Percent of Missed Pertussis Diagnosis Using CDC Confirmed Criteria 76 76 . . 09 09 80 80 70 70 57 57 . . 45 45 60 60 50 50 40 40 38 38 . . 39 39 40 40 30 30 20 20 10 10 0 0 Pre Pre - - Recently Recently Post Post - - Full Sample Population vaccinated vaccinated vaccinated vaccinated vaccinated vaccinated Percent of Missed Diagnosis of Pertussis Applying CDC Criteria

18. Conclusion (1) • PCR is a useful tool for pertussis diagnosis, particularly in pre-vaccinated infants • The yield of culture and serology is limited, especially among pre-and recently vaccinated children.

19. Conclusion (2) • As recently- and post-vaccinated children often exhibit atypical disease, many may go undiagnosed, thus increasing the reservoir for transmission • In pre-vaccinated infants with whoop and <2 weeks of cough, PCR should be preformed promptly • In Israel, the adoption of a 5th booster dose should be strongly considered