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Issues associated with and recommendations for using PCR to detect outbreaks of pertussis
Fabio A Lievano1, Meredith A Reynolds, Alfred L Waring
1Epidemic Intelligence Service, Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. flievano@cdc.gov
Abstract:
Two outbreaks of respiratory tract illness associated with prolonged cough occurring in 1998 and 1999 in New York State were investigated. A PCR test for Bordetella pertussis was primarily used by a private laboratory to confirm 680 pertussis cases. Several clinical specimens had positive culture results for B. pertussis during both outbreaks, which confirmed that B. pertussis was circulating during the outbreaks. However, testing by the New York State Department of Health reference laboratory suggested that some of the PCR results may have been falsely positive. In addition, features of the outbreak that suggested that B. pertussis may not have been the primary agent of infection included a low attack rate among incompletely vaccinated children and a significant amount of illness among patients testing PCR negative for B. pertussis. These investigations highlight the importance of appropriate clinical laboratory quality assurance programs, of the limitations of the PCR test, and of interpreting laboratory results in context of clinical disease.
Insights
Bordetella pertussis outbreaks were investigated, but PCR testing limitations and clinical features suggested it may not have been the primary cause of illness. Laboratory quality assurance is crucial for accurate diagnosis.
Area of Science:
- Epidemiology
- Infectious Diseases
- Clinical Microbiology
Background:
- Two outbreaks of respiratory illness with prolonged cough occurred in New York State in 1998-1999.
- Bordetella pertussis (pertussis) was initially suspected as the causative agent based on PCR testing.
Purpose of the Study:
- To investigate the etiology of two respiratory illness outbreaks.
- To evaluate the accuracy of PCR testing for Bordetella pertussis in outbreak settings.
Main Methods:
- Investigation of two outbreaks of respiratory tract illness.
- Confirmation of Bordetella pertussis using PCR and culture.
- Analysis of clinical data, vaccination status, and laboratory results.
Main Results:
- 680 pertussis cases were reported, with B. pertussis confirmed by culture in some specimens.
- Reference laboratory testing suggested potential false-positive PCR results.
- Low attack rates in vaccinated children and illness in PCR-negative patients raised questions about B. pertussis as the primary agent.
Conclusions:
- The study highlights the importance of clinical laboratory quality assurance programs.
- Limitations of PCR testing for Bordetella pertussis were identified.
- Interpreting laboratory results within the clinical context is essential for accurate diagnosis.