Bordetella pertussis is the highly contagious etiological agent of pertussis (a.k.a., whooping cough). According to the Centers for Disease Control and Prevention (CDC), in the 20th century, pertussis was one of the most common childhood diseases. Before the availability of the pertussis vaccine in the 1940s, more than 200,000 cases of pertussis were reported annually. Since widespread use of the vaccine began, incidence has decreased more than 75% compared with the pre-vaccine era. However, since the 1980s, there has been an increase in the number of reported cases of pertussis. In 2012, the last peak year, 48,277 cases of pertussis were reported.
While there are several types of laboratory tests used for B. pertussis, including polymerase chain reaction (PCR), serology, culture, and direct fluorescent antibody (DFA) testing, the CDC recommends PCR testing for patients suspected of having acute pertussis. Mayo Medical Laboratories offers a PCR assay for B. pertussis.
For quality control purposes, Mayo Medical Laboratories (MML) monitors the positivity rates of its PCR assays. In a recent issue of the Journal of the Pediatric Infectious Diseases Society, Mayo Clinic researchers report on an eight-year review of B. pertussis testing that revealed jointed testing patterns compared to positivity rates.
The review, conducted from 2007 to 2014, and aided by quality specialists, Stefanea Rucinski and Senait Gebrehiwot, revealed a yearly spike in positivity rates during the summer months throughout the United States, even though the highest test volumes occurred outside of this time frame. Early on, the apparent variation in the positivity rate of MML’s assay over time was a concern to the researchers, since it called into question the assay’s performance accuracy and quality to clinicians.
“When we initially observed differences in positivity rates at different times of the year, we had to make sure that our assay was performing properly, which it was. Then, we thought this information might be of interest to clinicians ordering testing for pertussis, especially because the highest test volumes seemed to occur outside of the peak times of positivity. The seasonality of pertussis, which is not intuitive, was also apparently not commonly appreciated by clinicians,” said Robin Patel, M.D., Chair of the Division of Clinical Microbiology at Mayo Clinic and first author on this review.
These findings indicate that, although pertussis can occur anytime, clinicians should be aware that positivity rates are typically highest in the summer.
“For easy reference, we have coined the term, ‘summertime cough,’ to indicate when B. pertussis has its highest positivity rates,” said Dr. Patel.
Mayo Medical Laboratories has an online tool called “MicrobeWatch” for Mayo clinicians located in Rochester, Minn., to check current positivity rates for pertussis (along with influenza, respiratory syncytial virus, and Streptococcus pyogenes). The tool provides real-time, up-to-date data.
For more information about Bordetella pertussis, view Mayo Medical Laboratories’ test offering, a Hot Topic video on testing for Bordetella pertussis, and a Utilization Spotlight on laboratory testing for pertussis.