White blood cell counts key to pertussis prognosis

Taking early and repeated white blood cell counts is critical in determining whether infants have pertussis and which infants with pertussis are at highest risk of death from the disease.

Researchers examined medical records from five Southern California pediatric ICUs between September 2009 and June 2011. Of the 31 infants studied, eight comprised a group considered to have more severe infections, which included suffering from pulmonary hypertension and death from pertussis.

According to the data, infants who had more severe disease had higher white blood cell counts and were more likely to show at least a 50% increase in WBC. Infants with more severe disease had median peak WBC counts of 74,100 compared with 24,200 among infants with less severe disease. All but one of those with more severe disease had at least a 50% increase in WBC within 48 hours, while none of the infants with less severe disease had more than a 50% increase in WBC.

Additionally, the infants with more severe infections had higher maximum heart and respiratory rates on average and were more likely to develop pneumonia. These conditions occurred earlier after illness onset among infants with more severe disease.

This group also was more likely to have seizures, hypotension/shock and renal failure, and was more likely to be intubated and receive exchange transfusions. Six of the infants received exchange transfusions, and four of those died. Those four all were in shock at the time of their transfusions; the two who survived were not in shock at the time of transfusion.

Most children are vaccinated against pertussis at an early age, but infants are too young to complete the vaccination series. The U.S. Centers for Disease Control and Prevention reported that 2012 rates of the disease were the highest in 50 years, and some states are reporting case counts not seen since the 1930s, which was before the vaccine era.

“Because very young infants have not yet been vaccinated and are at the highest risk for severe disease, we need to better manage and treat it,” Erin Murray, PhD, the study¬ís lead author and an epidemiologist at the California Department of Public Health, said in a news release. “This study shows the importance of aggressive pediatric intensive care and provides us additional metrics as we treat these very young patients.”

The study is scheduled for publication in the Journal of the Pediatric Infectious Diseases Society. The study abstract is available at http://jpids.oxfordjournals.org/content/early/2013/01/04/jpids.pis105.abstract.

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