THURSDAY, Jan. 10 (HealthDay News) -- Taking early and repeated white blood cell counts is vital in diagnosing whooping cough (pertussis) in infants and identifying which of them have the highest risk of dying from the respiratory infection, according to a new study.
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Researchers examined the medical records of 31 infants admitted to five pediatric intensive-care units in California between September 2009 and June 2011. In 2010, California had its highest pertussis rate in 60 years.
The study, which was published online Jan. 10 and in the March print issue of the Journal of the Pediatric Infectious Diseases Society, found that the eight infants with more severe pertussis had higher white blood cell counts and were more likely to show at least a 50 percent increase in white blood cells. They had median peak white blood cell counts of about 74,000, compared with about 24,000 among infants with less severe pertussis.
All but one infant with more severe pertussis had at least a 50 percent increase in white blood cells within 48 hours, while none of the infants with less severe pertussis had more than a 50 percent increase in white blood cells.
The researchers also found that the infants with more severe pertussis had higher maximum heart and breathing rates and were more likely to develop pneumonia. These conditions occurred earlier in infants with more severe pertussis than in those with less severe disease.
In addition, infants with more severe pertussis were more likely to suffer seizures, shock and kidney failure, and to require a breathing tube. They also were more likely to receive an exchange blood transfusion, in which most of the blood is replaced with fresh blood.
Six of the infants received exchange transfusions, and four of them died. The four who died were in shock at the time of the transfusion, while the two who survived were not in shock.
"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," study lead author Erin Murray, an epidemiologist at the California Department of Public Health, said in a journal news release.
"This study shows the importance of aggressive pediatric intensive care and provides us additional metrics as we treat these very young patients," Murray added.
In 2012, pertussis rates in the United States were the highest in 50 years, according to the U.S. Centers for Disease Control and Prevention.
-- Robert Preidt
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SOURCE: Journal of the Pediatric Infectious Diseases Society, news release, Jan. 10, 2013