Monitor white blood cell count in pertussis infants

By Piriya Mahendra, medwireNews Reporter

Researchers say that taking early and repeat white blood cell (WBC) counts could help determine which children with pertussis are at highest risk for death.

James Cherry (University of California, Los Angeles, USA) and team report that an elevated and rapidly rising WBC count is a predictor for severe Bordetella pertussis, making early and serial WBC count determination vital for the evaluation of all infants with suspected or proven pertussis.

"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," commented co-author Erin Murray (California Department of Public Health, Richmond, USA) in a press statement.

"This study shows the importance of aggressive pediatric intensive care and provides us with additional metrics so we can treat these very young patients."

The analysis of 31 infants (mean age at cough onset 39.2 days) with pertussis admitted to pediatric intensive care units from September 2009 to June 2011 showed that eight had more severe B. pertussis infection, six had pulmonary hypertension, and four infants died. Two of the infants who died had pulmonary hypertension.

Infants with more severe B. pertussis infection (defined as death from pertussis or diagnosis of pulmonary hypertension) had significantly higher peak WBC counts, at a median of 74,100, than those with less severe disease, who had a mean count of 24,200.

All infants with more severe pertussis had a WBC count of 30,000 or more, compared with only 36% of those with less severe disease. Of infants with a WBC count of 30,000 or more, those with more severe pertussis reached or exceeded a count of 30,000 earlier in their illness course than those with less severe disease, at a mean of 5.1 days from cough onset to 22.2 days.

Of the infants who had more than one WBC count performed in a 24-hour period, those with more severe disease were significantly more likely to have at least a 50% increase in WBC count within 24 hours than patients with less severe disease, at 57% versus 0%. All but one infant with more severe infection had at least a 50% increase in WBC count within 48 hours.

As reported in the Journal of the Pediatric Infectious Diseases Society, none of the infants with less severe pertussis experienced over a 50% increase in WBC count within 48 hours.

Infants with more severe pertussis had a significantly higher maximum heart rate than those with less severe infections, at a mean of 210.8 versus 188.5. In addition, infants with more severe pertussis had a significantly higher maximum respiratory rate than infants with less severe infections, at a median of 97.5 versus 67.0.

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