What is the role of white blood count (WBC) testing in the workup of pertussis (whooping cough)?

Updated: May 02, 2019
  • Author: Joseph J Bocka, MD; Chief Editor: Russell W Steele, MD  more...
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Leukocytosis (15,000-50,000/µL) with absolute lymphocytosis occurs during the late catarrhal and paroxysmal phases. It is a nonspecific finding but correlates with the severity of the disease. One study showed that among infants suspected of having pertussis, an absolute leukocyte count lower than 9400/μL excluded almost all infants who had a negative pertussis test finding. [29] In adults, especially those who have been vaccinated, lymphocytosis is rare.

In infants aged 90 days or younger, early serial monitoring of white blood cell (WBC) counts is crucial for identifying risk and determining the prognosis of infants with pertussis. A retrospective study of 31 infants with pertussis found that WBC counts higher than 30,000/μL (within a mean of 5.1 days after cough onset), rapid heart rates, and hyperventilation were indicators of severe B pertussis infection. [30, 31]

In this study, WBC counts in infants with severe disease tended to elevate more rapidly than those in infants with less severe disease. [30, 31] Moreover, WBC counts reached higher peaks in patients with severe pertussis than in those with less severe pertussis (mean, 74,200/μL vs 26,900/μL; median, 74,100/μL vs 24,200/μL).

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