This article is more than 5 years old. Information may no longer be current.
Improper WBC differential unreliable for detecting meningococcal disease
Click Here to Manage Email Alerts
Automated methods that do not measure immature white blood cell counts should be avoided when assessing febrile children for meningococcal infection, according to recent study findings published in The Pediatric Infectious Disease Journal.
“Automated blood cell counts that do not measure bands will frequently be falsely reassuring in children with invasive meningococcal disease,” researchers wrote. Band counts allow “determination of [absolute neutrophil count], [immature neutrophil count], and [immature-to-total neutrophil ratio], which together are useful whenever blood cell counts are ordered for assessment of children with fever, to aid in the early identification of invasive bacterial infections including meningococcal disease.”
The study included 216 patients aged 1 month to 20 years (60.6% were aged younger than 4 years) using a data set previously collected from 2001 to 2011 by the US Multicenter Meningococcal Surveillance Study. White blood cell count (WBC), absolute neutrophil count, immature neutrophil count and immature-to-total neutrophil ratio were evaluated alone and in combination at diagnosis of invasive meningococcal disease.
Researchers found that 23.6% of the patients required mechanical ventilation, and 6.9% died. Taken individually, absolute neutrophil count ≤1,000/mm3 or ≥10,000/mm3 was found in 63.4% of participants, immature neutrophil count ≥500/mm3 in 78.7%, and immature-to-total neutrophil ratio ≥0.20 in 64.4%.
When taken in combination, however, they also found that one or more of the absolute neutrophil count, immature neutrophil count, or immature-to-total neutrophil ratio met these abnormal criteria in 94.4% of all cases. Notably, however, total WBC was normal in 33.3%.
“This is practical importance, since it indicated reliance on total WBC and total neutrophil count alone would have been falsely reassuring,” researchers wrote. “In addition, even slightly abnormal total WBC did not add any additional positive cases to those meeting with one of the other criteria.”
Disclosure: The study was funded in part by Sanofi-Pasteur.
Perspective
Back to Top
Morven S. Edwards, MD
One of the shared goals of pediatric caregivers is to identify, among the many children assessed with self-limited viral infections, the one child with early bacteremia that could progress to life-threatening infection if missed.
Demissie’s study of neutrophil of parameters thus draws in the reader with the hope that such assurance for recognition of invasive meningococcal infection can be found by assessing white blood cell parameters. The study found that 94% of 216 children with invasive meningococcal infection had abnormalities in the absolute neutrophil count, immature neutrophil count and/or immature-to-total nuetrophil ratio on the day of hospital admission.
The strategy of using a readily available, reasonably inexpensive test to identify invasive infection with Neisseria meningitidis is attractive as the proposed endotoxon-mediated pathogenesis for the neutrophil abnormalities. I would point out however, and the authors note as a limitation, the lack of a control group to determine the positive predictive value of criteria. Implementing the use of neutrophil parameters in clinical practice will require clarifying the extent of overlap of the abnormalities with those found in children with other febrile respiratory illnesses. Thus is true here, as is so often the case, that one set of findings raises questions prompting additional study because it is a laudable goal to optimize outcomes through accurate early diagnosis of invasive meningococcal infection.
Collapse
Click Here to Manage Email Alerts