ID Consult

WBC Count Prevents Unnecessary Antibiotics for Enterovirus


It’s summertime, which means that pediatric and family medicine offices are filled with children who have enteroviral infections, and too many of them will receive inappropriate antibiotic prescriptions.

From June through September, children who present with fever and other flulike symptoms nearly always have a nonpolio enterovirus (NPEV) infection, with coxsackievirus groups A and B, echoviruses, and the newer numbered enteroviruses being the most common in the United States. Epidemiologic surveillance suggests that 10 million to 15 million illnesses attributable to NPEV occur in the United States each year. I tell parents that their child has a "summer flu," which helps to communicate that it is usually self-limited and that antibiotics will not work to treat it.

Dr. Michael E. Pichichero

A sudden high fever is usually what brings the child in, and the classic blistering hand-foot-mouth presentation of enterovirus helps us nail down the diagnosis. But sometimes, especially in younger children, symptoms such as myalgia, malaise, irritability, upper respiratory symptoms, or gastrointestinal symptoms may be nonspecific. In addition, the fever can precede hand-foot-mouth blisters by several days. A 9-month-old with a sudden fever of 103° F and a mildly red-looking throat can cause panic for parents, and a physician will often be led to prescribe an antibiotic out of an abundance of caution. In fact, more than 80% of inappropriate antibiotic use in the summertime is for febrile illness related to early enteroviral infection combined with worried parents and physicians.

Obtaining a complete blood count and differential can solve this problem, but it’s often not done because typically it involves sending the patient out for the blood work and waiting 4-6 hours for the results. Depending on when the test is done, results may not be available until the following day. It’s much simpler to "cover" with an antibiotic than to order the diagnostic test.

But I believe we should be using the white blood cell (WBC) count rather than prescribing antibiotics. The WBC count will almost always be low, and if a differential is added it will show a predominance of lymphocytes, indicating a viral infection. With that, parents and physicians can be reassured it’s enterovirus, and that no antibiotic is required.

In recent years, large pediatric practices and urgent care centers have begun purchasing a point-of-care WBC test made by Hemacue. Currently, it is licensed for use only in level 3 Clinical Laboratory Improvement Amendments (CLIA) facilities. A couple of years ago, I testified before a Food and Drug Administration device panel urging broader availability for the machine in clinical practice, but the panel had concerns that physicians would overrely on the WBC – the machine doesn’t give the differential – and possibly miss a more significant illness, such as leukemia.

Of course, the current widespread practice of empirically prescribing an antibiotic with no lab testing won’t pick up leukemia, either. In my view, the point-of-care test is an aid. It’s a piece of information you add to your clinical history and physical exam that assists in your diagnosis. I believe the benefits of avoiding unnecessary antibiotic use in millions of children every summer far outweigh the theoretical possibility that pediatricians would not rely on the broader context, including the time of year, disease rates in the community, and their clinical judgment. I really believe that WBC testing constitutes better care.

My colleagues and I have published two papers regarding the use of the WBC test to aid in judicious antibiotic use. In one, a prospective, 3-year study of 1,956 patients aged 3 months to 21 years with acute upper respiratory illness and fever, 737 did not have a diagnosis established by history and physical. Of those patients, we had WBC counts done for 351 children who appeared ill, had a temperature greater than 101° F, and parents who were demanding an antibiotic or physicians who were inclined to give an antibiotic. Of those, just 14 had a WBC count of 15,000/mcL or greater, and an antibiotic was prescribed for 13 of them. With the selective use of WBC testing, no child had significant bacterial illness that was missed (Clin. Pediatr. [Phila] 2003;42:113-9).

In another study of 120 acutely ill children and potential antibiotic recipients, we found that the point-of-care Hemacue WBC device produced comparable results to the Cell-Dyn countertop machine for total WBC counts (Clin. Pediatr. [Phila] 2009;48:291-4).

I’d just like to add a few more points about enterovirus to keep in mind when you advise patients and families. There is a long-held notion that summer viruses enteroviruses in particular – are of shorter duration than are winter viruses such as influenza, parainfluenza, and respiratory syncytial virus. That’s actually not true. Several years ago, my colleagues and I prospectively studied 380 children aged 4-18 years with systemic NPEV syndromes who presented to private suburban pediatric practices. Overall, NPEV infections were virologically confirmed in 122 of 372 patients (33%). The median duration of illness was 6 days for those with rash, 7 days for those with hand-foot-mouth and viral meningitis, 8 days for those with pleurodynia, and 9 days for those with myalgia/malaise (Pediatrics 1998;102:1126-34). Many children were ill for 10 days to 2 weeks.


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