Another Perspective: Should We Swab for Group A Streptococcus?

We are gratified to see the new American Academy of Pediatrics clinical report regarding pediatric acute-onset neuropsychiatric syndrome (PANS).1 Acknowledging that this is likely a “valid diagnosis” is an important first step toward alleviating the suffering of children and families and offering guidance for pediatric health care providers. Although the pathogenesis and etiology are not fully clarified, pediatric autoimmune neuropsychiatric disorder associated with Streptococcus (PANDAS), a PANS subset, is by its name and diagnostic criteria clearly associated with group A streptococcus (GAS).The clinical report emphasizes the unique and distinctive neurobehavioral symptoms in children with PANS and PANDAS to be the dramatic acuity of onset and short time to peak severity of the cardinal symptoms of obsessive-compulsive disorder (OCD), tics, or food restriction. Although the incidence of PANS/PANDAS is not definitively established, restriction of the diagnosis to those who fit this stringent characteristic suggests that it is uncommon.2An important question is whether microbiologic testing to determine the presence of GAS is appropriate when a child presents with acute neurobehavioral signs and symptoms suggestive of PANS without clinical evidence of pharyngitis. The dilemma is created because GAS is a common cause of both clinical and subclinical pharyngitis and is often “carried” in the pharynx as normal flora. Accordingly, there is concern that searching for GAS may yield positive results, which are not actually causative, risking antibiotic overuse. However, this leap is taken whenever we swab a child for GAS, whether symptomatic or asymptomatic: if we identify GAS, we are committed to consider it causative and treat appropriately. It is critical to understand, that in the well-recognized postinfectious nonsuppurative complication of GAS, acute rheumatic fever, two-thirds of patients do not have memorable clinical pharyngitis, indicating the importance of subclinical infection.3,4Contemporary studies corroborate the very high frequency of GAS subclinical infection in school-aged children.5,6 Our current “best formulation” of PANS/PANDAS pathogenesis is that these conditions are triggered by an autoimmune reaction to GAS, as in acute rheumatic fever. Thus, performing a microbiologic test to seek GAS seems appropriate. To avoid antibiotic overuse, our case definition should be stringent. Evaluating children suspected to have PANS for GAS should be undertaken only if the cardinal symptom, generally OCD, had a hyperacute (explosive) onset (usually <48 hours and never >72 hours to peak severity) with dramatic behavioral manifestations.It is traditional to obtain antistreptolysin-O and anti-DNase B serologies as diagnostic/supportive criteria for GAS infections. However, data show that at least one-third of new GAS infections are not accompanied by changes in these antibody levels and that some children have sustained high or low levels following new acquisitions.6 A single serologic assessment is not valuable. If sequential samples are separated by at least 21 days, a significant change in antibody level may support recent infection. An absence of change or a negative study result does not rule out infection, as the immunologic response to a new infection may be limited to antistreptococcal antibodies that are not available commercially. If despite the limitations of serology there is still interest, the provider should be urged to obtain sequential samples to facilitate interpretation.