Considerations for SARS-CoV-2 testing: Outpatient bronchiolitis
If a child presents with classic bronchiolitis but has above moderate to severe symptoms, is SARS-CoV-2 a consideration? Perhaps, if SARS-CoV-2 acts similarly to non-SARS-CoV-2s.
A recent report from the 30th Multicenter Airway Research Collaboration (MARC-30) surveillance study (2007-2014) of children hospitalized with clinical bronchiolitis evaluated respiratory viruses, including RSV and the four common non-SARS coronaviruses using molecular testing.3 Among 1,880 subjects, a CoV (alpha CoV: NL63 or 229E, or beta CoV: KKU1 or OC43) was detected in 12%. Yet most had only RSV (n = 1,661); 32 had only CoV (n = 32). But note that 219 had both.
Bronchiolitis subjects with CoV were older – median 3.7 (1.4-5.8) vs. 2.8 (1.9-7.2) years – and more likely male than were RSV subjects (68% vs. 58%). OC43 was most frequent followed by equal numbers of HKU1 and NL63, while 229E was the least frequent. Medical utilization and severity did not differ among the CoVs, or between RSV+CoV vs. RSV alone, unless one considered CoV viral load as a variable. ICU use increased when the polymerase chain reaction cycle threshold result indicated a high CoV viral load.
These data suggest CoVs are not infrequent coinfectors with RSV in bronchiolitis – and that SARS-CoV-2 is the same. Therefore, a bronchiolitis presentation doesn’t necessarily take us off the hook for the need to consider SARS-CoV-2 testing, particularly in the somewhat older bronchiolitis patient with more than mild symptoms.
Considerations for SARS-CoV-2 testing: Outpatient influenza-like illness
In 2020-2021, the Centers for Disease Control and Prevention recommends considering empiric antiviral treatment for ILIs (fever plus either cough or sore throat) based upon our clinical judgement, even in non-high-risk children.4
While pediatric COVID-19 illnesses are predominantly asymptomatic or mild, a febrile ARI is also a SARS-CoV-2 compatible presentation. So, if all we use is our clinical judgment, how do we know if the febrile ARI is due to influenza or SARS-CoV-2 or both? At least one study used a highly sensitive and specific molecular influenza test to show that the accuracy of clinically diagnosing influenza in children is not much better than flipping a coin and would lead to potential antiviral overuse.5
So, it seems ideal to test for influenza when possible. Point-of-care (POC) tests are frequently used for outpatients. Eight POC Clinical Laboratory Improvement Amendments (CLIA)–waived kits, some also detecting RSV, are available but most have modest sensitivity (60%-80%) compared with lab-based molecular tests.6 That said, if supplies and kits for one of the POC tests are available to us during these SARS-CoV-2 stressed times (back orders seem more common this year), a positive influenza test in the first 48 hours of symptoms confirms the option to prescribe an antiviral. Yet how will we have confidence that the febrile ARI is not also partly due to SARS-CoV-2? Currently febrile ARIs usually are considered SARS-CoV-2 and the children are sent for SARS-CoV-2 testing. During influenza season, it seems we will need to continue to send febrile outpatients for SARS-CoV-2 testing, even if POC influenza positive, via whatever mechanisms are available as time goes on.
We expect more rapid pediatric testing modalities for SARS-CoV-2 (maybe even saliva tests) to become available over the next months. Indeed, rapid antigen tests and rapid molecular tests are being evaluated in adults and seem destined for CLIA waivers as POC tests, and even home testing kits. Pediatric approvals hopefully also will occur. So, the pathways for SARS-CoV-2 testing available now will likely change over this winter. But be aware that supplies/kits will be prioritized to locations within high need areas and bulk purchase contracts. So POC kits may remain scarce for practices, meaning a reference laboratory still could be the way to go for SARS-CoV-2 for at least the rest of 2020. Reference labs are becoming creative as well; one combined detection of influenza A, influenza B, RSV, and SARS-CoV-2 into one test, and hopes to get approval for swab collection that can be done by families at home and mailed in.
Summary
Expect variations on the traditional parade of seasonal respiratory viruses, with increased numbers of coinfections. Choosing the outpatient who needs influenza testing is the same as in past years, although we have CDC permissive recommendations to prescribe antivirals for any outpatient ILI within the first 48 hours of symptoms. Still, POC testing for influenza remains potentially valuable in the ILI patient. The choice of whether and how to test for SARS-CoV-2 given its potential to be a primary or coinfecting agent in presentations linked more closely to a traditional virus (e.g. RSV bronchiolitis) will be a test of our clinical judgement until more data and easier testing are available. Further complicating coinfection recognition is the fact that many sick visits occur by telehealth and much testing is done at drive-through SARS-CoV-2 testing facilities with no clinician exam. Unless we are liberal in SARS-CoV-2 testing, detecting SARS-CoV-2 coinfections is easier said than done given its usually mild presentation being overshadowed by any coinfecting virus.
But understanding who has SARS-CoV-2, even as a coinfection, still is essential in controlling the pandemic. We will need to be vigilant for evolving approaches to SARS-CoV-2 testing in the context of symptomatic ARI presentations, knowing this will likely remain a moving target for the foreseeable future.
Dr. Harrison is professor of pediatrics and pediatric infectious diseases at Children’s Mercy Hospital-Kansas City, Mo. Children’s Mercy Hospital receives grant funding to study two candidate RSV vaccines. The hospital also receives CDC funding under the New Vaccine Surveillance Network for multicenter surveillance of acute respiratory infections, including influenza, RSV, and parainfluenza virus. Email Dr. Harrison at [email protected].
References
1. Pediatrics. 2020;146(1):e20200961.
2. JAMA. 2020 May 26;323(20):2085-6.
3. Pediatrics. 2020. doi: 10.1542/peds.2020-1267.
4. www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm.
5. J. Pediatr. 2020. doi: 10.1016/j.jpeds.2020.08.007.
6. www.cdc.gov/flu/professionals/diagnosis/table-nucleic-acid-detection.html.
