Respiratory season preparation often focuses on capacity: ensuring instruments are ready, supplies are available, and staffing plans can accommodate higher testing volumes. Those are important considerations. But laboratory leaders also have an opportunity to ask a different question before respiratory case volumes rise: Will our testing pathway provide the information clinicians need to make treatment decisions when patient volumes surge?

Influenza, respiratory syncytial virus (RSV), COVID-19, and other respiratory infections predictably increase demand across emergency departments, inpatient units, and laboratories each year. As volumes rise, clinicians must make time-sensitive decisions about antibiotic therapy, additional diagnostic evaluation, observation, admission, or discharge, often before the full clinical picture is available.

Many health systems have expanded access to rapid molecular respiratory testing, improving the ability to identify viral pathogens. Yet even after a viral pathogen is detected, an important question may remain unanswered: does the patient also have a bacterial infection that requires a different management approach? Before respiratory season begins, laboratory leaders can work with emergency medicine, infectious disease, antimicrobial stewardship, and pharmacy teams to identify where these diagnostic gaps occur and determine whether additional testing approaches could help address them.

Identifying diagnostic gaps after pathogen testing

Molecular respiratory testing has transformed the identification of viral pathogens, allowing influenza, SARS-CoV-2, RSV, and other respiratory viruses to be detected rapidly and with high analytical sensitivity. These assays provide important pathogen-specific information, but they do not establish whether a bacterial infection is also present. As a result, clinicians may still face uncertainty regarding antibiotic treatment decisions even after a viral pathogen has been identified.

For laboratory leaders reviewing respiratory-season testing pathways, an important question is whether existing testing sufficiently addresses this bacterial-versus-viral uncertainty or whether additional diagnostic information may be needed. For example, MeMed BV is an FDA-cleared host-immune response test intended to help clinicians differentiate bacterial from viral infections. The test integrates measurements of three host proteins—tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), interferon gamma-induced protein 10 (IP-10), and C-reactive protein (CRP) — into a bacterial-versus-viral likelihood score.^¹

Unlike respiratory panels that detect specific pathogens, MeMed BV evaluates a patient’s immune response to infection. The test’s diagnostic performance was evaluated in a prospective, multicenter study (NCT04690569), that enrolled 476 adults and children presenting to emergency departments and urgent care centers with suspected acute infection with respiratory tract infection identified as the predominant clinical syndrome. MeMed BV demonstrated 90.0% sensitivity and 92.8% specificity for bacterial infection, with a negative predictive value of 98.8%. Approximately 7% of test results fell into the equivocal range.^¹ The test is intended to complement, not replace, pathogen-directed testing and other elements of the diagnostic evaluation. Results should be interpreted in the context of the patient's overall clinical presentation and other available findings.^¹˒²

This distinction between pathogen detection and host-response assessment is particularly relevant during respiratory season, when laboratories must decide whether the test menu provides the information clinicians need to make timely treatment decisions. Several studies have evaluated how host-response testing influences antibiotic prescribing in different clinical settings. 

Supporting antibiotic decisions in acute care

Clinicians treating acutely ill patients must often decide whether to prescribe antibiotics before the full diagnostic picture is available. If bacterial infection is uncertain, prescribing may seem like the safer choice. While bacterial infections require prompt recognition and treatment, unnecessary antibiotic use can harm patients and contribute to antimicrobial resistance.

Studies have examined how host-response results affect antibiotic prescribing across a range of clinical settings. When interpreting these data, it is important to consider the patient population being studied, as the clinical questions and decisions may differ between outpatient, urgent care, and higher-acuity emergency department settings.

Evidence in patients likely to be managed as outpatients

The JUNO pilot study, a randomized controlled trial, evaluated the effect of MeMed BV on antibiotic prescribing in emergency department and urgent care patients with suspected lower respiratory tract infection who were ultimately discharged home.^³ Among patients with a viral MeMed BV result, antibiotic prescribing decreased from 25% with standard care to 12% with MeMed BV, without an increase in seven-day return visits.^³ These findings suggest that host-response testing may help support antibiotic decision-making in selected patients being considered for outpatient management.

A 2025 pragmatic cohort study evaluated MeMed BV across 10 urgent care centers, including 3,920 adults treated by 144 physicians. Viral MeMed BV results were associated with avoiding potentially unwarranted antibiotic prescriptions in 63.1% of cases in which physicians had initially intended to prescribe antibiotics. Conversely, bacterial results prompted antibiotic treatment in 69.9% of cases in which physicians had not initially planned to prescribe them.^⁴

Evidence in higher-acuity emergency department populations

A 2025 real-world study by LoVerde and colleagues evaluated MeMed BV in adult emergency department patients for whom blood cultures had been ordered.^² This population represents patients in whom clinicians had sufficient concern about infection severity or diagnostic uncertainty to pursue additional evaluation. Patients with viral MeMed BV results had a significant decrease in antibiotic use, from 80.7% during the first study period to 61.4% during the second. Hospital admissions also declined, from 77.3% to 61.4%, although this difference did not reach statistical significance.^²

Across these studies, MeMed BV influenced antibiotic use in both directions, helping clinicians withhold antibiotics when bacterial infection appeared less likely and initiate treatment when it appeared more likely. Together, the findings suggest that host-response testing may provide information that complements pathogen-directed testing, although the potential impact depends on the clinical setting and patient population in which it is used.

Turnaround time is another consideration. For a host-response result to inform treatment or disposition decisions, it must be available while those decisions are being made. MeMed BV generates results in about 15 minutes on the MeMed Key platform, allowing clinicians to consider the result alongside other clinical findings during the acute-care visit.^¹

Preparing the lab for respiratory season

Respiratory season preparation should start with a review of the previous season. Which assays experienced the largest volume increases? Where did turnaround times lengthen? Were clinicians ordering multiple tests to answer overlapping questions? Did diagnostic gaps persist even after respiratory panel results were available?

That review can guide discussions across laboratory, clinical, stewardship, pharmacy, and operations. Before the seasonal surge, teams can determine where each assay fits in the care pathway, which patients should be tested, who will order it, and how results will be reported and used.

Clinicians also benefit from understanding how a new test differs from existing assays. With host-response testing, teams need to recognize that the result reflects the patient’s immune response and is intended to aid bacterial-versus-viral differentiation. It should be interpreted within the patient’s overall clinical picture rather than as a standalone answer.^¹

Operational planning includes anticipating testing volume, reagent and supply needs, staffing, quality control, result reporting, and communication with clinical teams. Addressing these considerations in advance can help prepare for increased testing demands during respiratory season.^⁵ 

Diagnostic stewardship should also be part of that planning. Large respiratory panels can be valuable in appropriate patients, but broader pathogen testing does not answer every clinical question. If the unresolved question is whether a bacterial infection is present, additional pathogen testing may not provide that clarity.

When considering host-response testing such as MeMed BV, labs can identify where bacterial-versus-viral differentiation could help guide antibiotic treatment, further evaluation, and admission or discharge.

Close diagnostic gaps before they affect care

Before respiratory volumes rise, laboratory leaders should review where the current testing pathway stops short of answering the treatment question. In partnership with emergency, urgent care, infectious disease, and antimicrobial stewardship teams, labs can define the appropriate patient population, determine where host-response testing may add value, and establish how results will be used and measured.

References

1. Bachur RG, Kaplan SL, Arias CA, et al. A rapid host-protein test for differentiating bacterial from viral infection: Apollo diagnostic accuracy study. J Am Coll Emerg Physicians Open. 2024;5(3). doi:10.1002/emp2.13167.
2. LoVerde A, Ghitan M, Bodenstein H, et al. Real-world study assessing sensitivity and clinical utility of a host-protein test in adult emergency department patients with blood culture ordered. J Am Coll Emerg Physicians Open. 2025;6(6):100255. doi:10.1016/j.acepjo.2025.100255.
3. Singer AJ, Hollander JE, Kean ER, et al. Effect of host-protein test (TRAIL/IP-10/CRP) on antibiotic prescription and emergency department or urgent care center return visits: The JUNO pilot randomized controlled trial. Acad Emerg Med. 2025;32:975-984. doi:10.1111/acem.70031.
4. Kalmovich B, Rahamim-Cohen D, Yehoshua I, Kivity S, Orvieto N, Shapiro Ben David S. Implementation of a rapid host-protein diagnostic test for distinguishing bacterial and viral infections in adults presenting to urgent care centers: a pragmatic cohort study. BMC Med. 2025;23:63. doi:10.1186/s12916-025-03903-8.
5. Association of Public Health Laboratories. Laboratory-Epidemiology Respiratory Virus Surveillance Seasonal Planning and Coordination Checklist. APHL. Accessed September 10, 2026. https://aphl.org/docs/default-source/technical/id-lab-epi-respiratory-planning-checklist.pdf.