Technical details: FebriDx

FebriDx identifies clinically significant infections that have an associated systemic immune response and can achieve a 97% negative predictive value for bacterial infection, making FebriDx an ideal triage test to help drive antibiotic stewardship in the outpatient setting.

FebriDx is the first and only rapid, in-office test that uses a fingerstick blood sample to help identify patients suffering from a clinically significant acute respiratory infection as well as differentiate viral from bacterial etiology of disease.

The FebriDx test is a single use disposable test that requires no ancillary equipment and simultaneously detects elevated levels of two biomarkers: Myxovirus resistance A (MxA) – an intracellular protein that becomes elevated in the presence of acute viral infection, and C-reactive protein (CRP) – an acute-phase protein that is elevated in the presence of bacterial infection. CRP is known to identify clinically significant infections, as recommended by the NICE Guidelines, but is very nonspecific, making it unable to effectively differentiate a viral from a bacterial infection. However, MxA provides the specificity required to best interpret the CRP results. The confirmation of elevated levels of MxA with or without the presence of elevated CRP identifies a viral infection while the elevation of CRP without an associated elevation in MxA confirms a bacterial infection. The lack of elevation of either MxA or CRP suggests that it is not a clinically significant infection. Additionally, antigen and molecular testing cannot differentiate the colonization, or the carrier state, which has been established for both viruses and bacteria; the tests ultimately lead to antibiotic overtreatment.

Serum-based biomarkers utilizing CRP and procalcitonin have been shown to effectively guide clinical management and therapeutic decisions without impacting morbidity and mortality. However, without the simultaneous use of MxA to provide the specificity, antibiotics are still frequently overprescribed.

Find out more:

European Clinical Respiratory Journal: Evaluation of a combined MxA and CRP point-of-care immunoassay to identify viral and/or bacterial immune response in patients with acute febrile respiratory infection (Sambursky and Shapiro)

1. FebriDx package insert: SPEC-MKT-044.