The FebriDX point-of-care immunoassay can quickly determine whether an infection is bacterial or viral

The FebriDX point-of-care immunoassay can quickly determine whether an infection is bacterial or viral

In a current one JAMA network opened In this study, researchers are investigating whether a point-of-care immunoassay called FebriDx can differentiate between bacteria- and virus-induced immune responses in acute respiratory infections using levels of myxovirus resistance protein A (MxA) and C-reactive protein (CRP). Collect blood samples.

Study: Diagnostic accuracy of a point-of-care test for bacterial and viral biomarkers in the outpatient setting.Photo credit: Illustration Forest / Shutterstock.com

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Most outpatient visits in the United States are related to acute respiratory infections such as pneumonia, sinusitis, pharyngitis, and bronchitis. These respiratory infections may be bacterial or viral in nature or may be non-infectious, and identification of the etiologic agent is often difficult. Diagnostic uncertainty leads doctors to overprescribe antibiotics to rule out possible bacterial infections and prevent sepsis, thereby contributing to antibiotic resistance.

An accurate diagnostic test could help prescribe the right medications and avoid antibiotic misuse. The FebriDx bacterial and viral diagnostic test is a 10-minute point-of-care immunoassay that can measure MxA and CRP levels from fingerstick blood samples and differentiate between viral and bacterial respiratory infections.

CRP levels are nonspecific indicators of inflammation and infection, while MxA levels are modulated by type 1 interferons, which are secreted in response to viral infections. Therefore, elevated CRP levels without an increase in MxA levels would indicate a bacterial infection.

While the principles on which the FebriDx test is based are logical, the test's ability to distinguish between bacterial and viral respiratory infections needs to be verified.

About the study

The prospective, blinded, observational study included participants ages 1 to 21 years, 22 to 64 years, and 65 years or older who presented to outpatient clinics with fever and clinical symptoms of acute respiratory infections such as nasal congestion, cough, sore throat, and rhinorrhea.

A corresponding control group with no signs or symptoms of infection was also included. Individuals who received antiviral drugs, antibiotics, live immunization, interferon therapy, immunosuppression, major surgery, or myocardial infarction were excluded from the study.

Fingerstick blood samples were taken from all study participants. In addition, comparative tests were carried out to clearly classify the disease as a bacterial or viral infection.

Comparative testing included multiplex polymerase chain reaction (PCR) testing of oro- and nasopharyngeal swabs for a range of respiratory infections and real-time quantitative PCR (RT-qPCR) for various viruses, including herpes simplex viruses, Epstein-Barr virus, gonorrhea virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

PCR testing was also performed for Fusobacterium necrophorum and human bocavirus. In addition, complete blood count and serum levels of calcitonin and anti-Epstein-Barr immunoglobulin M (IgM) antibodies were also measured.

Participants were followed up after seven days to confirm the diagnosis. The performance of the test based on demographic factors of gender, race, and ethnicity was also analyzed. Based on the comparison algorithm, diagnostic accuracy was calculated by comparing FebriDx results with the final diagnosis.

Study results

FebriDx was reported to have a sensitivity of 93.2% and a negative predictive value of 98.7% for detecting and preventing bacterial infections. Compared to the results of the comparison algorithm, the test was associated with a specificity of 88% and a positive predictive value of 89.7% for detecting viral respiratory infections.

FebriDx confirmed bacterial infections with a negative predictive value and a sensitivity of 100%, indicating its potential to guide antibiotic treatment. The low positive predictive value of 58.1% for bacterial infections could be due to excessive antibiotic prescriptions. However, use of the diagnostic test showed a 2.4:1 decrease in antibiotic prescriptions based on accurate clinical diagnoses.

Because CRP is not specific for bacterial infections and increases in infections with viruses such as influenza and SARS-CoV-2, it is not a reliable indicator of bacterial infections. On the other hand, the increase in MxA proteins in viral infections makes the comparative values ​​of CRP and MxA a more reliable indicator for detecting bacterial and viral infections.

Simultaneous detection of MxA and CRP levels was found to diagnose bacterial and viral respiratory infections with a specificity range of 76–94% and 80–95%, respectively.

Conclusions

The current study evaluated the accuracy and sensitivity of the FebriDx point-of-care immunoassay in distinguishing between bacterial and viral respiratory tract infections using fingerstick blood samples.

To this end, this immunoassay met the specified criteria for the successful detection of host immune responses caused by bacteria or viruses. In addition, FebriDx could finally rule out bacterial infections and thus make unnecessary antibiotic prescriptions unnecessary.

Increasing the rate of accurate diagnoses through the use of FebriDx may help reduce side effects and the development of antibiotic resistance in bacteria.

Reference:

• Shapiro, NI, Filbin, MR, Hou, et al. (2022). Diagnostische Genauigkeit eines Point-of-Care-Tests auf bakterielle und virale Biomarker im ambulanten Bereich. JAMA Network Open 5(10), e2234588. doi:10.1001/jamanetworkopen.2022.34588.