What laboratory test is used to differentiate between viral and bacterial infections?

From the Guidelines

The most effective lab test to determine viral versus bacterial illness is the Multiplex molecular assays, which can detect multiple respiratory pathogens, including influenza A or B viral RNA, and other viral or bacterial targets, with high sensitivity and specificity. This is based on the evidence from the study published in Pediatrics in 2021 1, which compared different types of influenza diagnostic tests, including rapid molecular assays, rapid influenza diagnostic tests, and molecular assays. The study found that multiplex molecular assays have high sensitivity and specificity, and can provide rapid results, making them a preferred choice for diagnosing respiratory viruses.

Some of the key benefits of multiplex molecular assays include:

• High sensitivity and specificity
• Ability to detect multiple respiratory pathogens
• Rapid turnaround time
• High-performance characteristics

Other lab tests, such as C-reactive protein (CRP) test, procalcitonin (PCT) test, and complete blood count (CBC) with differential, can also be used to help determine whether an illness is viral or bacterial in nature, but they are not as accurate as multiplex molecular assays 1. Rapid antigen tests and PCR tests for specific pathogens may also be used when particular infections are suspected, but they may not be as sensitive or specific as multiplex molecular assays.

It's worth noting that the choice of lab test may depend on the specific clinical scenario, and the availability of testing resources. However, based on the evidence, multiplex molecular assays are the most effective lab test for determining viral versus bacterial illness, and should be considered as the first-line diagnostic test for patients with suspected respiratory infections.

From the Research

Laboratory Tests for Viral versus Bacterial Illness

• The distinction between viral and bacterial infections is crucial for proper treatment and to reduce unnecessary antibiotic use 2.
• Various laboratory tests can be used to determine the cause of an illness, including:
  • Rapid antigen detection tests, such as the SOFIA Influenza A+B test 3.
  • Nucleic acid amplification tests (NAAT), such as the Luminex x-TAG respiratory viral panel assay 3.
  • Chemiluminescent signatures of circulating phagocytes 4.
  • RT-PCR assays, such as the STANDARD M10 Flu/RSV/SARS-CoV-2 assay 5.
• These tests can help guide patient management, antiviral therapy, infection prevention strategies, and epidemiologic monitoring 6.

Specific Laboratory Tests

• The SOFIA Influenza A+B test is a rapid antigen detection test that can provide a rapid diagnosis of influenza A and B viruses 3.
• The Luminex x-TAG respiratory viral panel assay is a NAAT that can detect multiple respiratory viruses, including influenza A and B viruses, and respiratory syncytial virus (RSV) 3.
• The STANDARD M10 Flu/RSV/SARS-CoV-2 assay is a RT-PCR assay that can detect influenza A, influenza B, RSV, and SARS-CoV-2 in one hour or less 5.

Limitations and Considerations

• The sensitivity and specificity of rapid antigen detection tests can vary, and confirmatory molecular testing may be recommended for negative test results 3.
• The choice of laboratory test depends on various factors, including the clinical presentation, epidemiologic context, and availability of testing 6, 2.