From the Guidelines
Over-the-counter tests for flu can detect the H3N2 strain, but their ability to do so may vary depending on the specific test used, as some tests are more sensitive than others in detecting influenza A viruses, including H3N2. According to a study published in 2012 1, an evaluation of seven FDA-cleared rapid influenza diagnostic tests (RIDTs) found that only four of them (Directigen, Sofia, Veritor, and Xpect) detected all influenza A (H3N2)v viruses. The other tests, such as BinaxNOW, QuickVue, and FluAlert, had lower detection rates, ranging from 1 to 5 out of 7 H3N2v viruses. This suggests that while some over-the-counter flu tests may be able to detect H3N2, their sensitivity and accuracy can vary. It's also important to note that these tests typically detect viral proteins called antigens that are present in all influenza A viruses, including the H3N2 subtype, but they may not specifically distinguish between different influenza A subtypes like H1N1 or H3N2, as stated in a previous report from 2008 1. COVID-19 tests, on the other hand, are specifically designed to detect SARS-CoV-2 and will not detect influenza viruses like H3N2. For a definitive subtype identification, laboratory-based PCR testing ordered by a healthcare provider would be necessary. Key points to consider include:
- The sensitivity of over-the-counter flu tests in detecting H3N2 can vary depending on the specific test used
- Some tests, such as Directigen, Sofia, Veritor, and Xpect, have been shown to detect all influenza A (H3N2)v viruses, while others have lower detection rates
- These tests typically detect viral proteins called antigens that are present in all influenza A viruses, but may not specifically distinguish between different influenza A subtypes
- COVID-19 tests will not detect influenza viruses like H3N2
- Laboratory-based PCR testing is necessary for definitive subtype identification.
From the Research
Over-the-Counter Tests for Flu and Covid
- The provided studies do not directly address the ability of over-the-counter tests for flu and Covid to detect H3N2.
- However, the studies discuss the diagnosis and treatment of influenza, including the use of rapid molecular assays and neuraminidase inhibitors such as oseltamivir and zanamivir 2, 3, 4, 5, 6.
- Influenza A(H3N2) is a subtype of influenza A that can cause significant morbidity and mortality, and its detection is crucial for effective treatment 3, 4.
- The studies suggest that rapid molecular assays are highly accurate and can be used at the point of care to diagnose influenza, but they do not specifically mention over-the-counter tests 2.
- Neuraminidase inhibitors such as oseltamivir and zanamivir are effective in treating influenza A(H3N2) infection, but their use is typically prescribed by a healthcare professional and not available over-the-counter 3, 4, 5, 6.
Detection of H3N2
- The studies do not provide information on the ability of over-the-counter tests to detect H3N2 specifically.
- However, they discuss the importance of monitoring susceptibility of influenza viruses to neuraminidase inhibitors and the use of assays such as the neuraminidase inhibition (NI) assay and genotypic assays to detect molecular markers associated with resistance 5.
- The development of rapid, high-throughput assays such as real-time RT-PCR and pyrosequencing has improved the detection of influenza viruses, including H3N2, but these assays are typically used in clinical and laboratory settings rather than over-the-counter tests 5.