From the Guidelines
Diagnosing a viral infection should be based on a combination of clinical evaluation and laboratory testing, with the use of PCR-based viral panels recommended to diagnose active viral infections and reactivations, as supported by the most recent evidence 1. When diagnosing a viral infection, a healthcare provider will first assess symptoms, which may include fever, fatigue, body aches, respiratory issues, or specific rashes depending on the virus.
- Laboratory tests are then used to confirm the diagnosis, including:
- Viral cultures, where samples are collected to grow the virus
- Polymerase chain reaction (PCR) tests, which detect viral genetic material
- Antigen tests that identify viral proteins
- Serological tests that measure antibodies produced in response to the infection
- Rapid diagnostic tests are available for many common viruses like influenza, COVID-19, and respiratory syncytial virus (RSV), and can provide results in a short amount of time, such as 30 minutes for some commercial rapid diagnostic tests 1.
- Sometimes, imaging studies such as chest X-rays may be needed to assess the impact of viral infections on organs. The diagnostic approach varies based on the suspected virus, with some requiring specialized testing at reference laboratories, and it is essential to consider the patient’s age, immune status, history, and many other variables when selecting the appropriate tests 1. The most effective diagnostic strategy is to use PCR-based viral panels, as recommended by the most recent evidence 1, to ensure accurate and timely diagnosis, which is crucial for appropriate treatment, infection control measures, and in some cases, initiating antiviral medications that work best when started promptly.
From the FDA Drug Label
Diagnosis RSV infection should be documented by a rapid diagnostic method such as demonstration of viral antigen in respiratory tract secretions by immunofluorescence3,4 or ELISA5 before or during the first 24 hours of treatment. To diagnose a viral infection, specifically RSV infection, rapid diagnostic methods should be used, such as:
- Demonstration of viral antigen in respiratory tract secretions by immunofluorescence
- ELISA These methods should be performed before or during the first 24 hours of treatment 2.
From the Research
Diagnosis of Viral Infections
Diagnosing viral infections can be challenging, but various methods are available to aid in the process. Some of these methods include:
- Rapid influenza antigen diagnostic test (RIDT) for influenza virus infection, although it may produce false-negative results 3
- Nucleic acid amplification test, such as quantitative reverse transcription-polymerase chain reaction (qRT-PCR), which offers high sensitivity and can detect small quantities of the virus 3
- Molecular diagnostics, which have led to increased recognition of viral pathogens 4
- Laboratory techniques, such as biochemical assays, microscopy, and nucleic acid amplification, for detecting the presence of the virus or antibodies in the blood 5
- Point-of-care (POC) techniques, including microfluidics-based tests, for on-spot testing 5
- Infrared microscopy of peripheral human blood samples and multivariate analysis, which can rapidly identify the etiology of infection 6
- Virus detection and serological conversion, as well as point-of-care combination tests, for diagnosing dengue virus infection 7
Laboratory and Point-of-Care Techniques
Laboratory and point-of-care techniques play a crucial role in the diagnosis of viral infections. These techniques include:
- Quantitative RT-PCR for evaluating influenza virus infection 3
- Nucleic acid amplification for detecting herpes simplex virus (HSV) 5
- Biochemical assays and microscopy for detecting the presence of the virus or antibodies in the blood 5
- Microfluidics-based tests for on-spot testing 5
- Infrared spectroscopic method for rapid identification of bacterial and viral infections 6
- Point-of-care combination tests for detecting markers of infection present during different stages of infection 7
Challenges and Limitations
Despite the availability of various diagnostic methods, there are still challenges and limitations in diagnosing viral infections, including:
- False-negative results from RIDT 3
- Cross-reactivity of antibody responses among flaviviruses, making differential diagnosis challenging 7
- Lack of a single, definitive diagnostic biomarker for dengue virus infection 7
- Need for rapid and reliable identification of the etiology of infection to guide effective treatment 6