Care About Point of Care Tests for the Diagnosis of Respiratory Virus Infections - is There a Third Way?

There has been an increased focus on rapid diagnostic tests for respiratory virus infections and more effective infection control and antimicrobial management. Many studies1-3 have reported favourable performance results of point of care tests (POCT) including lateral flow device (LFD) antigen detection or isothermal nucleic acid detection tests run in Emergency Departments (ED).

The advantages of POCT include near patient testing, not sending samples to a laboratory, ease of the test process and result availability within 15 minutes. In contrast, many polymerase chain reaction (PCR) based assays involve sending samples outside the ED, are more labour intensive and a result can take from 1-4 hours.

The PCR assays can detect viral nucleic acid (NA), using real-time reverse transcription that can be a modular, cartridge-based or a larger random access design. Although LFD test sensitivity is around 70% with a much higher specificity, compared with PCR test sensitivity of >95% and high specificity too, this may be considered to be a reasonable trade off when taking assay cost and labour into consideration. Rapid molecular POCT, particularly those based on isothermal amplification technologies, could bridge the gap between traditional PCR and antigen tests. These assays are more sensitive than LFD tests, a result is available within 13 minutes and does involve an instrument with a small footprint that can be ward-based.

In an ED setting, these are key attributes, although the need for rapid results in 15 minutes is debatable when many patients are in EDs for longer time periods before being admitted. That could mean a PCR based assay with a higher test sensitivity could be carried out. An added issue is the move to centralise laboratories off-site, but cartridge-based PCR assays could be run in an on-site essential services laboratory with the time to result of around 1 hour.

Another consideration is the focus on influenza A and B virus, SARS-CoV-2 and RSV infections using POCT and not on the rest of the viral targets including adenovirus, parainfluenza virus, rhinovirus and enterovirus infections. This may be due to the lack of many antiviral treatment options for the latter group, but those viruses are also important from an infection control perspective. Moreover, viral variation needs to be considered, especially with SARS-CoV-2 and influenza virus variants that could affect detection.

In addition to these considerations, the sensitivity and range of viral targets of a POCT can also significantly impact antimicrobial stewardship; antibiotics may be started based on a negative result. Meta-analyses have demonstrated that rapid multiplex respiratory virus molecular testing can improve appropriate antiviral use, reduce unnecessary antibiotic administration and improve infection control management.4,5

LFD test sensitivity is around 70% with a much higher specificity, compared with PCR test sensitivity of >95%.

In an ED setting, ease of testing and rapid results are key attributes, although the need for results in 15 minutes is debatable when many patients are in EDs for longer time periods before being admitted.

When considering the range of tests (Table 1), the assay sensitivity and specificity is critical. The sensitivity of a test refers to a true positive result; the number of people correctly found to be infected. A test with high sensitivity is key to identify as many people infected as possible and reduce the false negative number.

Test specificity is a true negative result; the number of people found not to be infected. Therefore, high specificity reduces the number of false positive results. Ideally, the most accurate test would have a high sensitivity and specificity.

The cycle threshold (Ct) value in a PCR test is the number of PCR amplification cycles leading to NA detection that breaks the threshold value of fluorescence, where fluorescence demonstrates NA detection. It is a semi-quantitative marker of the amount of NA and a low Ct value, i.e. 10 cycles, is consistent with higher viral loads and a higher Ct, i.e. 30 cycles, is consistent with lower viral loads. The latter would mean the infection is less transmissible assuming an adequately collected swab sample.

During the COVID-19 pandemic, Hiroi et al reported that SARS-CoV-2 was isolated from saliva samples 9% of times in cell culture (positive culture being indicative of infectious virus) when the Ct was 35-40.6

A visual read out of the result with the Ct value and the shape of the sigmoid curve is helpful as some assay software systems may interpret a result as negative based on the test algorithm set by the manufacturer. For example, a Ct value of 34 may be set as the cut-off and therefore a Ct of 35 may be reported by the machine as negative, despite the presence of a sigmoid curve, which is typically representative of effective PCR amplification.7

TABLE 1: ASSAY COMPARISONS

	Lateral flow device	Isothermal technologies	Cartridge-based PCR systems	PCR systems
Detects	Antigen	Nucleic acid	Nucleic acid	Nucleic acid
POC or laboratory-based	POC	POC / Laboratory	POC / Laboratory	Laboratory
Time to result	15 minutes	6-15 minutes	30-60 minutes	2-5 hours
Relative sensitivity	Lower	High	Higher	Higher
Ease of use	Easy	More manipulation	More manipulation	More manipulation
Cost	Low	Low	Higher	Higher
Ct value and amplification curve	No	Yes in some	Yes in some	Yes
Line visible	Yes	Yes in some	No	No

There are a range of commercial respiratory virus PCR tests that can test for 1-4 viruses or 8 or more viruses in cartridge-based stand-alone equipment or involving a larger machine that can take 2-5 hours to report the result. There are single and multiple, M-LFD, antigen detection tests as well as isothermal technologies such as loop mediated isothermal amplification (LAMP), recombinase polymerase amplification (RPA) tests and NEAR Technology (Nicking Enzyme Amplification Reaction).

LAMP methods amplify nucleic acid without an extraction step under isothermal conditions in under an hour. However, non-specific amplification may be found and there is a much higher false negative rate compared to RT-PCR.

A visual read out of the result with the Ct value and the shape of the sigmoid curve is helpful as some assay software systems may interpret a result as negative based on the test algorithm set by the manufacturer.

Batra et al1 reported the results of a large study of individuals attending ED with respiratory symptoms whose respiratory swabs were tested using an LFD assay. The sensitivity of the LFD when compared with PCR was 67% for influenza A, 94.1% for influenza B and 48.2% for SARS-CoV-2.

However, 98% sensitivity was reported where the Ct value was <25. The conclusion was that LFD achieved high sensitivity for individuals with high viral load samples who were most likely to be infectious.

It was acknowledged that the lower sensitivity of LFDs may mean a PCR test was needed in those who were symptomatic with a negative LFD result. However, it was felt that these results would be in a minority.

Similar results were reported by Murphy et al2 Meyer et al and Garcia-Rodriguez3,8 suggested that negative LFD results should be confirmed with nucleic acid testing in patients with respiratory symptoms to prevent nosocomial transmission. Serigstad et al9 demonstrated that PCR results could be reported in a median time of 2.6 hours. Van der Moeren et al10 reported no transmission where the LFD result was false negative but came to that conclusion after analysing whether patients with positive results had shared a room with a patient with a false negative result.

Negative LFD results must be confirmed with nucleic acid testing in patients with respiratory symptoms to prevent nosocomial transmission. Using rapid molecular POCT in triage pathways may reduce the need for confirmatory PCR testing while improving patient flow, treatment decisions and infection control.

These reports demonstrate the need for a less expensive, easy to use and accurate assay, but recognise that, at the moment, only the first two criteria stand. There is a clear transmission risk accepting LFD test results in an individual with influenza A/B or COVID-19 with a swab result reported as negative but then with a positive PCR with a Ct of >25.

STUDY

A local evaluation (presented at the UK Clinical Virology Network conference 2026) was carried out over a 6-week period, that started on November 1 2025, of all respiratory virus PCR assay results that were positive for influenza A, influenza B or SARS-CoV-2 RNA. These were compared with the results of the M-LFD test for influenza A/B and SARS-CoV-2 in the adult and paediatric ED and ward settings for patients with respiratory symptoms.

RESULTS

• 43 patients had M-LFD and PCR tests carried out within 24 hours.
• 79% had false negative M-LFD results and the remainder had concordant positive results.
• 62% of patients with influenza virus infections were diagnosed outside the recommended treatment period and the majority of patients with false negative results were managed in bays or moved between wards before the result was available.

In addition to these concerns, infection control teams need to be aware that assay sensitivity can vary. The UK Health Security Agency (UKHSA) evaluation of 86 SARS-CoV-2 LFDs reported assay sensitivity ranging from 32-83%.11 There was no correlation seen between manufacturer-reported test sensitivity and UKHSA determined test sensitivity nor between manufacturer-reported test limit of detection and UKHSA-determined test sensitivity.

The timing of diagnostic testing is key as patients with lower viral loads may still be infectious, especially in the early stages of infection, while PCR tests may remain positive, detecting residual nucleic acid, weeks after infection when the individuals are highly unlikely to be infectious.12 In these circumstances, culturing virus to show it is actively replicating or detecting mRNA is the only way to show potential transmissibility but is labour intensive and takes several days to weeks. Therefore, POCT and PCR test results must be interpreted carefully, taking into account the clinical details when considering infection control measures and antiviral management.

In December 2025, the median wait time for patients in EDs in the NHS before being admitted was 4 hours and 36 minutes.13 This means there would be sufficient time to run a cartridge-based PCR on-site. There are numerous reports demonstrating their levels of sensitivity that are reassuring.14-16

 

Future technology includes quantum dot nanobead-based multiplex fluorescence lateral flow immunoassay biosensors with a low limit of detection of around 41 copies/mL,17 results within 20 minutes, together with good reproducibility and accuracy.

Amat et al18 evaluated a pan-viral host biomarker, CXCL10, a cytokine induced in the nasal mucosa in response to respiratory virus infection that accurately predicted a positive virus result.

POCT and PCR test results must be interpreted carefully, taking into account the clinical details when considering infection control measures and antiviral management.

In conclusion, the most pragmatic approach for patients with respiratory symptoms involves an LFD POCT or a more sensitive isothermal POCT at triage and an immediate PCR test if either result is negative.

REFERENCES

1. Batra R et al. Emerg Med J 2025;0:1–7.
2. Murphy C et al. Diagnostic Microbiology and Infectious Disease 2024;110:116421.
3. Meyer J et al. Journal of Medical Virology 2025;97:e70493.
4. Mojebi A et al. PLoS One. 2024 Jun 13;19(6):e0303560.
5. Clark TW et al. J Infect. 2023 May;86(5):462–475.
6. Hiroi S et al. J Med Viro. 2021;93:5917–5923.
7. Zuckerman M et al. J Infect Dis 2024;230(6):1299–1301.
8. Garcia-Rodriguez J et al. Microorganisms. 2025;13:63.
9. Serigstad S et al. Sci Rep. 2022;12:326.
10. Van der Moeren et al. Clin Microbiol Infect. 2023;29:1595–1599.
11. Kulasegaran-Shylini R et al. eClinicalMedicine. 2025;87:103454.
12. Korenkov N et al. Journal of Clinical Microbiology 2021;59:00896–00821.
13. Nuffield Trust. A&E waiting times. Available at: https://www.nuffieldtrust.org.uk/resource/a-e-waiting-times (Last accessed June 2026).
14. Ledda C et al. Biosensors and Bioelectronics: X 2025;27:100691.
15. Banerjee D et al. J Clin Viro. 2026;182:105902.
16. Gonzalez K et al. J Clin Micro. 2025;63:10.1128/jcm.00708-25.
17. Li X et al. Front Immunol. 2025;16:1540676.
18. Amat J et al. eBioMedicine. 2025;117:105820.

Abbreviations: PCR - Polymerase chain reaction. POC - point of care. Ct - cycle threshold.

Disclaimer: This content has been supported by Abbott Rapid Diagnostics, Infectious Diseases as part of a sponsored advertorial. The views expressed are those of the authors who have not received financial remuneration for writing this article.

RDx-26001668 | 05/26