Evaluating the Best COVID-19 Testing Kits:
A Detailed Analysis
The ongoing threat of respiratory infections has necessitated the development of rapid, reliable
diagnostic tests that can distinguish between common culprits like influenza and the novel
coronavirus, SARS-CoV-2. This article delves into a comparative analysis of several prominent
diagnostic tools, with a particular focus on the CorDx TyFast Flu A/B & COVID-19 Multiplex
Rapid Test, a standout in the field.
CorDx TyFast Flu A/B & COVID-19 Multiplex Rapid Test
Overview
The CorDx TyFast Flu A/B & COVID-19 Multiplex Rapid Test distributed by Cost Plus Med
Tech is a lateral flow immunochromatographic assay designed for the simultaneous qualitative
detection and differentiation of influenza A, influenza B, and SARS-CoV-2 nucleoprotein
antigens. This test is authorized for use in point-of-care settings, including those operating under
a CLIA Certificate of Waiver, Certificate of Compliance, or Certificate of Accreditation.
Key Features
Sample Type

Anterior Nasal Swab: The test uses anterior nasal swab specimens, which are less
invasive and easier to collect compared to nasopharyngeal swabs.
Detection

Multi-Pathogen Detection: It differentiates between influenza A, influenza B, and
SARS-CoV-2 nucleoprotein antigens, making it a comprehensive tool for respiratory
infection diagnosis.
Users

Symptomatic Individuals: This test is intended for use within the first five days of
symptom onset for individuals showing signs of respiratory infection.
Accuracy & Sensitivity
The CorDx TyFast Flu A/B & COVID-19 Multiplex Rapid Test boasts high sensitivity and
specificity, ensuring reliable detection even at low viral loads. Clinical studies have
demonstrated a Positive Percent Agreement (PPA) of 89.1% for SARS-CoV-2, 83.6% for
influenza A, and 90.0% for influenza B. The Negative Percent Agreement (NPA) is 99.8% for
SARS-CoV-2, 98.8% for influenza A, and 99.9% for influenza B.
Usability
Designed for ease of use in healthcare settings, the test includes clear instructions and built-in
procedural controls to guide users through the testing process. While the need for professional
supervision reduces the potential for user error, the test remains straightforward with a quick
turnaround time of about ten minutes.
Comprehensive Detection
The ability to simultaneously detect and differentiate between multiple pathogens sets the CorDx
TyFast Flu A/B & COVID-19 Multiplex Rapid Test apart. This multiplexing capability
streamlines the diagnostic process, allowing for quicker and more comprehensive treatment
decisions.
Regulatory and Safety Notes
The CorDx TyFast Flu A/B & COVID-19 Multiplex Rapid Test is authorized under
the FDA's Emergency Use Authorization (EUA), ensuring it meets stringent criteria for safety
and effectiveness. Its use is limited to laboratories certified under the Clinical Laboratory
Improvement Amendments of 1988 (CLIA).
Practical Considerations
Ease of Use

Designed for healthcare providers but also suitable for point-of-care settings.
Multiple Targets

Simultaneously detects influenza A, influenza B, and SARS-CoV-2, offering a more
comprehensive diagnostic tool.
Reliability

Higher sensitivity and specificity reduce the likelihood of false negatives and false
positives, ensuring more reliable results.
Flowflex COVID-19 and Flu A/B Home Test
Overview
The Flowflex COVID-19 and Flu A/B Home Test is a rapid antigen test designed for the
qualitative detection and differentiation of SARS-CoV-2, influenza A, and influenza B protein
antigens. It is intended for non-prescription home use, allowing individuals to self-collect
anterior nasal swab specimens.
Key Features
Sample Type

Anterior Nasal Swab: Similar to the CorDx test, it uses less invasive nasal swabs.
Detection

Antigen Detection: Identifies viral proteins for SARS-CoV-2, influenza A, and B.
Users

Home Use: Designed for individuals aged 14 years or older to self-collect samples, while
children aged 2-13 years should be tested by an adult.
Accuracy & Sensitivity
While Flowflex claims high sensitivity for detecting SARS-CoV-2, influenza A, and B, its
accuracy can vary based on user technique and adherence to instructions. The test has a higher
chance of false-negative results, especially with low viral loads.
Usability
The test is designed for ease of use at home, with straightforward instructions and simple
handling. However, user error in sample collection or interpretation can affect the results.
Speed of Results
Flowflex provides results in approximately 15 minutes, making it a quick option for home
testing.
Cost and Availability
Available over-the-counter and can be purchased at various retail locations or online, making it
easily accessible for home users.
CLINITEST Rapid COVID-19 Antigen Self-Test
Overview
The CLINITEST Rapid COVID-19 Antigen Self-Test by Siemens Healthineers is designed
for the rapid detection of SARS-CoV-2 antigens in anterior nasal swab samples. It is primarily
intended for self-administration by individuals aged 14 years or older.
Key Features
Sample Type

Anterior Nasal Swab: Ensures a less invasive specimen collection method.
Detection

SARS-CoV-2 Nucleocapsid Protein Antigen: Targets the viral nucleocapsid protein.
Users

Symptomatic and Asymptomatic Individuals: Suitable for individuals who suspect
they may have COVID-19.
Accuracy & Sensitivity
The CLINITEST claims a PPA of 85.4% and an NPA of 99.3%, suggesting a high level of
specificity. However, the sensitivity may not be as reliable for detecting lower viral loads, which
can result in false negatives.
Usability
Designed for home use, the test requires users to follow a series of steps involving swabbing,
inserting the swab into a tube with a reagent, and applying drops onto a test device. The result is
read after 15 minutes.
Regulatory and Safety Notes
The CLINITEST is authorized under the FDA Emergency Use Authorization (EUA), ensuring
it meets safety and effectiveness criteria. However, results can be user-dependent, with incorrect
swabbing or reading potentially leading to false results.
InBios Rapid Test
Overview
The InBios Rapid Test is a lateral flow immunochromatographic assay designed for the
qualitative detection of the SARS-CoV-2 nucleocapsid protein antigen in anterior nasal swab
specimens. This test is primarily intended for symptomatic individuals. A Complete review and
comparison of this test can be found here: Inbios Covid Test vs. CorDx.
Key Features
Sample Type

Anterior Nasal Swab: Utilizes less invasive swabs for specimen collection.
Detection

SARS-CoV-2 Nucleocapsid Protein Antigen: Targets the specific viral antigen.
Users

Symptomatic Individuals: Mainly intended for those showing COVID-19 symptoms.
Accuracy & Sensitivity
The InBios Rapid Test has shown a PPA of 84.2% and an NPA of 99.8%, indicating high
specificity but limited sensitivity. This means the test is effective at identifying non-infected
individuals but less reliable in accurately identifying infected ones.
Usability
It is designed for ease of use in various settings, including physician offices and school health
clinics. The test provides quick visual results within approximately 20 minutes.
Limitations
Despite its advantages, the InBios Rapid Test has several limitations, including:


Limited Sensitivity: Higher chance of false negatives, especially in low viral load
scenarios.
Single Pathogen Detection: Limited to detecting only SARS-CoV-2, restricting its
utility in differentiating between other respiratory infections.
Conclusion
When evaluating the best COVID-19 testing kits, the CorDx TyFast Flu A/B & COVID-19
Multiplex Rapid Test stands out as one of the best options available. Its ability to
simultaneously detect and differentiate between influenza A, influenza B, and SARS-CoV-2,
coupled with high sensitivity and specificity, makes it an indispensable tool in both clinical and
point-of-care settings.
Other tests such as Flowflex, CLINITEST, and InBios Rapid Test offer valuable diagnostic
solutions but come with limitations in terms of sensitivity, ease of use, and scope of detection. In
the ever-evolving landscape of respiratory diagnostics, the CorDx TyFast Flu A/B & COVID-
19 Multiplex Rapid Test emerges as a frontrunner, providing healthcare professionals with a
dependable tool for managing and controlling the spread of infectious diseases.