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All You Need To Know About In Vitro Diagnostic COVID-19 Tests

The Diagnostic Test Development And Evaluation

The in-vitro diagnostic test has remained relevant since a long while. The pharmaceutical industry has often not paid enough heed to the realities that are responsible for the evolution and progress of this in-vitro diagnostic tests. The evolutions of this test are also called the performance characteristics. This happens to be the best time for in-vitro diagnostics. With the Coronavirus pandemic bringing a completely unexpected opportunity to showcase the actual perks of diagnostics in the modern world. The performance characteristics of this diagnostic test can be categorised in three ways:

1. The Analytical Validation

The first most important thing to check is whether the device is actually working as described and if it’s made properly. This validation also includes checking the materials and reagents that should be consistent and of the highest quality in every batch. All the devices in each batch should be reliable. There are other more important questions in this regard as well, like do various users arrive at the same results when using the same samples? Where does the device actually work at it’s best? Does the person who uses it needs special training? If the device is able to count the numbers of an analyte, how accurate can it detect the analyte level? Which samples can provide the most reliable result, and how should they be transported? Lastly, are there any other materials and components that should be considered that might hinder the test results? It should be noted that SARS- CoV-2 is very much like other coronaviruses, at the RNA level and also because some of the proteins in the capsid are the same. Majority of the various Covid-19 tests that are done in the development phase have some degree of validation. However, this might not be on the standards that one might expect. Another important thing to understand is that the tests labelled as CE-marked sometimes do not have any third-party scrutiny and checks.

2. Clinical Validation

The clinical validation is generally shown in terms of sensitivity and has to be very accurate. In all the true positive samples that are called positive after the test, sensitivity is taken into account. Moreover, specificity over here is noted for all the true negative samples that are labelled negative after the test. A lot of tests are termed as highly sensitive and specific, sometimes even as high as 99%. However, it should be noted that the sensitivities and specificities of these samples cannot be absolute. Important things often not mentioned in the literature of a test are, “which samples were used as true positives and true negatives?” and “how was it determined that the test was positive or negative?” if the researcher is unable to determine the nature of the validation samples, they cannot interpret the sensitivities and specificities. For instance, when the Covid-19 antibody tests were conducted in the start, validation samples were taken of patients who had experienced severe illness. These samples were taken when the patient’s IgG response was highest and the samples showed high levels of the antibody with the help of several serological techniques. The data is still not very clear and explainable, but apparently, some patients did not develop the antibody response while those that did, generated IgM in approximately 10 days after the infection and IgG or IgA a few days later.

3. Clinical Utility

This happens to be one of the most important matters that is often overlooked. Unfortunately, doctors and researchers are still not able to fully understand Covid-19, and this is why the meaningfulness of results can be argued upon despite the results being accurate. Therefore, specific SARS- Cov2 RNA can be detected from the throat, as well as nasopharyngeal swabs, but this needs to be done very carefully. Detection definitely means that the subject did come in contact with the virus, but if symptoms aren’t fully appearing, the question remains as to if they will develop an illness or not. Tests that have sensitivity and specificity of more than 90% can be counted as useful, especially when the object has more true positives. For the antibody test to ascertain if the patient has fully recovered and is immune, the highest specificity level is needed for safety. (Holland &Bagshaw, 2020)
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Holland, R., &Bagshaw, J. (2020). What you need to know about Covid-19 testing. Faculty of Pharmaceutical Medicine.

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