Analyses for antibodies against the novel coronavirus SARS-CoV-2 are subject to many uncertainties as well as numerous dubious offers for home testing, which can produce false results. That’s why in this document, we address important aspects of the COVID-19 antibody analysis technologies and explain what Novogenia offers and in what form.
The antibody analyses can be classified into three different approaches:
THE QUICK TEST FOR AT HOME
In this procedure, analysis kits, which resemble a pregnancy test, are purchased by laypersons via the Internet and carried out at home with a lancet and a fingertip prick. The testing person is not trained, and the analysis is not performed in a controlled laboratory environment. There are more than 100 manufacturers for these kits. Most of them do not have European CE IVD approval, and their quality is highly questionable.
With this approach, the risk of incorrect application is very high. Moreover, without experience in evaluation and professional laboratory equipment, the review is very error-prone. It is therefore generally not advisable to use these rapid tests at home.
ANTIBODY TEST IN THE LABORATORY (LATERAL FLOW METHOD)
In this procedure, blood is taken from the patient and sent to the laboratory.
The collection can be carried out either by a doctor from the vein or by the patient himself with a fingertip prick. In the laboratory, the blood sample is first converted to the serum by a laboratory device, as this is more suitable for analysis than whole blood.
The serum is then evaluated on lateral flow analysis systems. Optically, this is similar to the analysis with a quick test for home use, which shows lines in case of detected antibodies.
The test kits used for the analysis must meet some criteria
- They must be CE-IVD certified. This means that the effectiveness of the tests
- Has been proven in advance in functional studies.
- They must have been verified for functionality in the laboratory before they are used in clinical applications.
- Theymustbeevaluatedbytrainedpersonneltrainedinnaturalsciencesinacontrolledlaboratory environment.
- The laboratory must comply with Biosafety Level 2 to work with viral material.
- A second analysis of technology must verify unclear results.
For professional use, this form of analysis is very accurate and suitable for antibody testing.
ELISA TEST IN THE LABORATORY
With this technology, blood samples are also taken and sent to the laboratory. The analysis is performed by trained personnel with specialized equipment. A few manufacturers only produce the reagents used. Also, they are currently not available in sufficient quantities, but this will probably improve in the coming weeks and months.
In this procedure, the antibodies are attached to individual ELISA plates and then stained. The darker the color, the higher the antibody concentration in the examined sample. Due to the quantitative measurement, the ELISA test offers a higher accuracy compared to the Lateral Flow Method.
The right time for antibody analysis
For a meaningful result, it is essential to use antibody analysis at the right time. While a PCR analysis can identify the viruses very early and before symptoms appear, antibody analyses only make sense in the later sale of the disease.
An antibody test used too early is just as likely to give a false negative result as a PCR test used too late. Therefore, the right timing is crucial for the reliability of the test results.
The antibody analyses of Novogenia
have proven to be highly reliable in our internal comparison of different suppliers.
Each positive result is then analytically confirmed by a further procedure using a CE- IVD-certified
test kit to increase the significance further (sensitivity). The result is a laboratory chemical report that
precisely describes the analytical results as well as the significance and limitations of the analysis.
Does the analysis erroneously detect other antibodies?
With the reagents of some manufacturers, there is socalled cross reactivity. This means that the system may
detect antibodies against a similar virus and thus provide a
false-positive result. For this reason, the analytical method
used must react exclusively to antibodies against SARSCoV-2.
The system used by Novogenia was tested for crossreactivity against the virus antibodies shown in the table
on the left.
- Parainfluenza virus antibody
- Influenza A antibody
- Influenza B antibody
- Chlamydia pneumonia antibody
- Adenovirus antibody
- Respiratory syncytial virus antibody
- Treponema pallidum antibody
- HIV antibody
- EB virus antibody
- Measles virus antibody
- Cytomegalovirus antibody
- Enterovirus type 71 antibody
- Mumps antibody
- Varicella-Zoster virus positive sample
The analysis system does not recognize antibodies against
the aforementioned common viruses as false-positive
Do drugs influence the significance of the analysis?
Certain drugs can influence the mode of action of an analysis system. For this reason, it is essential to
test an antibody analysis for interferences.
The following commonly used drugs were tested:
None of the drugs showed any influence on the analytical reactivity of the system.
During validation, 596 clinical samples from 361 confirmed positives and 235 confirmed negative
patients were analyzed.
|Wondfo SARS-CoV-2 Antibody Test (Lateral Flow Method)||Positive|
as healthy by negative SARS-CoV-2 PCR analyses.
The validation brought the following result:
Positive result (sensitivity):
Significance 86.43% (95%CI: 82.41%-89.58%)
Negative result (specificity):
Significance 99.57% (95%CI: 89.10%-93.58%)
Expected from May 2020 at Novogenia: ELISA-Confirmation of positive samples
Currently, all positive results are confirmed by two different analysis systems. From May onwards, we
will probably have even better analysis systems at our disposal, with sensitivity perhaps rising to more
than 95%. Positive samples are then confirmed by Novogenia’s ELISA system and reported as
laboratory chemistry results.
The sample material
Whole blood in heparin or Li-Heparin is suitable as sample material.
This can be taken from the vein and transmitted to Novogenia. Blood samples collected with a lancet from the fingertip can be made by the patient himself and also give good results. Blood samples are stable at room temperature for up to seven days.
The laboratory capacity for antibody analysis
An antibody analysis consists of three essential steps, which have different personnel requirements.
1) Centrifugation for serum generation
With a centrifuge with 24 places and 30 seconds each for loading and unloading as well as a threeminute centrifugation step, one person can process 2,880 samples in an eight-hour shift. One person
can operate three centrifuges in parallel and thus achieve a capacity of 8,640 samples in one eighthour shift.
2) Apply to Lateral Flow Analysis Kit
10µl of the serum must be applied to a test strip. After the application, a 100µl buffer solution is added. The strip then needs 15 minutes to form the result. Loading per piece takes 13 seconds. Until the first loaded test delivers the final result, 70 tests per person can be loaded. In an eight-hour shift, one person can thus process 2,240 samples so that a total of 6,720 samples per day can be processed in a three-shift operation.
3) Evaluation and registration in the laboratory management system
The result must be read after 15 minutes and registered in the system. Each evaluation and registration
via a barcode reader takes six seconds. One person can thus process 4,800 samples per shift.
5,600 samples per day possible
Taking into account the specified times and capacities, approximately 5,600 antibody tests can be evaluated (including a twenty percent positive and duplicate test rate) with nine persons per day.
Once ELISA analyses are established in our laboratory, they can be processed by one of our six liquid handling robots (Qiagen Biorobot Universal). The capacity here is also around 5,600 samples per day.