Covid-19 serological test

WHAT ARE THE COVID-19 SEROLOGICAL TESTS USED FOR?

The serological tests are used to highlight the presence of direct antibodies fighting a virus, in this case the SARS CoV 2 virus responsible for Covid-19.

Their presence may indicate that you have been exposed to the virus, but a positive antibody test does not guarantee that you are immune to coronavirus. At the moment, the protective titre of the antibodies and their duration in time are not known. The absence of antibodies does not rule out the possibility of an infection at an early stage or without symptoms, with the consequent risk of being contagious.

The serological test does not replace the search for viral RNA using the molecular technique (through a nose and throat swab) that, for the time being, is the only conclusively diagnostic test.

WHICH TYPE OF TEST IS PERFORMED AT AUXOLOGICO?

Individuals have available the ECLIA quantitative serological test for Total Ig that provides the response about the presence or absence of both IgG and IgM immunoglobulin classes at the same time, with 99.81% specificity and sensitivity above 95%.

Antibody kinetics of the Covid-19 infection is currently under study. Not only it exhibits anomalies relative to standard criteria, but also almost concurrent appearance of the different antibody classes was observed.
Therefore, the early diagnostic approach should not be limited to the search for IgM, but rather to the search for viral RNA. Similarly, the immune defence determined by IgG presence is still to be further investigated. Also, the IgG protection titre and duration in time are still uncertain.
Therefore, simultaneous cumulative measure of antibody classes (Total Ig) is the most suitable test to study infection prevalence.

Corporate clients may also opt for the rapid test (qualitative) that is available after contacting Auxologico’s Agreements Service (convenzioni-mi@auxologico.it ).

It is important that you know that:

• IgM are the first antibodies to be produced in response to an infection; consequently, their being present indicates a recently developed infection;
• IgG are produced later and normally provide the memory and immune defence.

However, you should remember that Covid-19 antibody kinetics is still being studied and is proving anomalous relative to standard criteria.
The memory and consequent immune defence determined by IgG presence as well as their protection titre and duration in time are still to be further investigated.

HOW IS THE TEST PERFORMED? 

The ECLIA quantitative serological test is performed by means of a venous blood taking.

The test can be taken also in the afternoon. Strict fasting is not required. Also, no special preparation is required, but it is recommended that you wait a couple of hours after a light meal before blood taking.

WHO IS RECOMMENDED TO TAKE THE SEROLOGICAL TEST?

All people who were not already confirmed positive by means of a swab and suspect they may have contracted the infection.

The serological test for screening purposes is always taken on a voluntary basis (this applies also when screening is promoted by corporate clients and is agreed upon with the company appointed physician).

The results of the serological test and swab, if any, will be notified to the ATS of patient’s place of residence and/or to the company appointed physician, in accordance with the directions provided by the regional authorities; the patient’s personal and contact data will be supplied.

WHEN YOU CANNOT TAKE A SEROLOGICAL TEST?

You must not enter the facility and, consequently, the phlebotomy room in the following cases:

• Your temperature is 37.5°C or higher;
• You suffer from suspected or confirmed COVID19 disease;
• You have shown unusual symptoms suggesting COVID in the last 2 weeks such as: fever, dry cough, fatigue, headache, muscle and joint pains, nasal congestion, nausea, diarrhoea, sore throat, conjunctivitis, loss or change in the sense of smell or taste. 

If you have any of the above conditions, postpone your appointment.

WHAT DOES THE SEROLOGICAL TEST RESULT SAY?

• NEGATIVE

A negative test result indicates that you have not been infected or have been infected very recently (less than 8-10 days before being tested) and have not yet developed the antibody response to the virus or you have been infected but the antibody titre you have developed is below the test detection level at the time of testing.

• POSITIVE

A positive test result indicates that you have been infected, but it does not necessarily indicate if your antibodies are neutralizing (i.e. if you are protected and if so, for how long) or if you have recovered or are still contagious. Therefore, it is necessary to perform the molecular test from a nose and throat swab to search for viral RNA.

READING SEROLOGICAL TEST RESULTS

WHAT HAPPENS AFTER A POSITIVE ANTIBODY TEST?

You will be contacted to fix an appointment to get a nose and throat swab for the search of viral RNA at the charge of the Regional Health Service. This procedure is required to rule out the presence of the virus and associated risks of contagion.

You will be swabbed at Auxologico free of charge within a few days from the positive serological test result.

Waiting to be swabbed, you must: 

• Observe self-isolation at home;
• Immediately inform your General Practitioner of the positive serological test result.

If the swab is negative and you show no symptoms, you can discontinue self-isolation and return to social life.

If the swab gives a positive result, you must immediately inform your GP, observe self-isolation at home and remain quarantined in the times and modes as instructed and in any case until negativisation that will be assessed not earlier than 10 days from the appearance of positivity (swabbing day) and after minimum 3 days without symptoms. Swabbing details are to be agreed upon with your GP.

CORONAVIRUS SWAB: HOW DOES IT WORK? ARE THERE ANY ALTERNATIVES?