There are a number of reasons for requesting tests as part of a health assessment for specific or general antibodies, or antigens, in the blood. It is a subject that creates confusion, but the principles are fairly straightforward.
The level of antibodies in a blood sample is measured and expressed as either a titre (or concentration) OR expressed as whole units on a normal or molecular scale... The antibody levels rise in the blood when you have been exposed to an antigen (that is a potential invading organism - or sometimes something that the body thinks is foreign). These antibodies attack and remove foreign substances, or cause harm if the object of the antibody assault is your own tissues.
The antibody titre result can answer one of a number of questions - depending upon the clinical scenario:
The strength of an immune response to the body's own tissue in conditions where the body attacks itself – known as autoimmune disorders Whether a booster injection is required following an immunisation course Whether a previous immunisation course is helping your immune system to protect you against the specific disease. To check if you have currently active disease caused by a specific organism. To check if you have had a previous infection caused by a specific organism.
INTERPRETATION OF RESULTS
What constitutes a normal range depends upon the antibody being tested.
If the test is being carried out to look for antibodies against your own body, the normal value would be expected to be very low If the test is being done to see if an immunisation programme has been successful, the antibody count would be expected to be higher - demonstrating that protection is in place against invasion by that organism Looking for evidence of infection from particular organisms, negative antibody tests can help rule out certain infections whereas a rising titre would suggest infection – either current or past
DIFFERENT CLASSES OF ANTIBODIES
Within any group of antibodies that confer protection (or potential destruction of one’s own tissues) there are different types – knowing which type of antibody present can help differentiate between current or past infection, and active or quiet disease.
When requesting tests for certain viruses, it is essential that the laboratory knows what question is needed to be answered. Broadly speaking, is the problem one of possible infection at some point, a question of immunity or not, or whether there is an autoimmune disease or not?
TESTING FOR INFECTION
This is when things can get tricky. Through Healthscreening.co.uk, dozens of tests of viral or bacterial activity are available. Don’t worry if you not entirely sure what it is that you want to be tested – we can help. It is important that we know the question to be answered, and that you let us know any useful background information – unless of course you have already done your homework and know exactly what test or tests you wish to order. It is important also to realise that not all infections will show positive results immediately – and this will vary between organisms and the tests applied. If you are uncertain, ask us. As a rough guide, antibodies can take quite a long time to show their presence in the blood so if there is any urgency PCR testing may be desired – this type of testing detects the presence of a virus in the blood within days of any infection
Commonly requested tests for active infection include:
Hepatitis B status – specific testing of various classes of antibody, antigen or virus (viral load) can reveal whether there is an infection, and if so, how long it has been present. Testing can differentiate also between those who are carriers or more likely to have complications.
Hepatitis C status – again it is possible to detect active infection by measuring antibody response, antigen presence and viral load.
HIV status – antibody and viral tests are available. The latest PCR tests are can be employed which give reliable results 1-2 weeks after testing. Antibodies may take 6 months to become detectable, however.
Herpes Simplex Type I and II - antibody testing, or the latest PCR testing is available
Lyme disease (Borrelia) – antibody testing
Epstein Barr virus infection – antibody testing
Many more infections can be screened for including a large number of tropical organisms.
TESTING FOR IMMUNITY
You may wish to know whether you have been exposed in the past to a disease-causing organism – and if so, whether you are immune to its effects in the future. This might be necessary for occupational reasons, or to check if your unborn baby is at risk from a disease which you could catch while pregnant. There are multiple antibody tests for immunity available through our sites, although some of the more commonly tested ones include:
Hepatitis B status – usually requested to check that a course of vaccination against the virus has been effective.
Rubella (German measles)
As always, if you need any help to decide which is the most appropriate test for you please let us know.
TESTING FOR AUTOANTIBODIES
Autoantibody screening is often requested if an autoimmune disease is suspected, or just needs to be ruled out. Autoimmune diseases occur when the body makes antibodies to its own tissue – it literally attacks itself. Any organ or tissue can be affected – the thyroid gland, the liver and joint surfaces are examples of many areas that can be attacked. The telltale signs are often found in the blood – and the choice of antibody testing will be determined by symptoms or signs.
Conditions that can be revealed by autoantibody testing include Hashimoto’s and Grave’s disease (thyroid), Rheumatoid arthritis, and Systemic lupus erythematosis (SLE) – and many more. Commonly requested groups of tests include:
Autoantibody screen – thyroid peroxidase antibodies, antinuclear antibodies, mitochondrial antibodies, smooth muscle antibodies, gastric parietal cell antibodies, Reticulin antibodies, anti-liver kidney microsomal antibodies
Connective Tissue Disorder Screen – antinuclear antibodies, anti-dsDNA, antibodies to extractable nuclear antigens, rheumatoid factor, anti-CCP antibodies (plus ancillary tests such as CRP)
Sjogren’s syndrome – anti RO (SSA), anti La (SS-B), salivary duct antibodies
Again – if there is any confusion do ask the clinical team for guidance towards the most appropriate testing for your symptoms or concerns.
No testing is perfect – and testing for antibodies is not without its issues. False-positive results are commonly encountered when testing for autoantibodies in particular – weakly positive readings of antinuclear antibody, for example, are not unusual in perfectly healthy individuals.
The sensitivity of the antinuclear antibody (ANA) test renders it a very useful screening test for systemic lupus erythematosis in particular. Since most people (more than 95% of individuals) with lupus will test positive, a negative ANA test can be helpful in ruling out that condition. However, just over 10% only of those with a positive ANA test have lupus, more have some other autoimmune condition, while up to 15% of completely healthy people have a positive ANA test. Thus a positive ANA test does not automatically translate into a diagnosis of lupus, nor indeed any other autoimmune disease.