What is Immunoassay antibody testing?
A marker, known as the antigen, is selected to target the microorganism in question. It is usually a part of the microorganism or a chemical they produce during their growth.
An antibody is developed to bind to a specific antigen. The antibody-antigen combination is unique as the two fit together like jigsaw pieces.
Antibodies or antigens can be attached to surfaces and used to collect and measure the amount of organism present in a sample. The collected antigen is used to confirm whether the organism is present and determine the approximate quantity of it. This is a common tool for detecting levels of specific chemicals in clinical settings for medical diagnosis. For example, it is used to precisely measure blood insulin levels to check for hypoglycaemia, hormones for prostate cancer or drugs used in sports doping.
Immunoassay antibody testing is used all over the world and is being especially highlighted now as we use it for covid-19 testing. This important technology has a huge market, with millions of tests being done daily for corona-virus worldwide.
| Immunoassay – a biochemical test that measures the amount of a specific substance with antibodies and antigens. |
| Antigen – a specific marker for the organism. |
| Antibody – a binding protein that attaches to its specific antigen. |
| Competition assay – the antigen in the sample competes with the antigen on the test line for binding. |
We have developed antigens that are used as markers for key microorganisms known to contaminate fuel. These are grouped into three categories for detection by the test kit:
- Bacteria
- Fungi – yeasts and moulds
- H.res (Hormoconis resinae) – a filamentous fungi particularly prevalent and problematic in fuel
FUELSTAT® test plates contain 6 tests, testing for each separate group at high (heavy contamination) and low (moderate contamination) levels as per the IATA guidance material . Testing each separate group at two levels allows us to determine the type and severity of contamination present in the fuel, when both tests are negative a negligible level of contamination is recorded.
FUELSTAT® uses a “competition assay” type test:
- The blue reagent is used to extract the antigens in the sample.
- This is then applied onto the lateral flow device (LFD) and mixes with our antibodies that are specially designed to bind the antigens of fuel degrading microorganisms. These antibodies have been labelled with a gold dye that has a red colour.
- The liquid will soak into the enclosed pad and the mixture of dyed antibodies and antigens will flow along the device.
- On the device there is a test line “T”, this has a known quantity of antigen embedded in it. The dyed antibodies bind to the antigen in the sample first, then any leftover unbound dyed antibodies will bind to the test line.
Positive
Negative
There is more antigen in the sample than on the test line. The sample antigen binds all the dyed antibodies and none is left to bind to the test line. There is less antigen in the sample than on the test line. There are plenty of dyed antibodies left to bind to the test line. A red test “T” line is NOT formed A red test “T” line is formed
- There are two thresholds of test on each kit for each of the 3 detected contamination groups. The “low” side of the test will show a positive (no line) when moderate levels of contamination are present, the “high” side will show a positive (no line) with a heavy contamination. When all six of the tests on the plate give negative results (all “T” lines visible) it shows negligible levels of contamination.
- To verify validity of the test and ensure that there is sufficient reagent flow along the test strip there is a built-in control line “C”. When the reagent flow reaches that point a strong line should appear on all tests to indicate proper flow.
The FUELSTAT® test kit plate
What advantages does FUELSTAT® technology give me?
FUELSTAT® identifies the presence of microorganisms known to contaminate and degrade fuel by detecting their antigens. Antigens act as markers that can be assessed using immunoassay antibody tests. Immunoassay antibody technology is specific which allows FUELSTAT® to only identify the presence of fuel degrading microorganisms; other types, such as those that may be found on humans and the surrounding environment and could easily contaminate a test, will not be detected. Sterility and cross-contamination of tests is therefore less of an issue than other techniques.
FUELSTAT® will give results as negligible, moderate, or heavy level of contamination, reflecting IATA guidelines [1]. Each group of organisms; bacteria, fungi (moulds and yeasts) and H.res are tested on high and low LFD assays, giving a clear picture as to which group of microorganisms are present in the fuel and the level of contamination. Detailed test procedure can be found at reference [2].
Immunoassay antibody tests are inherently quick, simple and reliable. This technology is prepared and enclosed in the plate allowing the test to be done in 15 minutes, on site and with minimal training. By measuring the presence and intensity of test lines, the FUELSTAT® app is available to help read the tests, record and communicate data, so that work can be done in solo conditions and multiple locations.
[1] The International Air Transport Association (IATA): Guidance Material on Microbiological Contamination in Aircraft Fuel Tanks, 5th Edition
[2] International Standard ASTM D8070 details the standard test method for screening of fuels and fuel associated aqueous specimens for microbial contamination by lateral flow immunoassay.
