Guide to Expert Talk

Guide to the Experts Language

ACCURACY,ANTIBODY, ANTIGEN, BLOOD, BUPRENORPHINE, CONTROL LINE, CUT OFF LEVEL, MONOCLONAL, Ng/ml, NON-NEGATIVE RESULT, POLYCLONAL, QUALITATIVE, QUANTITATIVE, SPECIFICITY, SENSITIVITY, TEST LINE, TIME TO TEST, FALSE NEGATIVES,FALSE POSITIVES, GOLD CONJUGATE, IMMUNOASSAY TEST, LATERAL FLOW, MEMBRANE,METABOLITE

ACCURACY

This is a measure of how good the test is at picking out the antigen. The accuracy is in fact a combination of the specificity and the sensitivity.

ANTIBODY

A special type of protein with excellent detection properties which binds, or attaches to the antigen.

ANTIGEN

The compound that is being detected is called the antigen. It could be a drug, a metabolite, a disease, or it could be the body's own antibody to the disease.

BLOOD

Some tests are based on whole blood, and the cells are filtered out by the membrane. Other tests are based on PLASMA, after the cells have been centrifuged out, or on SERUM after the cells have been removed by clotting.

BUPRENORPHINE

This is a relatively new treatment for heroin abuse.

CONTROL LINE

This is labeled 'C' on most of our tests. It is a stripe that shows the test is working correctly.

CUT OFF LEVEL

The point at which the test is either negative or positive is called the cut off level. For example, the cut off level for Methamphetamine is 300 ng/ml. below this, the test will be negative, and above this the test will be positive. A drug user will have a value in excess of 5 thousand ng/ml, in their urine.

MONOCLONAL

When the antibody is isolated and then manufactured artificially it is known as a monoclonal. The supply of this antibody should be consistent. Well established products are usually monoclonal because they have a better specificity.

Ng/ml

This is a concentration value. One nanogram per millilitre is an abbreviation for 0.000000001 gram per ml

NON-NEGATIVE

The test solution causes the GCAC to travel up the test. In a competitive assay, if there is no drug in the sample, the GCAC binds to the special antibody on the test line. A NEGATIVE result gives A LINE on the TEST line. In a competitive assay, drug forms GCAC which blocks the antibody by binding to it. When the GCAC passes the test line, no further binding takes place, because the antibody is already blocked. A NON-NEGATIVE result gives NO LINE on the TEST line

POLYCLONAL

Antibodies that are extracted from the animal serum without refining are polyclonal. They can be a problem because the supply may not be consistent.

QUALITATIVE

This term refers to any test that gives a positive or negative result. A good way to explain the differences in the two types of tests is to relate to a light in a room. Qualitative tests will look at the light and say whether it is on or off. Quantitative tests will tell you exactly how many lumens are given out and what the spectral range is. For most tests, all you need is a qualitative result.

QUANTITATIVE

This term refers to any test that gives a result with a value. For example a laboratory test may give a figure of 405ng/ml methamphetamine. Quantitative tests are usually used for evidential purposes.

SPECIFICITY

This is a measure of how good the test is at picking out the antigen, without giving any FALSE POSITIVES.

SENSITIVITY

This is a measure of how good the test is at picking out the antigen, without giving any FALSE NEGATIVES.

TEST LINE

This is labeled 'T' on most of our tests. It is a stripe of special antibody that will detect the presence of GCAC.

TIME TO TEST

A NEGATIVE result can be read as soon as a magenta line forms on the test line, which could be a soon as 45 seconds. However, to allow full time for a positive result to develop, the absence of a test line should be read after five minutes.

FALSE NEGATIVES

When a test fails to detect the antigen, it is a false negative. No test can be 100% accurate, but it is best to design the technology for most drug tests to avoid false positives (i.e. have a HIGH SPECIFICITY) so that you do not wrongly accuse someone; and for most medical tests to avoid false negatives (i.e. Have a HIGH SENSITIVITY) so that you do not miss a disease.

FALSE POSITIVES

When a test detects a substance other than the antigen it is designed to detect, it is a false positive. In some cases, however, the test will have detected a product that is very similar to the antigen, such as one of its metabolites.

GOLD CONJUGATE

So that the test result can be seen, very tiny spheres of gold are used to attach the antibody, giving it a purple or 'magenta' colour. The quality of the test is partly due to the uniformity of the conjugate. When it is mixed with the antibody it is called a 'gold conjugate antibody complex', or GCAC.

IMMUNOASSAY TEST

All tests using the antibody technology are called immunoassay because the antibodies are manufactured by an immune system. In a standard immunoassay test, a POSITIVE result produces a line (eg. Pregnancy test). In a competitive assay, a NEGATIVE result gives a magenta line (eg. A drug test)