Modern screening methods are designed to rapidly identify a sample as either negative or presumptive positive if the substance is above a set cut-off concentration. Negative samples are deemed to not require further investigation, whilst samples that are presumed to be positive will require testing by a different analytical technique, known as a confirmation test.
Our screening methods are based on established immunoassay technology and can be conducted in a laboratory or with a rapid diagnostic test at the point of care. Immunoassays utilise antibodies as reagents to measure the amount of a particular drug or drug group in the sample.
Antibodies bind to the drug by recognising a distinct three dimensional shape. In simplest terms this can be thought of as a key in a lock. The key (drug) has a distinct shape which will only fit into a suitably matched lock (antibody). This concept is shown in figure 1, where each coloured block is a different drug (with a different shape) reacting to a matching antibody.
Figure 1: A stylised representation of three antibodies recognising three different shapes. Notice that each shape will only bind to one antibody.
A confirmation test is able to definitively detect individual compounds by matching them to a commercially prepared reference standard. Confirmation tests provide qualitative results of drugs and/or drug metabolites present in the sample.