Many areas of medicine, food processing, industrial processing and farming require the ability to detect the presence of a particular material. The need to measure the drug or other substance may be as a result of the abuse of drugs, the monitoring of therapeutic dosage, the detection of a pathogen, the detection of a diseased state, such as neoplasia, the detection of contaminants or pollutants, or the concentration of a particular component, as illustrative of the many situations which may be involved.
There has been an increasing interest to remove the requirement to measure a substance in the clinical laboratory and to measure the substance at the site where the information is to be used. This may include the doctors office, the home, the farm, the field or the processing plant. In this situation, there are many restrictions on the nature of the manner in which the determination is to be carried out. For the most part, the devices must be simple, rugged, and easily handled. The protocols should also be simple, and involve a minimal number of measurements of sample and reagent, preferably zero, minimal handling and number of reagents, as well as a small number of steps. In addition, the results should be easy to read, particularly being visually determined. In addition, there are other considerations such as preventing aerosolization, providing reagent stability, and the like.
The design of such devices therefore requires efforts to optimize the various requirements, without unduly interfering with other requirements. Thus, as a practical matter, the devices are only difficultly conceived and reduced to practice.