Biotecnologia Aplicada Elfos Scientiae ISSN: 0684-4551 Vol. 17, Num. 2, 2000, pp. 123

Biotecnología Aplicada 2000;17:123

Near Patient Testing. Technologies and Applications

Gary Thorpe

Wolfson Research Laboratories, Queen Elizabeth Medical Centre, Birmingham, B15 2TH,
England. E-mail: G.H.Thorpe@bham.ac.uk

A number of technological advances are allowing near patient testing (NPT) by inexperienced operators and increasing usage is occurring in clinical chemistry, haematology and microbiological applications. A range of systems is currently available, and more are in development. These include desk-top analysers, small dedicated instruments, and simple disposable non-instrumental systems in which results are interpreted visually [1].

Desk-top analysers are based on either dry chemistry reagent strips or cassettes containing all the liquid reagents required for a test, and several can use whole blood samples, or perform multiple tests simultaneously. Small dedicated inexpensive instruments such as those for blood glucose measurement also have sophisticated features and many of the operator-dependent steps associated with previous systems have been eliminated. Further developments in biosensors, microminiaturisation, the use of reagent arrays such as "DNA chips", and microfluidic integrated circuits offer the extended future application of small analysers, the first application of DNA chips in NPT probably being used for the identification of pathogens and their antimicrobial resistance potencial [2].

One of the key aims of NPT is the development of systems that are either non- or minimally invasive. Most research and development of non invasive and minimally invasive technologies has focused on the development of glucose analysis systems. Systems for glucose analysis are already extremely advanced in comparison to systems for other analytes. These include numerous technologies, ranging from semi-invasive biosensor and iontophoretic approaches to completely non-invasive systems using infrared spectroscopy and light polarisation, which are currently at a variety of development and validation stages for glucose measurement. The successful development of a clinically acceptable, non-invasive glucose meter is likely to lead the way for the development of similar NPT systems for other analytes.

Simple disposable non-instrumental systems have been widely used in NPT for many years. Urine dipsticks have been widely used and similar technology now allows several tests to be performed simultaneously. These forms of assays have been adapted for general and immunoassay chemistries to a range of formats, such as dipsticks and platforms, and can use a range of specimens including urine, whole blood serum/plasma, swab extracts, faeces and saliva [3]. The systems can he designed to incorporate integral procedural controls, which indicate that the operator has performed the test appropriately, and that the reagents are active.

Non-radioactive labels, monoclonal antibodies, and advances in reagent support membranes and reagent deposition have enabled the development of rapid and simple immunoassays where the presence of analyte can be indicated by a coloured response on the device. Alternatively, the intensity of the coloured change can be proportional to concentration, or the response used to produce positive or negative symbols to indicate the presence or absence of the analyte. Such systems have proved to be sensitive and rapid, and have been applied in diverse areas including assays of pregnancy hormone, luteinising hormone, drugs of abuse, occult blood, microalbuminuria, and in numerous microbiological assays including antigen and antibody markers of infectious diseases.

In conclusion, new technology is allowing opportunities to increase for NPT. Future developments will extend the type of systems available, the substances that can be rapidly detemined in smaller quantities of body fluids, and the introduction of minimally invasive systems.

References

1. Hobbs FDR, Delaney BC, et al. A review of near patient testing in primary care. Health Technology Assessment 1997;1(5): 1–229.

2. Borriello SP. Near patient microbiological tests. British Medical Journal 1999: 319;298–301.

3. Price CP, Thorpe GHG, et al. Disposable integrated immunoassay devices. In Principles and Practice of Immunoassay 1997:581-603. eds. Price CP and Newman DJ. Stockton Press NY USA.

Papers from Biotecnología Habana`99 Congress.
November 28-December 3, 1999.