Point of care and the art of instrument design

Point of care testing offers a range of benefits for patients, nursing staff and laboratory personnel, but guaranteeing the same quality, sensitivity and reliability as laboratory testing can be difficult to achieve with some POC instruments. Liz Grint discusses the key considerations for effective POC instrument design

Point of care (POC) testing has been a feature of the healthcare environment for many years, with a variety of tests – such as blood gas analysis and glucose measurements – now routinely performed at the bedside. As diagnostic testing technology advances, there is the potential for more and more assays to be performed at the point of care. However, development of robust and reliable POC platforms requires more than simply the technology to miniaturise the assay itself. To be successful, POC instruments must be safe and easy to use for non-laboratory staff, provide accurate and reliable results and stand up to the rigours of a busy hospital environment.

Many POC tests rely on exactly the same assay methods – for example ELISA-type sandwich techniques – as existing laboratory analyses. The difficulty for instrument manufacturers is to replicate the numerous steps involved in these traditional tests in a compact format, without the need for the pipetting and cold storage of numerous assay-specific reagents and consumables. This is generally achieved through a combination of carefully designed, stable chemistries – such as the innovative dry-chemistry technology used in Radiometer’s AQT90 FLEX – and automation of sample handling steps to ensure reproducible performance of the assay and eliminate human errors. The use of proven and familiar methods also provides clinical and laboratory staff with greater confidence in the results of the assay.

Patient and staff safety must be the first consideration when transferring testing from the laboratory to the point of care. Unlike laboratory staff, clinical staff on wards and in clinics are rarely trained in ‘best practice’ laboratory techniques for sample handling and preparation, and so sample preparation should involve as few manual steps as possible to avoid the risk of needle-stick injuries, contamination of samples and exposure of staff and patients to potentially harmful materials. Ideally, sealed patient sample tubes should be loaded onto the instrument for fully automated processing, without the need for reagent addition or manual handling steps.

[caption id="attachment_27276" align="alignright" width="200" caption="Accuracy of results is a key consideration for both clinicians and laboratory staff"][/caption]

As with the introduction of the world’s first blood gas analyser by Radiometer in 1954; the trend towards point of care testing has led to concerns about the quality and integrity of data obtained from POC systems. Although these are valid concerns – potentially vital clinical and therapeutic decisions are often based on the results of these tests – modern POC instruments incorporate a wide range of quality control features to ensure consistent and accurate performance. In addition to factory calibration of analysers and consumables, many POC instruments include mandatory periodic calibration testing and QC sampling, ensuring that appropriate checks of instrument performance are undertaken and allowing truly quantitative and reliable results to be obtained at the point of care.

Another major consideration for laboratory managers is the perceived reduction in compliance associated with moving testing to the point of care, making appropriate monitoring of instrument performance, user training and results interpretation difficult. To overcome this, instruments such as the AQT90 FLEX offer remote monitoring functions, allowing laboratory personnel to oversee instrument usage and operation, and intervene if a problem is identified. Many systems also provide full electronic reporting and audit-ready process documentation, with a number of programmable thresholds and reminders to ensure appropriate standards are maintained. In addition, password-controlled user access provides a straightforward mechanism to ensure that only appropriately trained and qualified staff operate the analyser.

From a clinician’s perspective, one of the most important features of any point of care analyser is the accuracy of the data it provides. As potentially life saving therapeutic decisions can be based on the outcome of a single test, POC instruments must offer sufficient sensitivity to allow rapid decision making, while still offering fast turnaround times and ease-of-use. The clinically relevant sensitivity is likely to vary significantly between analytes, and so it is crucial for instrument manufacturers to fully understand the medical implications and significant thresholds for each analyte to provide easy to interpret results which can be quickly and confidently acted upon.

Introducing laboratory-developed analytical techniques into a point of care setting can be a difficult proposition, requiring a careful balance between data quality and ease-of-use. The AQT90 FLEX is one example of how laboratory technology can be combined with user-oriented design and advanced safety and security features, offering a straightforward solution that meets the needs of the point of care market without compromising on data quality.

The author Liz Grint is a product specialist at Radiometer.