Other Point-of-Care Devices

There are many examples of the use of very small colorimetric devices for POC applications, such as urine dipsticks and test strips for blood sample screening. While not instruments as such, they are based on clever chemistries and reactions and are often single use, throwaway devices. The reagents required for the test are embedded and dried into a strip which is then dipped into the sample, e.g. urine or blood. The colour changes that result are compared to a colour chart, which is usually provided on the side of the container for the test strips. 

One of the earliest such POC tests developed was the home pregnancy test. It is based on a qualitative immunological antibody assay. It relies on the determination of human chorionic gonadotrophin (hCG) levels in urine, which gives rise to a coloured band if positive. The device is very small and completely disposable. A quality control check is built in where the rest of the urine sample continues along the dipstick and interacts with a pH-sensitive indicator to show that the test has been performed correctly. 

It has been reported that more than one-third of people tested for human immuno-dehciency virus (HIV) in the USA do not return to receive their test results h With the availability of rapid POC qualitative tests and immediate diagnosis, more infected patients will be given their results immediately. The OraQuick Advance test from Orasure Technologies can detect the antibodies to HIV from a saliva swab (or fingerstick blood) within 20 minutes. It is 99.8 % accurate for people who are not infected. It was the first POC HIV test to receive FDA approval in the USA for use in clinics and is now awaiting clearance for home testing. 

Kits for home testing of HIV have been available in Europe from MiraTes since 2000. The MiraTes HIV HomeTest uses fingerstick blood and has a sensitivity (percentage of HIV infected people that get a positive test) of more than 99.9 % and a specificity (percentage of people without HIV that get a negative test result) of more than 99.6 %. 

Biochip-based HIV tests have been developed by researchers at the University of Texas and Harvard Medical SchooF. The chip is placed into a toaster-sized analyser that counts the number of CD4+ cells in the drop of blood. Results are available in ten minutes and correlate well with flow cytometry (the gold standard). The device, which is being marketed by LabNow, Inc. weighs less than 2.3 kg, requires no excess reagents and is battery-operated. 

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