Probably the best in vitro diagnostic in the world

08 Aug 2017 3min read

Team Discussion

Multiple authors

Recently, my colleague Hannah wrote about the upcoming changes to in vitro diagnostic (IVD) device regulation and its potential impact on the industry. This got me thinking about a category of IVD’s that I worked on years ago that arguably has had an impact like no other – the home pregnancy test.

To my mind the humble home pregnancy test is the best in vitro diagnostic in the world. In terms of accessibility it is unparalleled and it is truly a consumer diagnostic as you can buy it at your local supermarket, where it is packaged in eye catching cartons that display marketing claims to drive purchase.

Look inside the brightly coloured box, and the test stick itself is a piece of industrial design carefully crafted to look sophisticated, medical, reliable, clean, and elegant. Inside the stick are a set of reagents that need nothing more than the addition of urine to start doing their stuff.

the test stick itself is a piece of industrial design carefully crafted to look sophisticated, medical, reliable, clean, and elegant

For the assay itself then immortalized cells, that secrete monoclonal antibodies specific for the pregnancy hormone hCG, are cultured in the cleanest of conditions. The antibodies are harvested and purified, each antibody molecule weighs only 250 zeptograms (10-21g), and for pregnancy tests these molecules are produced by the kilogram. The urine flow runs a lateral flow test strip and the pregnancy hormone (hCG) is captured in a sandwich assay stuck between two antibodies.

If you are pregnant a coloured line appears in the test window, while pristine whiteness persists in the case of a negative. The control line further up the strip confirms the proper running of the test to reassure the anxious user. The market expects >99% accuracy and that is what is delivered.

Then there is the result itself. Most diagnostics will tell you that you have too high a level of this, or too low a level of that. The outcome is that you need to see a doctor, get further treatment, take some medication, drink less, exercise more, and then come back and more tests will be run.

A pregnancy test is different. For most other diagnostic tests everybody wants the same result: proof positive that they’re normal and healthy. With pregnancy tests both positive and negative results can bring disappointment or relief, fear or joy. The answer is immediate and definitive. Within one minute of peeing on the stick you will know the result … and what a result it is. A result with impact, privacy and no expert interpretation required. No other test gives you this and that is the main reason that I think the home pregnancy test is probably the best in vitro diagnostic in the world.

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