Testing Times Update

After my earlier post, in which I looked at the underlying principles behind diagnostic testing, the controversy lingers on. This week, the slightly embattled  Health Secretary, Mr. Matt Hancock, announced the UK would be carrying out 100 000 individual tests per day by the end of the month. However, this was reported in a longer article The Guardian as follows:

Matt Hancock, the health secretary, talked with confidence of achieving 25,000 virus tests a day for those ill in hospital and NHS staff who have symptoms or are in a household with somebody who is sick, so that they can go back to work. These are PCR (polymerase chain reaction) swab tests, sometimes called antigen tests, which need to be processed with specialised kits in a lab.

Yes, the mixing of immunology and molecular genetics once again! But I wanted to just make sure that you understand the current challenges that  face those trying to deliver the necessary materials for the tests, which comprise:

Enzymes (polymerases to amplify the viral RNA and turn it into DNA)

Solvents (phenol, chloroform etc to separate proteins, lipids and nucleic acids)

Salts (buffers and stabilisers)

Fine chemicals (nucleotides and the reagents for synthesising DNA (phosphoramidites and the appropriate solvents etc). 

The majority of these materials are typically imported from the EU, North America and East Asia. There is no doubt that the small labs (the University and Research Institute Labs that Sir Paul Nurse referred to as the equivalent of the Dunkirk little ships flotilla) have the capability and capacity to produce enzymes and to synthesise some of the "primers" needed for PCR, but the core reagents and solvents will require re-purposing some of our larger Chemical Industry Sites and possibly shifting synthesis priorities at some specialist Chemistry/Pharmaceutical manufacturers. I think we may reflect on our Global outsource models for maintaining the integrity of some of our supply chains in the aftermath of Covid-19?

Diagnosing Heart Disease with an ECG

The second point I want to raise is the value of the tests, by which I mean, how will testing on this scale help us beat the virus? The test to establish whether an individual is infected by Covid-19 or any diagnostic test, determines how you manage that person's recovery and also how best you protect those who have been in close contact. In an ideal world, where a "cure" for Covid-19 was available, an individual would be given the medicine, either to take home or as part of a short stay in hospital. This would be the case for many heart diseases, for example. In the absence of a cure for Covid-19, the treatment is largely a matter of support based on the patient's age, general mental and physical state and underlying health conditions. Essentially, the patient is nursed as s/he marshals her/his immune system to fight off the viral infection. 

This is an important issue in medicine, that all of you considering any form of  career in the healthcare sector should think about: the fact is that diagnosis often comes before a cure. Take the case of the breast cancer associated genes, BRCA1 and BRCA2 where certain mutations can increase the risk of contracting breast cancer. Pretty soon after the genes were discovered, diagnostic tests became available and many women were tested. In the months and years after, the tests became increasingly common. However, the knowledge that an individual carrying specific mutations in these genes was at a higher risk of developing early onset breast cancer became very sensitive. In the absence of a cure, the knowledge that you are at higher than normal risk can be liberating for some and devastating for others, from personal family experience. We need to understand that the value of testing for a disease that cannot (yet) be cured, must be fully explained. In the case of viral testing is an aid to developing management strategies for minimising the scale and rate of spread of the outbreak, it is also a means of increasing the accuracy of predictions and forecasts. 

There has a considerable amount of debate around who should be tested. Some argue the healthcare professionals ranging from those on intensive care wards, where patients are experiencing life threatening symptoms, to those who argue patients should come first. Basically, we need to have the capability of working through the population as quickly as we can with the priority individuals identified as being critical for reducing the impact of the pandemic.