Posted 29 April 2020
Today a shorter piece.
Other commitments have (mostly) taken me away from thoughts of COVID and that is probably no bad thing for mental and emotional clarity. But equally, as I have got myself into such a good rhythm of delivering daily posts, the borderline (maybe not so borderline) obsessiveness in my character forbids me from letting a day pass without at least one COVID related post.
So let me ponder two avenues of thought – Testing and Vitamin C.
TESTING
A lot of information from disparate sources has come my way regarding testing. I would not be doing the inputs justice to do anything other than devote a whole post to them, but let me perhaps pin some highlights here.
Today, there is much coverage that here in the UK, COVID testing has been made available to 1.5 million extra people. This has to be good news. Here are my thoughts:
– This is PCR testing, so it is the swab based test that tells -you if you currently have the infection. In many ways, this is key and will make a difference in front-line roles. If a key worker has symptoms that could be COVID-19, previously they would have automatically to isolate for fear they might have the infection and spread it. This has depleted workforces in key areas causing strain. If these people can now be tested we can know if the infection is truly COVID based and so more accurate decisions can be made on isolation. This should reduce strain on workforces in key services.
– Reliability? This is a big question with PCR testing and something being increasingly studied. False positives and false negatives have been an issue with PCR testing and there is now some interesting data on this. Whilst more testing is far better than no testing, accuracy is an important part of the analysis too.
– Previously we have only carried out PCR tests on patients on admission to hospitals. This is not a truly random sample of the population as they are ill and presumably quite seriously ill to need admission. And if they are ill they are more likely to have a COVID infection. Therefore the chances of the PCR test being positive on these people is high. Now tests are being carried out on people not entering hospitals (hospital admissions are still being tested of course) and so we would expect the proportion of positive tests to decrease as potentially lots of not-so-ill people are now being tested too. This is already evidenced in the data.
– However, because of the latter point, the total number of new cases each day will now rise. We are sampling more people so even if the rate of infection is going down, the absolute number of tests showing new positive cases might begin to increase again. This will not be because infection is increasing it is just that we are looking in more places to find it!
– Testing the general population for signs they have had the infection and recovered – something I previously called antibody testing – is not yet being scaled up in this country. Knowing how many have had the infection is a key ‘known unknown’ in all of this. If 3% of us have been infected or if 30% have been infected is a game-changing difference either way as to how and when we start the journey to normality again.
– Studies are showing that some of the early ‘antibody tests’ may not have the specificity or sensitivity once thought, giving incorrect measures. More accurate ELISA based tests are available but not yet on a scale to allow a big enough random slice of the population to be assessed.
VITAMIN C
My nutritional interests means I am inevitably looking at data with regard nutrients and COVID-19 outcome. You may have seen my piece last week regarding Vitamin D. That was perfect for me as it was a well structure trial conducted on real data and so gives us an early measure of the possible correlation between Vitamin D and COVID-19 outcome.
There is always a debate though (and this is prevalent in all nutrition studies) that if you look at one particular element of diet and how it affects a sub-population, is that nutrient a maker or marker of the better outcome. Is it Vitamin D that gives the better outcomes or is it because other lifestyle factors that improve the outcomes also raise Vitamin D levels? If you remember my diagrams from yesterday’s posts, it is like my reading age and shoe size example where age (in that case) and some other factor (in the Vitamin D case) is omitted from the diagram.
A few hospitals (China, US and Italy) have reported using intravenous Vitamin C to manage outcomes with severely ill COVID-19 patients. We would all love this to improve outcomes because it is simple, available now and cheap. The question is do we have enough evidence to support this as a treatment modality of COVID.
This for me is ongoing research, but so far I fear we do not have the robust evidence yet of a similar objectiveness to the Vitamin D study.
My thoughts
– The clinicians at the hospitals where intravenous Vitamin C has been used report that the intervention made a difference. However, these were not clinical trials in the sense of there being a rigorously designed control group against which to compare the results. As such these are no more than anecdotal studies.
– I have found one meta-study investigating correlation between intravenous Vitamin C and the length of time of mechanical ventilation for patients with severe respiratory distress (conducted a few years ago so not COVID related). This study reported mixed results – some studies showed a reduced time on ventilators with those patients given Vitamin C, but not all studies. This meta-study is now perhaps of less relevance to COVID-19 because the role of ventilators and COVID outcomes is now being questioned.
– I have found papers describing two more rigorous Vitamin C studies that have been established but they are both still being conducted, and neither is due to publish results before September.
– I have found some papers offering possible mechanisms by which Vitamin C could help COVID outcomes. These are great papers but they are ‘models’ (in the same way that we have data models for COVID cases) – abstracts that may work in theory but are as of yet untested.
– I have found other papers with different models that counter the above models!
I am still looking and I am still researching. Watch this space.