Data Literacy

Fancy getting a private blood test? I did . . .

This post talks about my health in a somewhat vague way because the specifics aren’t important here. I want to preface the whole thing by saying I’m absolutely fine and you don’t need to be worrying about me.

For the past couple of years I’ve been dealing with an underlying health concern. It might be nothing, but it doesn’t feel right to me, and after a particularly bad time in late 2018, I asked for a referral to a consultant. Fifty weeks later, the appointment came through. 

Once I got a date for the appointment, I started collecting data. I used a (research-led design) health app to track my mood, my pain, my triggers, and my symptoms. But I also sent away for private blood tests. 

There are lots of companies now which will run a range of screening tests on your blood, spit, or whatever else you’d like to send off in a biohazard bag through the post. There’s also a lot of debate about whether this is a Good Thing or not. 

To me this is a question of data literacy. 

With many long-running conditions, healthcare providers expect individuals to collect data. I have spoken about keeping a note of Athena’s allergies before:

I recorded this data in a little leather notebook I wrote in every evening. The app I use to record my current symptoms is just a more advanced version of the same thing. Both will help a physician to make decisions about treatment. The rub is that the vet and the consultant have been trained for years to make sense of that data, whereas I, as a non-specialist, might draw the wrong conclusion. What is meaningful information, and what’s just noise?

We all know the danger of googling symptoms, such as that time you had a bit of a sore neck and then you discover you have neck cancer and you should get your affairs in order. Extremes are noticeable and attractive. We propagate stories such as that time an infra-red camera scan detected breast cancer, because they’re interesting – and because they’re unusual. I’ve seen lots of hot patches on people using infra-red cameras, and its never once been a serious underlying condition. Because as a screening tool, its not that useful. 

Screening tests are problematic. We have two measures that are useful when we think about screening: sensitivity and specificity. Let’s imagine we’d come up with a blood test that aimed to diagnose whether you were in fact a bit of a dick at times. A highly sensitive test would read ‘positive’ for everyone who had ever been a bit of a dick. A highly specific test would read negative if you had never been a bit of a dick. The issue is that sensitivity and specificity are not always related. You can have a highly sensitive test that rightly tells all the dicks they’re dicks, but if it has low specificity it will also tell a lot of people who are not dicks that they are, in fact, dicks. And this will upset a lot of nice people. Conversely, a super specific test will never frighten the good people with a wrong dick diagnosis, but it will also tell a lot of dicks that they’re good people. We want both sensitivity and specificity in our tests. 

Alongside the issue of how accurate the test is, there’s the question of ‘do you need to know?’ Here’s a great thread on the risks of DNA testing for cancer here by Rachel Horton. One of the lines that stands out to me is: “The scarier a result, the more likely it is to be a false positive”

The human body is not something that can be easily categorised. Our biology is a spectrum. Not only may a test be wrong, but you might just be tootling along quite happily with any number of potentially scary numbers attached to you. You may have a perfectly benign cyst in your brain. You may just live with low iron levels. In fact, many GPs are incredibly concerned about how these tests can worry people for no reason. 

Just like you’ve got that weird fleck in your eye, or the way your finger bends at an odd angle, there are lots of little oddities in your body that are perfectly fine. The body has such a great ability to just manage with so many things that don’t quite fit the concept of the medically fit person. 

So with all these sensible caveats in mind: why have I paid for the tests? Like I say, this to me is a data literacy issue. There are rightful concerns to these tests, and healthy people should absolutely not spend money on this unless they really enjoy looking at meaningless numbers (hey – that’s why I have a FitBit, no judgement). But they did give me more information. Specifically that there was nothing obviously wrong other than being highly deficient in Vitamin D like all Scottish people. 

As a semi biology-literate person, I did deliberately select the tests that would be likely to be affected by the health concerns I have, and deselected a number of the tests that I did not think were necessary (but that the company were keen on pushing). I also have a reasonable guess at what’s wrong with me from my GP, and that was later agreed by the consultant.

Personalised healthcare is fast becoming a ‘selling point’ for a lot of services. I don’t think we can stem that tide, so we need to think about how we create more data literate people in all sectors, so others can think critically about what’s being offered them. But health is also scary. The health of our loved ones is particularly scary. Can we ever really be objective or analytical when it comes to health? Is that what these companies are preying on?

I don’t have the answers to these questions, but experiencing it myself has given me a new perspective. And I wonder if this is something we need to start teaching simply as a matter of course: how to deal with large amounts of your own personal data. Probably.

Oh – and after I went to the consultant? I was called to the GP for yet more blood tests.

One thought on “Data Literacy

  1. True, dat . I also have questions about quality assurance for many of the aggressively advertised private tests.

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