As explained here and here, I temporarily combine the announcements of published papers in one blog to save some time. This is part III, where I focus on ordinal outcomes. Of all recent papers, these are the most exciting to me, as they really are bringing something new to the field of thrombosis and COVID-19 research.
Measuring functional limitations after venous thromboembolism: Optimization of the Post-VTE Functional Status (PVFS) Scale. I have written about our call to action, and this is the follow-up paper, with research primarily done in the LUMC. With input from patients as well as 50+ experts through a Delphi process, we were able to optimize our initial scale.
Confounding adjustment performance of ordinal analysis methods in stroke studies. In this simulation study, we show that ordinal data from observational can also be analyzed with a non-parametric approach. Benefits: it allows us to analyze without the need of the proportional odds assumption and still get an easy to understand point estimate of the effect.
The Post-COVID-19 Functional Status (PCFS) Scale: a tool to measure functional status over time after COVID-19. In this letter to the European Respiratory, colleagues from Leiden, Maastricht, Zurich, Mainz, Hasselt, Winterthur, and of course Berlin, we propose to use a scale that is basically the same as the PVFS to monitor and study the long term consequence of COVID-19.
You were just diagnosed with a debilitating disease. You try to make sense of what the next steps are going to be. You ask your doctor, what do I need to do in order to get back to fully functioning adult as good as humanly possible. The doctor starts to tell what to tell you in order to reduce the risk of future events.
That sounds logical at first sight, but in reality, it is not. The question and the answer are disconnected on various levels: what is good for lowering your risk is not necessarily the same thing as the thing that will bring functionality back into your live. Also, they are about different time scales: getting back to a normal life is about weeks, perhaps months, and trying to keep recurrence risk as low as possible is a long term game – lifelong in fact.
A lot of research in various fields have bungled these two things up. The effects of acute treatment are evaluated in studies with 3-5 years of follow up. Or reducing recurrence risk is studied in large cohorts with only 6-12 months of follow up. I am not arguing that this is always a bad idea, but i do think that a better distinction between these concepts could help some fields make some progress.
We do that in stroke. Since a while now we have adopted the so called modified Rankin scale as the primary outcome in acute stroke trials. It is a 7 category ordinal scale often measured at 90 days after the stroke that actually tells us whether the patients completely recovered (mRS 0) or actually dies (mRS 6) and anything in between. This made so much sense for stroke that I started to wonder whether this would also make sense for other diseases.
I think it does. In a recent paper published a couple of months ago in the RPTH by JLR and me, we call upon the greater thrombosis community to consider to look beyond a binary outcome. I stand by this idea, and for that reason I brought it up again at the Maastricht Consensus Conference on Thrombosis. During that conference another speaker, EK, said that the field needed a new way to capture functionality after VTE. You guessed it, we got together over coffee, shared ideas, recruited SB as a third critical thinker, and we came up with this: a call to action to improve measuring functional limitations after venous thromboembolism.
This is not just a call from us to others to get some action, this is a start of some new upcoming research activity together with EK, SB and myself. First we need the input from other experts on the scale itself. Second, we need to standardize the way we actually score patients, then test this and get the patients perspective on the logistics and questions behind the scale. third we need to know the reliability of scale and how the logistics work in a true RCT setting. Only when we complete all these steps, we will be certain whether looking the binary outcome indeed brings more actionable information when you have talk to your doctor and you ask yourself “how do i increase my chances of getting back to a fully functioning adult as good as humanly possible”.
I wrote about this in an earlier topic: JLR and I published a paper in which we explain that a single relative risk, irrespective of its form, is jus5t not enough. Some crucial elements go missing in this dimensionless ratio. The RR could allow us to forget about the size of the denominator, the clinical context, the crude binary nature of the outcome.
So we have provided some methods and ways of thinking to go beyond the RR in an tutorial published in RPTH (now in early view).
The content and message are nothing new for those trained in clinical research (one would hope). Even for those without a formal training most concepts will have heard the concepts discussed in a talk or poster . But with all these concepts in one place, with an explanation why they provide a tad more insight than the RR alone, we hope that we will trigger young (and older) researchers to think whether one of these measures would be useful. Not for them, but for the readers of their papers.
The paper is open access CC BY-NC-ND 4.0
, and can be downloaded from the website of RPTH
, or from my mendeley profile.