One size fits all
The YEARS study was a simplified way to work up patients for possible PE. Here was the method used in picture form.
In words: “YEARS clinical decision rule, consisting of three items (clinical signs of deep vein thrombosis, haemoptysis, and whether pulmonary embolism is the most likely diagnosis), and D-dimer concentrations. In patients without YEARS items and D-dimer less than 1000 ng/mL, or in patients with one or more YEARS items and D-dimer less than 500 ng/mL, pulmonary embolism was considered excluded. All other patients had CTPA.” That’s it – a very simple protocol.
They found 0.6% had a diagnosis of venous thromoboembolism (VTE) at 3 month follow-up, 0.2% had fatal PE. It decreased CT utilization by 14% compared to a standard diagnostic approach.
This simplified protocol worked well, was safe, and provided a one-size-fits-all approach to the workup of VTE. It also reduced CT use by 14%.
If you are happy with the above, stop reading; but if you want to dig a little deeper, this is for you.
I have some concerns with this study. Based on a previous study, with a D-dimer of 750-999, the interval likelihood ratio (ILR) would be 0.48. This means in order to rule out PE, the pretest probability must be very low. Otherwise, the post-test probability would be too high to consider the disease “ruled out”. However, it appeared to have worked in this study. Also, the performance of YEARS depends on the prevalence of VTE in your patient population. A higher prevalence would make YEARS perform worse; a lower prevalence of PE would make YEARS performance even better. In this study population, the prevalence of VTE was 14% (compared to the PERC rule validation study at 6%, for example). Finally, clinicians were not blinded to the D-dimer result when scoring the YEARS variables, one of which included, “PE the most likely diagnosis.” The D-dimer result would obviously skew clinicians’ opinions on this variable, either positively or negatively.
EM Lit of Note is an outstanding blog, which I highly recommend. He had some great thoughts on this paper in a post called – Is the Road to Hell Paved with D-dimers. I think it’s important to note a small issue with his analysis. As you read the post, you’ll note he says the ILR with the higher D-dimer level is 1, which means the diagnostic test has no discriminatory value. Although it’s true a test with a likelihood ratio of 1 is clinically meaningless, the ILR would only be 1 at a D-dimer of 1000-1499. In this study, they used <1000 as the higher cutoff, which has an ILR of 0.48 – not great but also not meaningless. Just bear this in mind when you check out his take on this paper. If you are wondering what ILR (interval likelihood ratio) for D-dimer is, see this EM Topics post – D-dimer Cutoffs Are So 2016.
Simplified diagnostic management of suspected pulmonary embolism (the YEARS study): a prospective, multicentre, cohort study. Lancet. 2017 May 23. pii: S0140-6736(17)30885-1. doi: 10.1016/S0140-6736(17)30885-1. [Epub ahead of print]
Peer reviewed by Thomas Davis.