How can we use evidence-based medicine for diagnosis and prognosis?
One way is to use clinical prediction rules, which look at a patient’s symptoms, clinical signs, and sometimes diagnostic tests, – and then uses some maths – to try and quantify the probability that a patient has of having a particular disease or condition.
One of the most well-known examples is the Ottawa Ankle Rule, which combines a series of clinical features (being able to walk and tenderness over particular ankle and foot bones) to help clinicians determine if someone with an ankle injury is likely to have a fracture and will therefore need an X-ray.
There are many prediction rules out there for a whole host of conditions, such as for infection, assessing cardiovascular risk, anxiety and depression, to name but a few. And new ones are being developed and published all the time.
But what we wanted to know is whether a bunch of general practitioners (GPs) actually know anything about them, do they use them, and if so, do they find them useful?
To answer this question, we did a survey of 400 GPs across the UK, gave them a list of clinical prediction rules that we thought would be relevant and asked them if they knew of them and/or used them. Just to add more evidence we also did a systematic review of guidelines to have a look if they mentioned or recommended relevant clinical prediction rules.
What we found is that for cardiovascular disease most GPs knew about and used clinical prediction rules, and most guidelines also recommended using them. GPs mostly used them to guide therapy, but also to comply with guidelines.
Depression was another condition where most GPs reported using a clinical prediction rule, mostly to assess severity or, again, to comply with guidelines.
We were surprised to find out that although the Ottawa Ankle Rule to assess ankle injuries was only recommended by a few guidelines, it was nonetheless used by several of the GPs in our survey. On the flip side, although several guidelines recommended using a clinical prediction rule in the diagnosis of breast cancer, almost none of the GPs we asked used one or had even heard of one.
Quite a few GPs told us they preferred using their clinical judgement rather than following a clinical prediction rule, and some even questioned what the evidence was behind these rules (good question!)… Well we haven’t looked at that systematically (yet!….I feel another study coming on…), but we do know that there are some that are well validated with plenty of evidence, but at the moment are not used.
The bottom line is there are many clinical prediction rules out there, but many of them are not known to clinicians and many don’t seem to be useful. For those researchers interested in prediction rules, maybe there is a need to get together more and find out which clinical prediction rules would be most beneficial to clinicians and patients…and make sure we produce the necessary evidence to help implement them. So what do you think? Do you know of any? Do you use them? Do you find them useful? Answers on a postcard…or better yet in the comment box at the bottom of this page.