What’s your NNT? St.Emlyn’s

I am going to make some assumptions here, basically that you know what an NNT – the number needed to treat is. If you need a reminder then please, PLEASE, click on the video below and listen to the most excellent explanation from the Jarone Lee’s blog at the NNT.com.


I would not, and could not even hope to, replicate their super work here. It’s a great site and you should check it out – but – that is not my purpose today. Rather I’m feeling a little introspective again (as we often are in Virchester) and I was wondering about how much of a difference I, as an emergency physician, make. I like to think that I make a difference in my clinical practice, and I’m sure you do to. For EPs the financial reward does not really go far in making up for the hours, weekends, conflict, etc. that pervades our practice. Most of us (the best of us I’d say) seem to be motivated by a love of the work and a feeling that we are doing good clinical work. Now if that’s all you need to go back to work with a warm glow inside then that’s great, you can pretty much stop reading now.

You’re a great doctor – go forth and heal the sick

The thing is, I’m still a bit worried and maybe this is just me. The thing is,  it’s difficult to see my contributions in isolation as I am usually helping (hopefully) my patients as part of their therapeutic journey. By this I mean that as patients come to see us we are intimately involved in their clinical progress through the system. We meet them, talk to them, examine them, investigate them, diagnose them, treat them, refer them, send them home…., all manner of things really, and at every point in the chain of events that we are involved with there is the possibility to influence care in a positive, neutral or negative way.

Stop and think for a second

How many cases can you recall that you (and only you) made a life saving difference to a patient?

I did this recently and to be honest I was fairly surprised that the number of cases where my personal intervention made a life or death outcome difference is pretty small. Perhaps diagnosing a ruptured AAA in a 28 year old is up there (and then persuading the surgeons to see the patient NOW and that I was not mental), might be up there, but that was some time ago. Dissapointing? Perhaps, but not really surprising I guess. You see as an intervention it’s quite difficult to tease out the personal contribution that we make to patients. Some days I feel a bit like aspirin in myocardial infarction. Damned important, in fact REALLY important at the beginning of the process, but ultimately part of a chain of events that must be in place for the patient to have overall benefit. Now aspirin in MI has an NNT of about 1 in 42 (thanks NNT.com again) but I can’t imagine that I am anything near that to be honest. Aspirin is amazing stuff so it would be tricky to compete…., but that then begs a different question.

If NNT is a comparison, what does a personal NNT compare to?

Damn, I thought I was on to a nice easy concept, but it just got tricky again. So, when we are calculating NNT’s we are comparing a therapy (in this case the therapy is weirdly ourselves) to something else…., but what? Another consultant? Another EP? A junior EP? A non-EP? An absence of health care? What exactly can we compare ourselves to in any meaningful way that makes a difference to us and the way that we practice? Let’s look elsewhere for a moment. Now, the lovely Mrs C is a Corneal Surgeon and her world is different in many ways. For starters we are arguably both intellectual singularities.

She knows pretty much everything there is to know about pretty much nothing (the cornea)

I know pretty much nothing about everything (the entirety of medicine, education and cycling)

No, apart from that she works in a finite field where outcomes are easy to define, measure, audit and compare. Corneal graft survival, complications, failures are all recorded and compared with pre-existing clinical conditions, graft characteristics, cell counts etc. stuff I don’t really understand to be honest, but clearly this is a million miles away from our speciality with it’s varying pattern of workload. Similarly, our other surgical and medical colleagues are increasingly being subjected to analysis to give comparisons of how they are doing when dealing with particular conditions, but I’m not sure it works in the world of EM -certainly not for the big stuff that gets referred on anyway.

What about in the world of EM? What comparisons might we consider, and indeed what outcomes might define us? To be honest this is a challenge for all emergency physicians as we seek to find the outcome measures that define and explain our contribution to the patient. Entirely patient related outcomes such as death and morbidity would be ideal, but so difficult for us to achieve. Perhaps that is why many EM services are measured against process targets rather than outcome. In the UK this has clearly been led by the 4-hour wait target, but there are others such as the time for senior involvement in serious trauma/illness. Most if not all of these are reasonably sensible but few give me any sense of personal worth, there is no NNT-for-me in keeping the minors stream flowing (though some might choose to measure my worth in such a manner).

We must also consider outcomes. There are the hard outcomes (like death), but what of the other value that we put in around care, empathy, teaching, development, strategy. I have no doubt that there is influence here, but measures? I suspect not.

So, can I compare my worth to colleagues of a similar grade in my department? Well arguably not as we do have natural variability (I prefer the term ‘talents’ to be honest), and I have colleagues who have expertise in areas that I do not have, and I’m sure you do too. Sure, I can compare myself to juniors – but that’s a little unfair, to both of us. Nor can I choose to compare myself easily to colleagues around the world who practice in different environments, with different patients and with different challenges….., I seem to failing to get anywhere here, but I still hanker for a feeling of personal assessment.

So can I have an NNT?

I’ve been pondering this for a while and I think I can. Whilst I cannot find a quantitative number that will define an NNT I do think that there is an excellent comparator for me, you and every other emergency physician out there.

It’s you

It is you. It was you and it will always be you if you want to be a better doctor. To be an excellent physician you must embrace life long learning, and to do that you must accept that you are in a cycle of continuous improvement. Whilst we earlier struggled with outcomes to define our personal NNT, it perhaps does not matter what we choose. It perhaps does not matter whether it is totally clinically focused around a patient outcome, or whether it is a proxy outcoem related to departmental process. What matters to me, and what should matter to you is that you evaluate your personal NNT against where you were. Are you a better emergency physician today than you were last week/month/year?

Ask yourself and give yourself a number. Mine is 42 which is co-incidentally my age (if you want to know why click here).

What’s yours?


Simon Carley

There’s a four hour wait in Minors (2012)
Virchester ED 2004

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Cite this article as: Simon Carley, "What’s your NNT? St.Emlyn’s," in St.Emlyn's, October 10, 2012, https://www.stemlynsblog.org/whats-your-nnt-st-emlyns/.

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