A health economist’s guide to the AMS galaxy

Guest blogger Nikki Naylor (bio below) has written this post about a recent review on the cost-effectiveness of antimicrobial stewardship…

I’ll start this blog post off with a promise – I promise not to use any equations or unnecessarily complex terms that just describe logical concepts (something us economists do like to do on occasion). In return, I hope that you will see past the standard and not-to-exhilarating conclusion of “more evidence is needed” and see some of the more useful messages that sit within this recent review that we have published.

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Acronyms for carbapenem-resistant bacteria (again)

I am currently involved in some research that requires a clear distinction between CPE (i.e. Enterobacteriaceae that produce a carbapenemase) and non-carbapenemase-producing CRE. Since ‘non-carbapenemease-producing carbapenem-resistant Enterobacteriaceae’ is a bit of a mouthful, I need to come up with some sort of acronym. I would appreciate your thoughts on the scheme set out below:

You can read more thoughts on acronyms for carbapenem-resistant bacteria in a previous post here.

Antimicrobials, anti-infectives or antibiotics?

antimicrobial terminology

I am currently reading ‘The Drugs Don’t Work’ by Professor Dame Sally Davies, Dr Jonathan Grant and Professor Mike Catchpole (yes, I know I’m several years late to this particular party). I might do a book review for the blog once I’ve finished it – but an interesting question emerged in the early chapters. The author seem to make a point of referring to ‘antimicrobials’ rather than ‘antibiotics’ in the early part of the book, but later on, antibiotics appears as a common term. Which got me to thinking about what is the most appropriate generic term for what most people would term ‘antibiotics’ (what your GP gives you when you’ve got a snuffle, I mean potentially serious bacterial infection)?

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I have thought a lot (probably too much) about the best way to describe the issue of carbapenem resistance in Enterobacteriaceae. I decided ages ago that CRE (a la the CDC) is the way to go as a generic term to describe the problem. But the more I think about it, the more I am coming around to the idea that CPE (a la PHE) is better. And here’s why:

  • The real issue from a clinical and infection control viewpoint is CPE. Enterobacteriaceae that are resistant to carbapenems by means other than an acquired carbapenemase (i.e. CRE that are not carbapenemase producers) are important, but they don’t seem to have the same capacity to spread as carbapenemase producers.
  • It’s a really confusing situation in terms of terminology. From the “end user” staff member on the front line and patient, all that really counts is whether it is a CPE or not. It’s really rather confusing to tell a patient that the have a “CRE that is also a carbapenemase producer” – easier just to say “you have a CPE”. (I accept that you will also need to tell a patient if they have a CRE that is not a carbapenemase producer – but I think this way around is easier.)
  • CPE is already en vogue in the UK (mainly due to the PHE Toolkit) so using any other term risks confusion at the time of patient transfer. (Clearly, this point is reversed if you are working in the US!)

I still think that “CRO/CPO” is not the way to go, given the gulf in epidemiology between the Enterobacteriaceae and the non-fermenters (although, sometimes, begrudgingly, you have to go there). What I mean by this is that you will sometimes detect a carbapenemase gene from a PCR but don’t yet know whether it is from a non-fermenter or Enterobacteriaceae species. In this circumstance, this has to go down as a ‘CPO’.

So, there you have it, a personal U-turn. CRE -> CPE. But I wonder whether CDC and PHE and the international community will ever agree a common term…

The terms 'horizontal' and 'vertical' intervention leave me feeling upside down, confused

horizontal vertical

I am no expert in HIV, but I know that ‘vertical transmission’ means something very specific:

Vertical transmission: the transmission of a disease from mother to child either during pregnancy, childbirth, or by breastfeeding.

Similarly, the definition of ‘horizontal transmission’ is well defined:

Horizontal transmission: the transfer of an infection from person to person.

So, when I read about ‘vertical’ and ‘horizontal’ interventions in a recent New England Journal of Medicine Editorial and the Controversies blog, I began to get a little confused. I have a PhD in epidemiology so don’t consider myself easy to confuse (in this particular domain), but I would have thought that a ‘horizontal intervention’ would be directed towards preventing horizontal spread of an infectious agent and a ‘vertical intervention’ would be directed towards preventing the vertical transmission of an infectious agent. But this is not how these terms are being applied. Instead, a ‘horizontal intervention’ is being used to describe an intervention applied to every patient (such as chlorhexidine bathing or hospital-wide hand hygiene interventions) whereas a ‘vertical intervention’ is being used to describe an intervention designed to reduce colonization or infection due to a specific pathogen (such as active screening and isolation to prevent the spread of MRSA). The use of the term ‘vertical intervention’ seems especially confusing, since it’s a ‘vertical intervention’ to prevent the horizontal transmission of a specific pathogen!

I fail to see how the terms ‘vertical’ or ‘horizontal’ intervention are useful when there are such well-established definitions for horizontal and vertical transmission. I think that ‘universal intervention’ (such as universal screening or decolonization) and ‘targeted intervention’ (such as active screening and isolation to prevent the spread of MRSA) make a lot more sense. These terms are already in common circulation, so I would urge those who favour the use of ‘vertical’ or ‘horizontal’ intervention to reconsider their terminology.