The problem with nudges is that sometimes they don’t move things very much

Have you ever prescribed azithromycin when you didn't have to? Know what I mean?

Have you ever prescribed azithromycin when you didn’t have to? Know what I mean?

Over-prescribing of antibiotics is a problem because it speeds up the rate at which bacteria develop resistance. In a new study was published in the Lancet yesterday, researchers attempted to use a simple `nudge’ to get doctors in the UK to prescribe less often:

In this randomised, 2 × 2 factorial trial, publicly available databases were used to identify GP practices whose prescribing rate for antibiotics was in the top 20% for their National Health Service (NHS) Local Area Team. Eligible practices were randomly assigned (1:1) into two groups by computer-generated allocation sequence, stratified by NHS Local Area Team. Participants, but not investigators, were blinded to group assignment. On Sept 29, 2014, every GP in the feedback intervention group was sent a letter from England’s Chief Medical Officer and a leaflet on antibiotics for use with patients. The letter stated that the practice was prescribing antibiotics at a higher rate than 80% of practices in its NHS Local Area Team. GPs in the control group received no communication. The sample was re-randomised into two groups, and in December, 2014, GP practices were either sent patient-focused information that promoted reduced use of antibiotics or received no communication. The primary outcome measure was the rate of antibiotic items dispensed per 1000 weighted population, controlling for past prescribing. Analysis was by intention to treat.

This is a fairly standard behavioural intervention – use information (or, less graciously, spam) to nudge people into behaving in a more optimal way. The behavioural insights/economics crowd loves these interventions because they are cheap, so the cost-effectiveness hurdle is easy to overcome. However, that cheapness sometimes overshadows a bigger problem, that frequently these interventions just don’t have very large effects. Here are the results from the Lancet study:

Between Sept 8 and Sept 26, 2014, we recruited and assigned 1581 GP practices to feedback intervention (n=791) or control (n=790) groups. Letters were sent to 3227 GPs in the intervention group. Between October, 2014, and March, 2015, the rate of antibiotic items dispensed per 1000 population was 126·98 (95% CI 125·68–128·27) in the feedback intervention group and 131·25 (130·33–132·16) in the control group, a difference of 4·27 (3·3%; incidence rate ratio [IRR] 0·967 [95% CI 0·957–0·977]; p<0·0001), representing an estimated 73 406 fewer antibiotic items dispensed. In December, 2014, GP practices were re-assigned to patient-focused intervention (n=777) or control (n=804) groups. The patient-focused intervention did not significantly affect the primary outcome measure between December, 2014, and March, 2015 (antibiotic items dispensed per 1000 population: 135·00 [95% CI 133·77–136·22] in the patient-focused intervention group and 133·98 [133·06–134·90] in the control group; IRR for difference between groups 1·01, 95% CI 1·00–1·02; p=0·105).

Let’s focus on the intervention that worked: the peer information treatment. There was a clear decline in antibiotic use for the treatment group, and so the study focuses on the sheer number of prescriptions that were prevented (73,406). However, in terms of relative impact, the study barely changed behaviour. The treatment group’s prescription rate was a mere 3% lower than the control group’s rate. 

So if this is about finding cost effective ways to reduce prescribing, then I’m on board. But clearly these sort of nudges are not going to win the war on antibacterial resistance any time soon.

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