Thursday, 1 August 2013

To self-monitor blood glucose or not?

Today's news greets us with a story about "rationing" of diabetes glucose test strips. Diabetes UK, in a survey of about 2,200 people, found that 39% of people with diabetes have had their prescriptions refused or restricted. Meanwhile, politicians are wading in stating that restrictions are unacceptable.

Now, this sounds bad. But when you start applying some skeptical principles to this area, it all becomes slightly less clear. Here are some brief points to consider about self monitoring of blood glucose (SMBG) to put today's news into context:

Test strips are expensive. Spending on test strips in the UK is pretty high, and has been rising year on year since 2008. In 2010/2011, a whopping £158.4 million was spent on testing in England alone. These things are expensive, and a lot of them are being prescribed. Historically, they have been over-prescribed, and this has been a priority area for the NHS to attempt to prescribe more rationally. (NB: rationally does not necessarily mean rationing, it just means using resources more effectively.)

The UK Guidelines are clear that SMBG has an established place in the management of diabetes controlled by insulin, whether this is type one or type two. Its also accepted in the guidelines that it is useful for patients with type 2 diabetes who are at risk of hypoglycaemia. Reports such as this one from the NHS Diabetes Working Group are also clear that rationing should not be undertaken in patients who are deriving benefit from SMBG. 

SMBG doesn't actually do anything to control diabetes. It isn't an intervention, it's a testing tool. The only way it can have a positive impact on diabetes treatment is if the results are used to guide treatment or behavioural choices. So its useful for insulin dosing, for example, as it is variable and needs to be responsive to what you have eaten that day. However, if you take a twice daily dose of metformin 500mg, say, SMBG isn't going to really help anything. I think this point isn't quite as clear as it should be to some patients, carers, and even healthcare professionals. 

It only gives you a result for one pinpoint in time. It doesn't tell you anything at all about more long term control. This limits how useful it is in assessing lifestyle changes, such as exercise and longer term changes in diet.

Studies have found that some patients are not using SMBG to guide treatment changes or choices- so they are essentially testing for no gain at all. If this is the case, then it is clear that the SMBG can be discontinued with no impact on the patient's overall care- in fact its an all-round win situation, as the NHS saves some cash and the patient no longer has to bother doing a painful test.

Its not a no risk option. Apart from the obvious discomfort of testing, there is some (although limited) evidence that some patients can feel more depressed, anxious, and even obsessive if they are using SMBG.

The evidence that SMBG works is very limited, and is confounded by lots of different factors. You can find more detailed information on the evidence base in this Medicines Q&A. The technology of SMBG was welcomed with open arms by patients and healthcare professionals alike, and it was widely accepted before there was robust evidence that it worked to improve outcomes. In these sorts of situations, where people are used to using a technology or drug etc, it becomes quite difficult to start being rational about it, without people feeling that they are having something taken away from them. If you really want to have a good look at the evidence, you can have a look at this Health Technology Asessment by Clar et al. It's only 156 pages long (!) but it is a really good quality summary of the evidence.

The evidence that SMBG is cost effective is even more limited. We simply don't know if it represents good value for money for the NHS. Meanwhile, there are interventions which we do know are cost-effective. So doesn't it make sense to limit spending on the unknown, and to put funds into the interventions that we know work instead?

Its a real shame if these sorts of issues have been ignored in favour of rationing. Rationing test strips for patients who are insulin treated isn't rational prescribing, its just daft. But there is a serious issue of overuse and over dependence on SMBG, which blanket rationing makes more difficult to address. The UK guidance makes a lot of sense given the state of the evidence we have access to at the moment, and I would be very sorry to see it being misused in some patients, whilst others are fruitlessly undertaking a needless task at a potential cost to their quality of life and the NHS.