Risk calculators in clinical practice

I haven’t had my blood pressure checked for a couple of years. I think the last time was for a life insurance medical so I wasn’t given much option. As with all investigations, it’s always worth having in mind what you plan to do with the result, and I’m pretty sure I wouldn’t be in any hurry to take blood pressure medication. We use QRISK in general practice (it is embedded in some of the GP computer systems) and I’ve been playing around with QRISK online. Here’s my QRISK score based on my current risk factors:

 

So, over the next 10 years that’s a risk of 0.8% (1 in 125) of a heart attack or stroke. Most of my risk is related to my age and my gender. Can’t do much about them.

Risk calculators can be a bit weird. You’ve got to be careful how you use them. Let’s assume that in fact I’ve got a slightly elevated BP – perhaps a systolic of 160mmHg, which according to NICE guidelines should be treated at that level. According to QRISK-2 (2011), my risk of a heart attack or stroke over the next 10 years is now 1.3%. That is, in my opinion, remains a fairly low risk (and just a 0.5% increase in absolute terms from having a normal blood pressure).

But, say I have a change of heart, my family insist, and I start on medication. I may then revisit the QRISK calculator a couple of months later. I pop in the same details but also check the box ‘on blood pressure treatment’. Even with a systolic BP of 120mmHg my risk is now 2% over 10 years.

It has gone up! That’s not very encouraging and is a good reminder of the limitations of these tools.

The QRISK information page does suggest the calculator can be used this way:

 Where patients are on antihypertensive treatment, should a pre-treatment blood pressure be used when calculating their risk?

No. QRISK®2 has been designed such that if a patient is taking antihypertensive medication then their current blood pressure on treatment can be used rather than a pre-treatment value.

I don’t have details of the algorithm used in QRISK. Presumably what is happening here is that either there is more harm than benefit from anti-hypertensives, or more likely, the sub-group ‘on blood pressure treatment’ has a lot of confounders which haven’t all been teased out. That means that being on blood pressure treatment is simply a marker of other medical issues that worsen risk when looked at on a population basis.

Risk calculators like this don’t offer some magical glimpse of the future for individuals – they are just playing with statistics and, as QRISK are at pains to point out, are best used with careful real world interpretation.

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UTI and clinical examination – what’s useful?

Medical students and young doctors are encouraged to ensure they have examined the patient at every opportunity. When it comes to rectal examination the surgeons still enjoy trotting out the hoary mantra: put your finger in it or put your foot in it. The excellent Des Spence (prolific blogger as well as esteemed BMJ columnist) has recently covered the issue of rectal examination and pelvic examination – both intimate examinations with an occasionally dubious evidence base.

We all have anecdotal experience where examination has magically highlighted the diagnosis; these tend to be rare but memorable professional experiences. They stand out in glorious technicolour against the grey background of countless negative findings. I’ve always suspected the predictive value for most examinations is dire.

Last week, I was teaching year two medical students about UTIs – I floundered as I encouraged them to pop a hand on the abdomen then realised this isn’t necessarily what I do. My first priority when I see someone (usually female) with a suspected UTI is to get a urine sample from them. As often as not, given most women have a fair idea what’s going on, they’ll proudly produce, often with a dramatic flourish, a jam-jar full of wee. Great. I dip it and we decide how we are going to manage things. Unless some other factor points suggests otherwise I will often miss out any further examination.

The predictive value of examination is often ignored and has little impact on how we teach students. The study in BMC Family Practice, Does clinical examination aid in the diagnosis of urinary tract infections in women? A systematic review and meta-analysis, looked at this type of question. They looked at studies that examined the diagnostic accuracy of at least one symptom or sign related to the urinary tract. In the history they found that dysuria, urgency, nocturia, sexual activity and urgency with dysuria were weak predictors of UTI. Increases in vaginal discharge and suprapubic pain were weak predictors of absence of infection. The only exam findings that clearly favoured a diagnosis of UTI were nitrites or leucocytes on the dipstick.

Students feel they have to do everything and as GPs we have to learn how to cut down and trim the examination to the key elements. That can feel uncomfortable but we need to appreciate the true diagnostic value of what we do.

 

ResearchBlogging.orgMedina-Bombardó, D., & Jover-Palmer, A. (2011). Does clinical examination aid in the diagnosis of urinary tract infections in women? A systematic review and meta-analysis BMC Family Practice, 12 (1) DOI: 10.1186/1471-2296-12-111

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The GP business model – a delicate balance

The GP business model – a delicate balance

Posted on Thursday, May 26, 2011 at northerndoctor.com

I can remember Andrew Lansley making the case at the last RCGP conference that one of the reasons that GPs are ideally placed to be intimately linked to commissioning was because of their independent status within the NHS.

The GP business model is frequently misunderstood. Most GPs are independent contractors who work in their own self-contained partnerships, employing staff and often owning their own premises. GPs have a great deal of independence in how they run their business but many wouldn’t be viable if they weren’t shackled to the NHS. They are not true free-marketeers by any stretch of the imagination. Most GPs have never really been involved in competition and they have enjoyed the privileged position of being in a business that is, collectively, too big to fail. A recent opinion article in Pulse written by Dr Paul Charlson (a Tory) pushes the case for opening up competition and claims that GPs ‘conveniently ignore they are private practices’. He, like many others advocating competition, conveniently ignores the current limitations on the GP business model.

Another article in Pulse suggesting ways GPs might seek to increase their practice list size also highlights the problem. One of the biggest factors in a practice’s income is the size of its list of patients. Therefore, getting more patients may seem like a great idea. Of course, it takes about two seconds to work out that this a zero-sum game. There are no extra people to register and no spares just sitting around waiting to be swept up by a diligent GP. The bottom line is that if one practice takes more patients then it does so entirely at the expense of a neighbouring practice that will lose the income.

The RCGP has been opposed to a relaxation of the rules on practice boundaries. A lot of patients find this irksome – particular commuting types who are rarely in their home areas within working hours. Many GPs will oppose practice boundary abolition out of naked self-interest as maintaining the practice boundary system retains their position of provider privilege. However, the restrictions around practice boundaries have provided a financial safety net for general practice and is one of the factors that helps to ensure a universal service.

The private practice status of the typical GP business is an awkward tension held together by the need to provide that universal service while allowing local flexibility. It isn’t a true blue, devil-take-the-hindmost competitive world and there are good reasons for that. Practices do make a profit but in most cases it is a modest one that pays GPs and their staff a reasonable salary. Most practices can’t make a significant profit above this but the quid pro quo is that they are unlikely to go bust. Don’t be persuaded by the straw man argument that GPs are already private providers and the NHS reforms are a natural development.

We only need to pull a few small threads to unravel the whole fabric of our primary care.

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