iPlayer Radio What's New?
Listen
On Now : Afternoon Drama
The Surprising Effect of Miss Scarlett Rosebud
Image for Over-diagnosis: Chronic Kidney Disease

Listen now 28 mins

Listen in pop-out player

Over-diagnosis: Chronic Kidney Disease

Duration:
28 minutes
First broadcast:
Tuesday 14 August 2012

Dr Mark Porter finds out that some medical conditions are over-diagnosed and therefore over-treated, because of the results of certain tests.

  • Inside Health - Programme Transcript

    Downloaded from www.bbc.co.uk/radio4
    THE ATTACHED TRANSCRIPT WAS TYPED FROM A RECORDING AND NOT COPIED FROM AN ORIGINAL SCRIPT. BECAUSE OF THE RISK OF MISHEARING AND THE DIFFICULTY IN SOME CASES OF IDENTIFYING INDIVIDUAL SPEAKERS, THE BBC CANNOT VOUCH FOR ITS COMPLETE ACCURACY.


    INSIDE HEALTH

    TX DATE: 14.08.12 2100-2130

    PRESENTER: MARK PORTER

    PRODUCER: ERIKA WRIGHT


    Porter
    Today's programme is the first of two special editions of Inside Health looking at over-diagnosis, and growing concerns that doctors sometimes try too hard. Not an accusation often thrown at the NHS, but last week's announcement that we should be doing more to find the million or so people in England with undiagnosed kidney disease, has prompted accusations that we risk turning healthy people into patients and on the basis of a test of questionable accuracy.

    Winearls
    None of us would be very pleased if the police said well we've stopped you speeding, we think you were doing somewhere 25 and 40 miles per hour and we're going to fine you because you might have been doing 40, I just easily might have been doing 25 - tough mate, the test came out at 38 so here are your points.

    Porter
    And kidney disease is just one of a range of conditions where doctors are sometimes accused of being overzealous. Ray Moynihan is a senior research fellow at Bond University in Australia.

    Moynihan
    The problem that researchers are increasingly identifying is this problem called over-diagnosis and essentially this means that people who don't really need them are getting labels and getting diagnoses. It can lead to people getting unnecessary tests and treatments and it can waste an awful lot of precious resources. And across quite a number of conditions, quite common conditions, there is growing evidence, some of it tentative, some of it very strong and robust evidence, that too often medicine is harming the healthy, perhaps for the best of intentions. One of the biggest problems of course is this focus on early detection and we've developed something of a religion around early detection - the medical literature, public health campaigns, the media is constantly proclaiming the benefits of early detection. And it makes sense, it's intuitive - get something early and nip it in the bud and prevent it. The problem is - and we're starting to see this across many conditions - that if you intervene earlier and earlier you're going to start labelling and treating people who would actually be never harmed by those conditions that you're giving them, you're telling them they have. And so we're starting to see that early intervention, early detection, is a double edged sword.

    Anon patient
    I believe that because the tests had been newly introduced nobody actually really understood the sort of results that they were likely to get and they didn't know how to interpret them and that my results were potentially within the range that was acceptable and normal. So this has been an exercise in medical intervention that gave me a certain level of concern because the people involved were being extremely over-cautious.

    Porter
    One of the burgeoning ranks of the worried well. Inside Health's Margaret McCartney is here and I am betting that stories like that woman's, Margaret, who has asked to remain anonymous, are increasingly common in GPs' surgeries like yours?

    McCartney
    Yes and it's immensely troubling. I mean when I went into medicine my great idea was that I was going to be a doctor that treated people who were sick and yet what it's become is a job where I'm treating well people who have risk factors or possible or potential risk factors for disease and we're trying to modify these. And I think the problem is that that means that we're treating a huge amount of people who actually were never going to develop the diseases that we're trying to prevent.

    Porter
    But the public perception always is that the earlier you catch something the more you try and diagnose something the better surely?

    McCartney
    Yeah and it's so intuitive, your logic is screaming at you to say yes that must work but the truth is that when we look at the evidence for it the way it plays out just doesn't run to what our logic seems to suggest. And time and time again we find that when we try and intervene early we end up doing more harm than actually good.

    Porter
    And that intervention is often based on - it's not based on a patient's story, it's based on other criteria.

    McCartney
    Well that's absolutely right, normally when we treat a patient we have this big thing called history and examination, which means you talk to the person in front of you, you find out what's wrong with them and you try and make a diagnosis based on that and yet we're being encouraged and pushed towards making diagnoses based on simple blood tests that are quite devoid from the patient and what they're experiencing.

    Porter
    And what sort of areas are we talking about then?

    McCartney
    Oh I mean there's so many Mark, I mean sometimes I wonder when we don't - what isn't treated as a risk factor now. So things like cholesterol, things like blood pressure, things like our weight - when people get weighed to see whether they're overweight or underweight in a practice - these would be very much the standard things that it's very difficult to avoid. And of course then there's the blood tests as well and in particular it's going to be kidney function, really on the basis of biochemical blood tests not on the basis of the patient in front of us.

    Porter
    And it's all about numbers and it's numbers rather than symptoms that seem to be taking over in so many interactions between doctor and patient. Jeremy Greene is Assistant Professor in the Department of the History of Science at Harvard University and author of Prescribing by Numbers.

    Greene
    Over the past 50 years we've seen a dramatic change, moving from managing disease as defined by symptoms, things patients feel - a headache, a pain in their belly - towards diagnosis that takes place by pure number alone - what is your blood pressure, what's your cholesterol number, what's your good cholesterol, what's your bad cholesterol - that the numbers themselves created an ethical problem that patients and physicians could not simply shy away from.

    Moynihan
    I think it's directly relevant to the person in the street and I think that a lot of your listeners will already have a fairly healthy scepticism towards the treatments that they're being offered. But what I think the evidence is now suggesting is that they need to develop a more healthy scepticism towards the labels that they're being offered, the diagnoses that they're being offered because increasingly I think those diagnoses, those labels, those conditions themselves are controversial.

    Porter
    Can you give us some examples of some therapeutic areas where you think this is happening?

    Moynihan
    Well let's take chronic kidney disease. There is a very, very fierce debate going on behind the scenes about whether or not the definitions of chronic kidney disease have been broadened far too widely and that many healthy people are being wrongly labelled. And so there is a fascinating debate going on between kidney specialists around the world about whether there is over-diagnosis happening in the area of chronic kidney disease.

    Today programme clip
    Naughtie
    It's 7 o'clock on Monday 6th August. The headlines: An NHS report has called for urgent action to detect and treat chronic kidney disease. And the Jamaican sprinter...

    Porter
    According to NHS Kidney Care last week there are a million people in England with undiagnosed Chronic Kidney Disease or CKD. Scary, particularly if you might you be one of them? And some doctors' ears pricked up too. Chris Winearls is Consultant Nephrologist in the Oxford Kidney Unit at the Churchill Hospital.

    Winearls
    I woke up on Monday morning to hear a news item on Radio 4 describing an epidemic of chronic kidney disease and that a million people were not being properly looked after and I was astonished because that's not the way I see it. And the impression is created that they're in the same basket as this group of people with real kidney diseases, inherited kidney diseases, inflammatory diseases who are our business.

    Porter
    Because we've actually got a spectrum here from normality, is what you're saying, right down to people who've got severe kidney problems that will need dialysis and/or transplant. But that's not necessarily a gradient, once you're on that spectrum doesn't mean you're going to slide down inexorably into kidney failure but that's what a lot of people think.

    Winearls
    And that, I'm afraid, is what the public relations has kind of tried to portray is that if you've got the slightest thing wrong with your kidney you're at risk of finishing up on dialysis and that's a pretty terrifying thought. The problem is that there are quite a large number of people who have a slight problem with their kidney function, they're mostly elderly and it's mostly in the context of other conditions like diabetes, so it's kind of known about already. But someone's put a label on - they've got Chronic Kidney Disease - as if they've got something new and special and individual which separates them from the rest of the population which is going to be lethal and that they're at risk of developing end stage renal failure. In fact virtually none of them will, only about 1% might progress towards dialysis, which is the thing we all want to avoid. So I think it's lumping all those patients, some with a little degree of kidney dysfunction along with the people who've got a serious problem and I think that's what's led to the misunderstanding.

    Porter
    The National Clinical Director for Kidney Care at the Department of Health is Dr Donal O'Donaghue. How sure is he that the million figure is accurate?

    O'Donaghue
    Er, reasonably sure but it's in the ballpark of a million people that haven't yet been identified as having kidney disease within England and it's based on the epidemiological data from Health Survey England and the figures are pretty similar across the Western world, so we have data from America and Canada and Australia showing very similar figures to the UK. We believe that around 6-7% of the adult population have reduced kidney function, which is called Chronic Kidney Disease.

    Porter
    What are those million people made up of - how many of them have significant kidney disease?

    O'Donaghue
    I think the majority of them have milder kidney disease, we still have some people with quite advanced kidney disease who are unknown to the system or unrecognised by the system but that is less now that kidney disease has been demystified. So the majority of them would be perhaps the lowest level that we would be expecting to be picked up. And their benefits probably derived over years and decades rather than the more severe disease where it's really important that they're picked up very rapidly.

    Porter
    So the majority of those - of those million that have been identified in the press are actually going to be at the milder end of the spectrum we would hope?

    O'Donaghue
    I would hope and expect that to be correct. You can think about early kidney disease more of a risk factor than a disease, it's asymptomatic, people don't know they've got it but one can track the level of kidney function by looking at the GFR graph. Very few people with reduced kidney function will progress to have kidney failure.

    Porter
    And Kidney Care has commissioned a national clinical audit to ascertain the likely severity of the million or so people out there with undiagnosed CKD in the community.

    Margaret McCartney, can you explain how CKD is diagnosed?

    McCartney
    Sure. Well we used to measure kidney function just with a blood test to check that your kidneys were able to filter out all the products of protein breakdown - urea and creatinine - that you didn't need any more and you would normally pee out and if you've got kidney failure or your kidneys aren't working properly you would get a build-up of these products in your blood and you could see that when you measure it. In 2006 we moved from just checking this normal kidney function test to a new test called eGFR, which stands for estimated Glomerular Filtration Rate, another test of how well the kidneys are working. And this was reported in five categories basically. So category one and two, we didn't both about, they were quite mild. Category four and five, that's more severe kidney problems, these people are usually under the care of a kidney specialist but CKD three, were this big category of new patients who were being told they had a kidney problem and who really were being left under the care of their GP.

    Porter
    And these are often otherwise healthy people. And in terms of the actual blood test result, we get a number come back...

    McCartney
    Yeah.

    Porter
    ... where's the division between the various groups?

    McCartney
    So CKD 3 would be patients who had an estimated Glomerular Filtration Rate, this eGFR, of between 30 and 59.

    Porter
    And where a hundred would be regarded as being completely normal. I always think of it as sort of percentage kidney function, it's very crude but that's one way of looking at it.

    McCartney
    Sure, sure.

    Porter
    And you don't actually have to order this test?

    McCartney
    No and this is one of the huge problems. So basically I went to work one day and realised that I had this new result that was coming back on patients' blood results. I thought I was just asking for the basic urea and creatinine but what I got back was a CKD category. So this was a risk factor that was being given back to me for patients that I'd really only expected a urea and creatinine. So this was a completely new diagnosis really.

    Porter
    And to put this into context - that urea and creatinine is one of the basic blood tests we do along with things like full blood counts, so it's happening to almost everybody who's having a blood test?

    McCartney
    Yeah absolutely, so anyone that's on a blood pressure treatment, for example, the urea and creatinine would be something I would measure annually but this CKD was something new, it had not been done before and a new diagnosis really for patients that wouldn't have had it measured previously.

    Porter
    Which is exactly what happened to our patient who had a blood test for something completely different.

    Anon patient
    When I called back for the results I was told that an additional test had been done to check kidney function, that this had given rise to some concerns and there was nothing to worry about but they would like to investigate to see whether there was in fact a problem with my kidney function. This all took six months. I was extremely annoyed because I hadn't given informed consent to the test being taken place and it hadn't been properly explained to me why it was being done or what the actual expected outcome or the problems that they had diagnosed actually were and I was left in doubt for six months, only to be told that in fact there was no problem at all. They now knew my kidney function level and this was a benchmark against which they could measure the deterioration of my future life and if it deteriorates at the rate that they predict without treatment I would need kidney dialysis aged 90. I thought this was completely ridiculous because I believe that by that time I would probably have developed other medical conditions which may actually have prevented me from reaching 90.

    Winearls
    I trust the test for where it was designed. It was actually originally worked out in people who did have genuine kidney disease and it's quite accurate in people who've got poor kidney function. Unfortunately it was extrapolated to the population as a whole. My concern was that the test didn't really apply to the general population with relatively normal kidney function. And the other thing we know is that as you get older the amount of kidney function you have reduces, so the amount of kidney function a 60 year old man has is less than he had when he was 20 but it's also quite variable. And the normal ranges, well really the normal ranges for young people, not for older people, so a lot of older people suddenly found that they weren't as young as they ought to be and the kidney function was described as being abnormal but they probably didn't have anything wrong with their kidneys at all, in fact when you tested them you couldn't find anything but the number came up as a low level of kidney function. So it was concluded that they had chronic kidney disease.

    Porter
    So the troublesome group in terms of using this test over the blanket approach in the community is this group of CKD 3, the people who come in just under 60, who might be outwardly otherwise healthy were then suddenly then out of the blue told that they'd got a kidney problem.

    Winearls
    And that's 6% of the population, that's where - that's where the problem arose. The people in stage four were .14% of the population, those are the ones that nephrologists are very anxious to see. The 6% at this stage 3...

    Porter
    Millions of people.

    Winearls
    ... millions of people.

    Porter
    Consultant Nephrologist Chris Winearls. So what does Kidney Tsar Donal O'Donaghue think of the test?

    O'Donaghue
    It's certainly not a perfect test and it's based on measuring the creatinine in the bloodstream. And the creatinine is really a function of the muscle bulk of the individual and the level of kidney function. So there's a lot of factors that will alter muscle bulk - so body building or a mountain biker at one extreme to a very thin and emaciated person at the other extreme. So that's, if you like, the first problem. I think the second problem is that the assay itself for the creatinine is not a perfect assay and we don't have as good a measure of kidney function as we would like in the ideal world. And then the third problem with the way we measure kidney function lies in the estimated of estimated GFR or estimated kidney function.

    Porter
    There's quite a few variables there, I mean the reason why I mention - you must have heard this, doctors amongst themselves sometimes talk about the E standing for erratic because the results can vary so much from person to person from week to week, depending on what they were doing just before they had the test and it seems, if we're going to classify people as having some form of disease, in this case chronic kidney disease, that we should have a test that's accurate?

    O'Donaghue
    I think that before we classify somebody as having Chronic Kidney Disease we need to be asking the question why have we done this test and you're quite right it often comes without the doctor having thought about it or certainly the patient raising it as an issue. But if it looks like there might be kidney disease then I think the doctor need to put their thinking hat on, see if there's protein in the water and look at the patient in front of them.

    Porter
    One of the concerns I have as a GP is that we often don't order this test, as we've discussed already the test result comes back as part of other routine tests that we've done, the patient then gets told that they've got stage 3 Chronic Kidney Disease, they're obviously alarmed by that and as their clinicians in an otherwise perfectly healthy person I'm not sure of the significance of it either. They feel that they've been turned from a normal person into a patient - is there a worry that we're over diagnosing normal people here to pick up the few who do need our help?

    O'Donaghue
    I think it's a legitimate worry. I think that what we do know for the population is that as being a slightly reduced GFR stage 3, 3a that that as a population those people will have increased vascular risk. I don't think the word chronic is particularly helpful, it means something different to our public than it does to you and I Mark and the person doesn't have a disease, so the word disease is also difficult.

    Winearls
    I mean you could imagine the general practitioner getting a piece of paper saying your patient has got CKD stage 3, they've got seven minutes, I think, for their consultation, many of them act as a triage point for patients but if someone's told they've got CKD stage 3 they want to see a kidney specialist. I know this because if doctors get told they've got CKD stage 3 they don't say to their GP I'll let you handle it, they're on my doorstep within 48 hours.

    Porter
    And has that happened to you?

    Winearls
    Indeed, so I have worried doctors coming to see me and I have to explain this to them.

    Porter
    Had you been in charge of the introduction of this test are there things that you would have done differently, are there other ways that you could have tweaked this to make it work a little bit better in your opinion?

    Winearls
    Yes I would never have used the word Chronic Kidney Disease, I would have used the word kidney dysfunction, just on the basis of the GFR. I would not therefore have said that you could make a diagnosis of kidney disease on a single blood test. I would have written to the general practitioner saying your patient has lower kidney function please consider the following possibilities. What I wouldn't do is provide them with an automatic diagnosis - that's lazy medicine, you don't make a diagnosis on the basis of a single blood test. That's the first thing I'd have done. The second thing I would have done is used the very beautiful age nomagrams which show the change in kidney function with age and I would have then taken an 80 year old person who had say kidney function of 60 and I'd have said well for your age you're actually in the middle, you're average for your age but you're not the same as your grandson, so your grandson's got twice as much kidney function as you but he's your grandson. So I would have said interpret this test on the basis of the patient's age.

    Porter
    But surely that's such a simple thing to do - the age adjustment - that we could make that part of the automatic process could we not?

    Winearls
    Well, I lost that argument because the view was that if you're a hundred and you've got 50% kidney function you're going to be vulnerable because you've only got 50% kidney function and I didn't really buy into that argument, I think anyone who's a hundred is vulnerable but I did use that argument nationally.

    Porter
    But last week's NHS Kidney Care report made it clear that kidney failure is not the only worrying outcome for people with Chronic Kidney Disease - more of a worry for those at the milder end of the spectrum is that CKD is now being thought of as a major risk factor for an early heart attack or stroke. Both of which are much more common than kidney failure. Donal O'Donaghue.

    O'Donaghue
    Well kidney disease is a silent killer and in many ways I think we should think of it as a risk factor, so it's a vascular risk factor and it increases one's risk of heart attack or stroke or other vascular event. It's also often caused by vascular disease because the kidney filters, the workhorse, if you like, of the kidney, are glorified blood vessels and they get damaged by the same things that damage other blood vessels, raised blood pressure, raised cholesterol, smoking, diabetes. And the upside of things is that the kidney's protected by the same things that protect us from vascular disease - exercise, diet, control of blood pressure and so on and so forth.

    Porter
    So just to be clear you're regarding this decrease in kidney function in much the same way as we might regard other risk factors like a high cholesterol level of raised blood pressure, these are often silent and if left unattended could cause problems for the person later in their life. But that might not be kidney failure?

    O'Donaghue
    Quite right, perfectly right.

    Porter
    But is this link with stroke and heart attack due to reduced kidney function - or is it due to a combination of pre-existing factors that damage the blood vessels in the kidneys as much as they damage the arteries supplying the brain and heart? In other words reduced kidney function is simply a marker of other processes, and not a risk factor in itself. Chris Winearls.

    Winearls
    That is the really tricky unresolved issue. Does having a degree of kidney function add to your risk of having heart disease in the same way as cholesterol and blood pressure does? And we're not absolutely sure. The estimates are that it probably contributes about 20% of the risk, there are some people who think it doesn't add to the risk at all.

    Porter
    Because this is interesting because this is another thing that's been out in the Department of Health release is that if we treated these people more aggressively we could save thousands of lives and thousands of unnecessary strokes and heart attacks. What you're saying is that that's not necessarily widely accepted?

    Winearls
    It's not widely accepted because those patients who've got a slightly low GFR probably already have another reason to be at risk of heart attacks and strokes, they've probably got raised blood pressure, raised cholesterol or they're diabetics. The implication that just a lower GFR puts you at risk of significant heart disease and strokes is a very worrying proposal and I'll tell you why. We're doing in this hospital 50 or 60 living donor transplants a year, these are fit people who we're taking 50% of their kidney function away - okay they get - the other kidney increases its function a bit but many of them drop their GFRs below 60. Now if that alone gives you a risk of heart attacks and strokes, just having a reduced GFR, then we shouldn't be doing kidney - living donor kidney transplants because what we're actually doing is giving them a risk factor, like cholesterol and like blood pressure, we just don't believe it, that that pure reduction in GFR is the cause of cardiovascular risk. We think it may be an accelerator in people with or aggravate in patients who've got some kidney disease or have got diabetes or hypertension, having a low GFR, but we don't believe a pure reduction in GFR is a risk factor.

    Porter
    Have you been able to follow your live donors long enough to monitor their long term health in that way?

    Winearls
    Indeed and there's several studies showing that long term survival of living donors is as good as the general population.

    O'Donaghue
    People should not be thinking this might mean they will progress to dialysis and transplantation but they should be thinking this means I can derive more benefit from stopping smoking, taking more exercise, getting better blood pressure control.

    Porter
    But it's unlikely that we're going to be any more successful in encouraging lifestyle modification in people with Chronic Kidney Disease than we are with any other so essentially these people are going to end up on medication many of them?

    O'Donaghue
    I think that's right yeah and they'll benefit from medication.

    Porter
    Donal O'Donaghue. And for most people that means drugs like ramipril to lower blood pressure, and statins to reduce cholesterol.

    Anon patient
    I was told that taking a very small dose of ramipril would help to slow down the deterioration and so I have obediently taken this regularly everyday with no idea whether in fact it is really necessary or what the outcome would be or the consequences if I stop taking it. I'm also on statins and then I have to take this tablet, so they're all medicating my life.

    Porter
    An all too common dilemma Margaret McCartney I expect you see quite a few patients like that don't you?

    McCartney
    Oh absolutely and I think this is one of the big problems, that we've got very little evidence of what the potential harms are now we've moved to CKD testing, we don't know whether we're actually making an effective intervention, are we usefully picking up people with this risk factor? I don't think we know that at all. And the other problem is what harms do we do? Are we therefore over-medicating people, giving people a lot of side effects and ill effects from taking more tablets than they're going to benefit from and what are the psychological effects of being told that a bit of your body isn't working properly? Sometimes I'm really amazed as a doctor just the kind of things that people get quite distressed or upset about and I think with very good reason. And I think these are the kind of things - these kind of very tangible harms - that we really have to account for properly, it's not good enough just to introduce a new test into the population and say well there you go, we should really be much more careful about this.

    Porter
    And this is a common problem, looking at the details of our practice we've got something like one in 15 of our adults can expect to fall into the CKD 3 group, so we're going to be having this conversation frequently.

    McCartney
    Absolutely and what we don't know are how many of these patients we're usefully making this diagnosis in, who are the patients that we can offer something effective and useful to do on top of that?

    Porter
    Margaret McCartney, thank you very much.

    We will be continuing the over diagnosis theme next week when we look at high blood pressure - a condition that affects one in five adults in the UK. Around two million of whom are now though to have been misdiagnosed and don't actually need the drugs they are taking on a daily basis. But which two million? And cholesterol - should children be tested? Join me next week to find out.

    ENDS

Broadcasts

Free download

  1. Image for Inside Health

    Inside Health

    Demystifying the health issues of the day that confuse us. Inside Health, with Dr Mark Porter, will…

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.