Angry Doctor

Saturday, December 03, 2005

"Quantity Has a Quality All Its Own"

This post from my mentor complaining about the assembly-line workload doctors face got me thinking about a term I learnt from one of those Evidence-based Medicine workshops: Numbers Needed to Treat (NNT).

I failed biostatistics back in medical school, but I believe NNT means the number of patients you need to treat before one of them benefits from the treatment. Applying this to say stroke prevention, it means that a treatment with NNT of 10 means that for every 10 patients you treat, you would have prevented one stroke (which would have occurred if they were not given the treatment).

A more thorough explanation can be found at
this site.

Let's say we take the figure from
this article:

"Two studies of antihypertensive treatment in hypertensive people over 60 years have NNTs of about 40 to prevent one stroke over 4 years compared with placebo. This means that 40 people have to be treated for four years to prevent a stroke in one of them, who would have had a stroke if they had been given a placebo."

So say aliendoc sees 8 patients an hour, for 44 hours a week, and she works 46 week (14 gazetted holidays, 3 weeks leave, one week MC...) a year.

That makes 16,192 consultations.

Let's say half of those are acute cases like cough-and-cold, and that the rest are repeat visits for chronic illnesses like diabetes and hypertension, on 3-monthly visits.

That makes 2024 unique chronic patients.

Given that the prevalance of hypertension in Singapore is about 25%, and given a NNT of 40, that makes 12 strokes prevented.

That's one person saved from a stroke each month.

The numbers may not be exact, but I suspect the order of magnitude should be correct. And we haven't even counted the other complications like heart attacks, or the other chronic diseases like diabetes and high cholesterol.

So how many strokes have you prevented today?

17 Comments:

  • Walio,

    Now medicine reduced to cold statistics.

    I think doctors should concentrate on healing and leave the mathematics and statistics to statisticians. No wonder that are no earth shaking medical breakthroughs in the last 2 decades. Good thing you failed biostatistics. Not only angry but smart. All of them are busy totalling up the numbers of hits, misses and kills. ;0 when they should be conducting cutting edge research into diseases like cancer, aids, new viral strains plagueing mankind this century.

    By Blogger uglybaldie, At December 03, 2005 9:09 am  

  • Statistics is the backbone to our profession. Without it, we are reduced to quacks who prescribe unproven treatment and who just aim to please patients rather than to do them some good.

    Life, as I have said on several occasions, is a gamble. We are just here to advise peope on the odds. Naturally, that means we must know what the odds are to begin with.

    By Blogger angry doc, At December 03, 2005 9:33 am  

  • Aiyah what statistics and do good?

    Medicine is now about customer satisfaction.

    Our duty is to make the customer satisfied and happy when they walk out of the clinic.

    Give them a whole new clinic-consult-dispensary experience.

    They should be going "That was out of this world. I'd definitely be back again!"

    By Anonymous Dr Oz bloke, At December 03, 2005 9:45 am  

  • Dr. OZ,

    Way to go, You'll go far in OZ my boy.

    Welcome to the club.

    I previously sold wealth without any effort.

    By Blogger uglybaldie, At December 03, 2005 10:12 am  

  • Talking about odds & gambling, here's a trick on explaining risks of complications of surgical procedures or side effects of drugs to blur patients: Use the example of striking lottery or 4D - except in the case of medicine, you obviously hope that you don't "strike"! The average patient will probably not understand if you tell them that the chance of him/her developing some complication is x out of a 100; but if you say that it is the same chance as striking consolation prize in 4D, a light bulb will go on in their heads!

    Worked for me!

    By Blogger aliendoc, At December 03, 2005 11:23 am  

  • To Aliendoc,

    One out of 100 is NOT the same as striking 4D in a consolation prize.
    It is probably more like one out of 1000 or more.

    Saying this to your average neighbourhood ignorant bumpkin is fine but do that to a knowledgeable person and there is plenty of smart alecs around these days, and you may find yourself in some shit when the he does strike the prize!

    :-))

    By Blogger uglybaldie, At December 03, 2005 12:18 pm  

  • Moral of the story:

    Don't see smart alecky actually can be smart but want to be infantile and pretend to be stupid type of people when with doctor but later something go wrong turn around and bite you real bad in the butt.

    We find them quite a lot here though.

    By Anonymous Dr Oz bloke, At December 03, 2005 12:57 pm  

  • Hey Doc,

    Get something straight man.

    It's not the hypocritical patients you should worry about. Just worry about what you say, do or don't do.

    You want to practice safe medicine?

    I suggest some remote village in Thailand, Cambodia or Vietnam would be ideal. There they don't have the means nor the access to SMC, SMA, lawyers and a nanny gahmen. And of course not forgetting IT.

    By Blogger uglybaldie, At December 03, 2005 1:08 pm  

  • To Dr. Angry,

    Walio, now I know medicine is like taking a trip to Genting. Well, very soon, we don't have to go there, we can go to our very own IR.

    But yeAH, i AGREE that everything in life is a gamble. Which brings me to comment that if you don't die of Aids or Cancer, you'll probably succumb to the thousands of prevalent diseases of mankind not to mention the emerging and stealthy ones which our medicos have not yet discovered or identified because they are so busy playing the numbers game. Well, that's western medicine for you. I don't trust western medicine totally. I believe the Chinese with their 5000 years of TCM skills and healing prowess is a major contributor to one's health, at least where I am concerned. Having said that, Western medicine is very good at cutting, stitching, clearing pipes and engine overhaul though.

    By Blogger uglybaldie, At December 03, 2005 1:25 pm  

  • To uglybaldie:

    Hence I wrote: "x out of 100" -you can insert the appropriate number to replace the variable x, depending on what you are talking about.

    :)

    By Blogger aliendoc, At December 03, 2005 1:39 pm  

  • huh?

    x out of 100 same as

    x out of 1000+?

    Walio, my maths teacher must have been teaching me and my cohort nonsense!

    Sorry, don't take offence. Just pulling your leg doc. :))

    By Blogger uglybaldie, At December 03, 2005 1:58 pm  

  • eh.. if NNT of 40 over 4 years, doens't that mean you'll only prevent 3 strokes the whole year instead?
    my stats also not very the power;)

    By Anonymous distinguished mediocrity, At December 03, 2005 6:41 pm  

  • There are three kinds of lies: lies, damned lies, and statistics.

    Benjamin Disraeli

    There are two kind of statistics the kind you look up and the kind you make up

    Rex Stout

    Facts are stubborn things, but statistics are more pliable

    Laurence Peter

    By Anonymous Anonymous, At December 03, 2005 9:08 pm  

  • Anon,

    Sorry, I need to clarify. Are you implying that:

    1. I am lying

    2. The figures I used are totally groundless

    3. Both of the above

    I don't mind anonymous comments or accusations, but I like to know exactly what I am being accused of.

    Thank you.

    By Blogger angry doc, At December 03, 2005 11:28 pm  

  • DM, I think you are correct.

    Three strokes a year then.

    But like I said there are other complications and patients with other conditions too. Afterall, there must be reasons why they are chronic patients.

    By Blogger angry doc, At December 03, 2005 11:52 pm  

  • no angry doctor don't be angry. I am just making a point that while statistics is a useful tool it cannot be used without human discretion. Ultimately the stats should be examined for flaws. For your post to be accurate you've made certain assumptions. Unless the assumptions hold true your stats' prediction would not be accurate. There is a limitations in stats. I am also sure that you are aware that although evidence based medicine relieves heavily on stats, people can manipulate it to look acceptatble. That is why when you are reading the journals you would want to know who did the trial. Whether it is the pharmaceutical company themselvse or some independent body. Look at the cox 2 inhibitors. Either they have a sampling error or somethings are swept under the carpet. Or perhaps the sample size is just not large enough to detect a signifcant amount of side effects.

    I apologise if I have angered the already angry doctor. :)

    From your post you seemed to be a rather principled doctor with strong guiding values. I respect you for your dedication in improving the healthcare system in Singapore. Well it is tough battle and often discouraging, but may the force be with you :) With all the societal pressure it is easy to veer to the dark side :)

    By Anonymous Anonymous, At December 04, 2005 12:52 pm  

  • Haha, anon - got you there! :)

    You are of course right, and you know how I feel about Vioxx.

    The figures I used are rough estimates, but I believe the order of magnitude is correct.

    Readers should remember what my motives are when I blog too.

    By Blogger angry doc, At December 04, 2005 11:07 pm  

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