My Dominant Hemisphere

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Quantifying Medicine – A Tricky Road

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I have been really enjoying Feinstein’s “Principles of Medical Statistics” the past couple of days. And today I felt like sharing a nifty and pragmatic lesson from the book. Now I’d love to put up an entire chunk from the book right here, but I’m not sure if that would do justice to the copyright. So I’ll just stick to as little of excerpt as possible. But to honestly enjoy it, I recommend reading the entire section. So grab yourself a copy at a local library or whatever and dive in. The chapter of interest is Chapter 6 in Unit 1. Towards the end, there’s a section that goes into interesting detail as to the merits and possible demerits of quantifying medicine. To demonstrate the delicate interplay of qualitative and quantitative descriptions in modern medicine, the author quotes a number of research studies that investigated how qualitative terms like “more”, “a lot more”,  “a great deal”, “often”, etc. meant different things to different people. They were able to do this using clever research designs that allowed them to correlate a given qualitative term and its corresponding quantitative estimate and they did this for different groups of people – doctors, clerks, etc. Frustrated at the lack of a consensus on the exact amount or probability or percentile/percentage and so on, of mundane terms like the above, one scientist even thought of a universal coding mechanism for day to day use. What frustrations you ask? One example is where an ulcer deemed “large” on one visit to a doctor at the clinic could actually be deemed “small” on a subsequent visit to a different doctor, even though the ulcer might have really grown larger during this time.

It is quite clear then, that qualitativeness in medicine often seems like a roadblock of some sort. Not to dismay however, as Dr. Feinstein ends this chapter with a subsection called “virtues of imprecision”. I found this part to be the most worth savoring. He describes some of the advantages of using qualitative terms and why on some occasions they might in fact be better in communication:-

  1. Qualitative terms allow you to convey a message without resorting to painstaking detail. Detail that you might not have the ability to perceive or compute.
  2. Patients find qualitative terms more intuitive and so do doctors.
  3. Defining or maybe replacing qualitative terms with quantitative ones, potentially could lead to endless debates on where cut-offs would lie (why should 1001 come under ‘large’ and 1000 under ‘small’…hope you get the drift).
  4. Many statistical estimates like survival rates, etc. come out of potentially biased studies and it may be wrong to say that “good” survival is say 90% in 5 years and “better” is 99% in 5 years. Which is to say, that it may be wrong to give an impression of precision when in fact it isn’t present.
  5. Perhaps the most important and pragmatic lesson he gave, was about the false sense of security/insecurity numbers could give to either patients or doctors. Naivety plays devil here. He demonstrated this using the cancer staging system. Each cancer stage has some sort of survival statistic attached to it, right? So for example (the numbers here are solely arbitrary), for Stage I cancer, the 5-year survival is 90%. Stage III cancer in contrast is given a 5-year survival probability of 40%. A patient with Stage III cancer, will be given this information by his or her physician and management plans will be made. What the physician might not realize is that if Stage III is split into further sub-stages, say from Stage III-substage 1 to Stage III-substage 10, the survival probabilities range from 75% to 5%. The 40% statistic is the ‘average’ and may not be sufficiently relevant to this particular patient, who for all we know could belong to Stage III-substage 1. So, broad statistical numbers are not necessarily pertinent to individual cases.

Oh and did I mention excerpt? Ah, never mind. I’ve covered most of the juice paraphrasing anyway 🙂 .

Hope you’ve found this post interesting. And if you have, do send in your comments 🙂 .

Readability grades for this post:

Kincaid: 8.8
ARI: 9.1
Coleman-Liau: 11.8
Flesch Index: 62.3/100 (plain English)
Fog Index: 12.2
Lix: 40.4 = school year 6
SMOG-Grading: 11.3

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Written by Firas MR

April 24, 2008 at 1:50 pm

6 Responses

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  1. Looking at the numbers in the picture, that’s a one big man. Am I right ?

    And that guy works for a Canadian Company that uses Canadian health insurance eh. 😉

    Should I find it odd that the insurance company used metric numbers to measure height and weight ?


    April 24, 2008 at 3:21 pm

  2. Jaffer:
    LOL! What an astute observation 🙂 . I don’t know about the Canadian company thing. It certainly seems possible! Metric numbers are the norm in Commonwealth countries I guess.

    I was just wondering how much of this article you could grasp 🙂 . I try to write stuff so that it generally should be easy to understand for people outside of medicine. The intended audience for this article are obviously medics, but it should appeal to laymen’s senses too.

    Firas MR

    April 24, 2008 at 5:13 pm

  3. I looked at the picture, I skipped reading the article and went straight to the comments. Is that OK for honesty ?

    I don’t think too much about the medical details you go into, and I read this article from a very general perspective.
    I can think of numerous examples where Quality vs. Quantity really matter.

    In short, this article makes perfect sense.


    April 24, 2008 at 5:43 pm

  4. Jaffer:
    LOL at skipping the article 🙂 . I’m planning on hopefully writing a post of the more general kind soon. Perhaps Ubuntu or technology related 🙂 .

    Firas MR

    April 24, 2008 at 5:54 pm

  5. About metric numbers, although Canada switched to metric in 1970s, adaptation has been painfully slow !

    We buy Gasoline in Litres, measure speed in Km and measure temperature in Celsius.

    But we measure weight in pounds, height in feet and inches and area in sq feet !

    After taking a look on Wikipedia and finding that SI dominates in the Health care system, I shouldn’t find it odd after all,


    April 24, 2008 at 5:55 pm

  6. Jaffer:
    Wow, that is something I didn’t know about!

    Firas MR

    April 24, 2008 at 6:01 pm

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