There are a few important aspects of testing that are missing here. Or 
maybe they are there, but are not explicit enough. Or maybe I'm the one 
missing the point. But anyway, here are some of my thoughts about the list.

First, there is always the temptation to please the patient who thinks 
that more tests equals better medical treatment.

11. Thou shalt not order a test just to placate thy patient.

Second, there is a financial conflict of interest when a doctor buys 
expensive new machinery.

12. Thou shalt not order a test just to help make payments on thy new 
diagnostic equipment.

Third, there is a tendency to notice the one spectacular failure and 
give it disproportionate influence.

13. Thou shalt not let a single anecdote dominate thy thinking.

Fourth, there's a tendency to slavishly follow previous practices.

14. Thou shalt not order a test just because that's always what's been 
done in the past.

You need, of course, to keep this at ten commandments. You might combine 
#4 with #5 or with #6. Or you could incorporate #11 with one of these. 
You could also combine #12 with #3 or #8. #13 is probably just an 
additional elaboration on #10. #14 might fit in with #9.

Also, the concept of predictive value in #1 is a bit muddled. It's 
perfectly fine to accept a PPV of 10% in a setting where additional 
follow-up is cheap and the consequences of false negative is extremely 
severe. The classic example is diagnosing cervical fractures in the ER. 
There is a cost to unnecessary x-rays, but it is still relatively small 
when compared to sending someone home with an undiagnosed problem. These 
people come back three days later in a wheelchair and with a team of 
lawyers accompanying them.

Good luck. When you finalize this list, please make sure it gets 
published someplace prominent.

Steve Simon, [log in to unmask], Standard Disclaimer.
Sign up for the Monthly Mean, the newsletter that
dares to call itself average at www.pmean.com/news

On 1/7/2012 9:40 PM, Michael Power wrote:

> Thou shalt obey the following ten Commandments for testing, whether it
> be for ruling in a diagnosis, ruling out a diagnosis, assessing risk or
> prognosis or response to treatment, or for monitoring for adverse
> effects and deteriorating status.
>
>
> Thou shalt understand testing in its broadest sense; it includes
> history, examination, laboratory tests, imaging investigations,
> diagnostic procedures, and therapeutic trials.
>
>
> When a commandment is impractical or impossible, thou shalt treat it as
> an aspiration and do thy best.
>
>
> For I am thy patient and client, whose interest thou shalt serve, and no
> other.
>
> 1.*Evidence.* Thou shalt not take the evidence in vain, but test
> according to the best estimates of prevalence, positive predictive
> value, and negative predictive value. If the predictive value of a test
> is less than about 50%, toss a coin — it will be cheaper and as useful.
>
> 2.*Application of evidence. *Thou shalt not overly rely on test results,
> but shalt apply your clinical judgement after clinically assessing your
> patient and critically appraising the evidence, taking into account its
> precision, risk of bias, and directness of applicability.
>
> 3.*Cost-effectiveness.* Thou shalt not covet thy neighbour's graven
> image technology (PET scanner, fMRI scanner, high resolution ultrasound
> scanner), nor his micro-array genetic tests, nor his direct to consumer
> testing business, nor his yacht, nor any thing that is thy neighbour's,
> but thou shalt practice cost-effective testing. If a cheaper test will
> be as useful, use it.
>
> 4.*Patient-education.* Thou shalt help thy patient understand that many
> diseases are gradual and progressive, analogue processes not digital
> events. Diagnostic thresholds and limits are chosen for convenience, but
> create artificial categories that may be misleading if they are
> misunderstood as boundaries between having and not having a disease, or
> having and not having a risk.
>
> 5.*Joint decision-making.* Thou shalt help thy patient understand the
> limitations of tests. Many conditions cannot be diagnosed or excluded by
> tests (for example dementia, wellness). Tests can be falsely positive or
> falsely negative or inconclusive. No test can give a precise prognosis
> for survival or other probability, and interpretation of prognostic
> tests should consider both the average (median or mean) and the
> distribution in the comparator population. Thou shalt remember that test
> results can in themselves be distressing or harmful. For these reasons,
> decisions about testing are best made jointly with thy patient.
>
> 6.*Patient-centred care.* Thou shalt not take thy patient’s needs in
> vain, but before testing help them understand what the management
> options are for a positive, inconclusive, or negative result, and what
> support is available should the result be distressing. Honour the
> elderly patient, for although this is where the greatest levels of risk
> and temptation to test reside, so do the greatest needs for avoidance of
> useless and harmful testing.
>
> 7.*Efficiency.* Thou shalt not repeat a test when the result is already
> available or the result will not change (as with genetic tests or when
> the clinical indications have not changed). Thou shalt ensure that the
> results of tests you have ordered or performed are clearly recorded and
> available or communicated to any other physician caring for thy patient.
>
> 8.*Ethics.* Thou shalt not use testing as a defence against legal
> action, or as a placebo, or as a delaying tactic while nature takes its
> course, or to avoid confronting the limitations of curative medicine
> when care, support, or palliation is appropriate.
>
> 9.*Education and engagement.* Thou shalt help thy trainees and junior
> colleagues understand that they should investigate having considered the
> needs of their patients and the performance of the tests. The reason for
> testing should not be that it is routine, or policy, or what they
> imagine their consultant/attending expects.
>
> 10.*Gnothi seauton. *Thou shalt know thy cognitive limitations. Thou
> shalt try to avoid the fallacies of assuming that all abnormal results
> are important or that an abnormal result is sufficient to explain
> symptoms. Thou shalt consider the whole picture, and the differential
> diagnosis, and the possibility that tests bear false witness.
>
>
>
>
>