Quotes

The greater the ignorance the greater the dogmatism.

Sir William Osler

British (Canadian-born) physician (1849 - 1919)

"He uses statistics as a drunken man uses lamp posts - for support rather than illumination.”

Andrew Lang (1844-1912)

This list was created in a collaborative process on the EBHC listserve.

Ten Commandments for testing – by Michael Power, Richard Lehman and others

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 (Greek for "know thyself"). Thou shalt know thy cognitive limitations and biases. 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 against thy patient.