This is a talk on life as well as on common medical controversies.
People are generally well meaning.
Treat others as we would like ourselves to be treated is a motto that most if us work by.
So where does it go wrong?”
Well I guess we all like to be treated in different ways.
I like to think on the alternatives in life, in the choices we make, why we make them and the consequences both obvious and hidden.
Diabetes
Coeliac disease
Vaccinations.
Screening tests.
The big ones here are Prostate Cancer, Breast Cancer and Bowel Cancer. Why screen at all?
A silly question which carries a sting in the tale.
To detect cancer, and other diseases early enough to be able to do something about them.
Disease exist in our community that develop over time and cause serious health problems.
Tests exist to detect these diseases.
Simple enough.
It has nothing to do with preventing such diseases.
Having a screening test does absolutely nothing to prevent a disease occurring or even worse being present when you do the procedure and being missed.
Who has screening tests. People at risk.
Family History . Population History. Occupational History , Exposure History.
A screening test has to be useful, It has to have a high sensitivity and high specificity. This means that it is able to detect problems early enough [sensitivity], and accurately enough [specificity].
It has to diagnose conditions that are dangerous, reasonably common and hopefully treatable without causing problems of it’s own worse that what one is trying to treat, in other words it has to be safe.
Screening can by done by endoscopy, faecal and urine sampling, Blood tests and Radiological procedures such as X-Ray, CT , Bone scan and MRI to mention a few.
Pitfalls of testing.
Cost , the equipment is all there but some are very expensive. New tests in particular. Cheapest but still not cheap are the Urine testing for sugar protein and blood
Time, Some tests like 24 hour ECG’s and bone scans can take days to do
Patients often have limited time themselves to do the test in.
Discomfort
Danger
Loss of results
Wrong results
Statistical use of the results.
Endoscopy, looking inside the body through a tube, is a good way of detecting cancers. Lung, throat, Stomach, bladder and bowel cancer can be detected this way.
Who here volunteers to have a colonoscopy every 6 months? or a bronchoscopy.
Questions
Would you have all of them every 5 years? What would be a good age to start.
Not many , Reasons discomfort, embarrassment, time , risk
Having a procedure often involves having an anaesthetic, The risk of dying from an anaesthetic increases with age and other medical conditions but can occur in healthy young people as well. Somewhere between 1 in 5,00 to 1 in 10,000. As well as the risk of the procedure itself. Perforation of the bowel and bladder, rupture of the oesophagus, damage to the vocal cords, aspiration and pneumonia, Urethral stricture with a urethroscopy .
wrong diagnosis, no diagnosis, missed diagnosis and lost specimen.
Import of the result and use of statistics. This is one that I have great difficulty in understanding.
Say that a mammogram will diagnose a breast cancer with 95% accuracy.
You have a patient who comes to you with a positive result from a screening procedure.
What should you tell her. As the patient if you are told it has a 95% accuracy what does this mean.
Murky waters lie ahead. The false positive paradox is a statistical result where false positive tests are more probable than true positive tests, occurring when the overall population has a low incidence of a condition and the incidence rate is lower than the false positive rate. When the incidence, the proportion of those who have a given condition, is lower than the test’s false positive rate, even tests that have a very low chance of giving a false positive in an individual case will give more false than true positives overall.[2] So, in a society with very few infected people—fewer proportionately than the test gives false positives—there will actually be more who test positive for a disease incorrectly and don’t have it than those who test positive accurately and do. The paradox has surprised many
Low-incidence population
| Number of people |
Infected | Uninfected | Total |
|---|---|---|---|
| Test positive |
20 (true positive) |
49 (false positive) |
69 |
| Test negative |
0 (false negative) |
931 (true negative) |
931 |
| Total | 20 | 980 | 1000 |
Now consider the same test applied to population B, in which only 2% is infected. The expected outcome of 1000 tests on population B would be:Infected and test indicates disease (true positive)1000 × 2/100 = 20 people would receive a true positiveUninfected and test indicates disease (false positive)1000 × 100 – 2/100 × 0.05 = 49 people would receive a false positiveThe remaining 931 tests are correctly negative.
In population B, only 20 of the 69 total people with a positive test result are actually infected. So, the probability of actually being infected after one is told that one is infected is only 29% (20/20 + 49) for a test that otherwise appears to be “95% accurate”.
A tester with experience of group A might find it a paradox that in group B, a result that had usually correctly indicated infection is now usually a false positive. The confusion of the posterior probability of infection with the prior probability of receiving a false positive is a natural error after receiving a life-threatening test result.
As breast cancer in the general female population is a relatively low incidence disease the outcome of a false pasotive is quote high.
Herein another risk, traumatising people with false positives and equivocal results, one does not like to rule out cancer conclusively if some doubt is present leads to up to 15% of women who have a screening mammogram having to undergo further procedures , usually invasive biopsies with pain discomfort, bruising and rarely infection.
Not to mention the 5% who have a false negative, also not as common as it sounds.
Finally Cancers are incredibly small, incredibly fast growing and have usually been present for 6-18 months before getting big enough to be detected. So one may have a bowel or breast cancer present at the time of screening, have it missed due to its size and present with a large cancer 6 months later.
Finally removal of the cancer does not guarantee that the cancer has been successfully treated. Cancers can spread [metastasize] before removal. Melanoma is an example.
In the other hand BCC usually grows locally only but very aggressively, Some poor souls it does metastasize. SCC has a slightly higher spread rate than BCC which is why it needs removal and follow up.
Prostate Cancer is an enigma which is treated in an ageist and sexist manner by most people and the medical profession. It has none of the media appeal of breast cancer, the young mother cut down in her prime with dependent children and husband.
Instead an older man has a blood test at the insistence of his wife and gets told his PSA is up. Still the hope of a wrong diagnosis. Multiple other causes. He may have an infected prostate, very high reading 20+ , treatable with antibiotics. He may have BPH [benign prostatic hyperplasia] an example of the word benign not really meaning what you think it does. At least it is not cancer and after 15 hours of agony not being able to pass urine a catheter is inserted by a first year resident, hopefully in the right place with no perforation and one is on the way to a TURP or onion peeling from the inside with the risk of loss of sexual function, not that it matters for an old guy anyway.
Next he has a trans rectal biopsy with 12 needles taking samples then he is told the bad news.
Bad news? We are doing nothing for you. Most men with prostate cancer are so old they die with it not because of it. Prostate cancers can be very slow growing [Which type have I got? We don’t know] Your life span is to short to worry about it. The treatments cause loss of sexual function, baldness and you will go blind.
Only joking.
The facts are that prostate cancer is treatable, One can have surgery, radiotherapy or a combination.
Prostate cancer does spread rather early so prevent developing cancer or to
Males generally get cancer later than females
I would like to present an over view of the screening dilemma.
I will reference my talk to certain illnesses and conditions that are common in the community and a few that are not. Along the way I will mention several misconceptions with these conditions. I welcome relevent questions but will deal with most in the breaks or afterwards.
Medicine is concerned with the health of individuals first and then with health of populations. It consists of both diagnosis and treatment of medical conditions. Originally these were of the body but those of the psyche then followed. As new treatments and medications were developed medicine became an enlarging field with more expectations of keeping people healthy.
Means of diagnosis improved. At first these were only applied to people with illnesses, but then the ability to look for problems ahead of time became apparent and screening was born.
Screening is a form of diagnosis that came late to medicine. Tests on urine for protein and blood were possible. Blood tests began being used at the start of the 19th century and X-Rays were developed.
Progress was slow so much that the routine testing strips we know use routinely with 10 tests on were still a 2 strip novelty 40 years ago ..
CXRays for TB detection were among the first general screening projects undertaken.
This dreaded disease, still present today, was reduced a hundred fold with detection treatment and isolation. Screening was abolished in the 1970’s in Australia. for 3 reasons which are still valid today. Cost, Radiation exposure [side effects] and near elimination of the condition. One funny twist of fate due to litigation and over investigation a large percentage of the population still have CXR’s for other reasons which equate to a de facto screening program.
The modern health problems are those of living longer, diabetes cancer and heart disease [stroke]. These conditions all increase with age and all reduce life expectancy greatly. They have an enormous impact at any time but more so when the sufferers are young.
Ao to screening.
The ideal screening test is something non invasive, very reliable easy to do and producing a treatment outcome beneficial to the patient.
Bowel Cancer.
A sample of poo, well 2 or 3 actually a day apart preferably after avoiding meat in the diet an