It's only fair to share…

Always be wary of a call to do a “simple blood test”. There is no such thing. Whilst taking blood out of a vein is simple, the results are never simple and a “simple blood test” can start a chain of events, which are far from simple.

The worst example is the call to check for prostate cancer with a “simple blood test”. I will come back to this shortly.

In a nutshell, our capacity to find things on testing has advanced rapidly but our ability to interpret what we find has not advanced as quickly. Furthermore the tendency to lower thresholds for “disease” pulls more and more people into the medical net. A “simple blood test” can convert a healthy person into someone with a disease or even more profitably, someone with a risk factor.

It is salient to remember that most tests we have were designed to detect disease when used on a population group where disease was suspected. As all tests have statistically defined normal ranges, for every test done, some 5% of people who have nothing wrong with them will have an abnormal test result.

So the more tests that we do the more abnormal results we get and the more tests that are done to prove that nothing was really wrong in the first place. This can all be justified if there was a net benefit overall in terms of better long-term outcomes for most of the people having the test.

After looking at data over 20 years the US Preventative Services Taskforce has formalized its previous advice that there was no benefit for routine PSA testing on healthy men. On the surface this sounds counterintuitive. Surely finding more cancer early means saving lives.

Except that the facts do not show that the routine PSA screening does this.

1)   The test is not diagnostic of prostate cancer and can be raised for other reasons. The inventor of the test described it as a “toss of a coin”. It was originally devised as a tracking test for established cancer.

2)   Many men will die with, not of prostate cancer. Some 70% of seventy year olds have prostate cancer cells on autopsy. Even for men aged between 40 and 60 the figure is 33%.

3)   This highlights the point that we do not actually know what an abnormal test result means!

4)   In turn a raised PSA generally leads to further invasive procedures such as a biopsy. In this there are risks of bleeding and infection and even then the results may be vague.

5)   Thus leading to treatment of many cancers, which if left alone would not shorten life or impair function. The problem being we do not know which is which.

All this might be justifiable if there was a significant likelihood of men undergoing testing having a good chance of living longer than those who do not. Previous large European trials have not shown this to be the case. And the USPTF figures show the following –

1)   For every 1000 men having routine testing one man will have life saving surgery.

2)   For every 3000 men having routine testing one will die prematurely due to complications of treatment.

3)   For every 1000 men tested up to 43 will suffer serious harm. Some 30-40 will become impotent or incontinent or both. Two will have a serious cardiovascular event (like a heart attack) due to treatment and another may get a blood clot in the leg or lungs.

For every three lives “saved” one will be lost and over 100 will suffer serious complications! 

Anyone want to volunteer to be the fall guy?

The recommendations will attract criticism, much of which will come from those who earn a living treating and testing for prostate cancer and their representative organizations. Some will put a political spin on this and call it rationing. This is complete nonsense as nobody is barred from having the test.

Some will complain that this will cause doubt in the mind of men about testing as one caller on my morning slot with Paul Murray did this week. I hope it does create doubt and that more thought is given to having a “simple blood test”.

Ideas in medicine change. We no longer use leeches. The PSA as a screening test was never actually trialed to see if was beneficial. Now with hindsight we can see that it is not. Worse than that more men are harmed than helped.

Each man must make a decision about testing based on his individual circumstances. One day there may be a way of detecting prostate cancers, which would be a threat to life, without so much collateral damage. Until then, we need to consign routine testing on all men just because they are male and have reached a certain age to join the leeches in medical history.