The mystique of blood tests

Sometimes patients arrive at the health centre clutching a fistful of blood test results.  They feel unwell,  so go and get tests done themselves and want me to tell them what is wrong with them.  Often I have to send patients for tests to help diagnose and treat their illness.  This is all very well, so long as the tests chosen are relevant and the results are reliable and accurate.  Unfortunately, this is often not the case.  Patients come, having done completely the wrong tests.  Laboratories give erronerous results.  Sometimes it is hard to see the wood for the trees.   

The results can be very misleading.  One very pale lady, for example, had her blood tested for anaemia at the laboratory I usually recommend.  The result came back normal.  I then sent her to another laboratory, as I did not believe the result, and the result showed moderate anaemia.  Did they test the right sample at the first laboratory?  Or are they giving wrong results to everyone through a badly calibrated machine or poor quality reagents?

I later had a woman needing testing for coagulation of her blood as she was on blood thinning treatment.  We were getting consistently low results at one laboratory, so she went to a different one to check.  The second one gave her a completely normal result, showing no blood thinning at all.  This was clearly wrong - and dangerous - imagine if she were about to be undergoing surgery.  An erronerous blood result, showing no blood thinning, could have meant she bled to death on the operating table.  

Patients believe test results define their health.  They never question them.  It is the mystic of a magical process that reveals their inner maladies and brings them to light.  Take ultra-sounds for example.  Pharmacies here offer free abdominal ultrasounds and diagnose "fatty liver" left, right and centre.  Patients are always telling me they suffer from it, and that the pharmacy sold them some wonder drug that cost them an arm and a leg.  Sometimes it seems not to be very different from the witchdoctors who pass an egg over a patient to diagnose their "evil eye" or "shock".

I find I need a healthy dose of scepticism and sharp clinical skills when trying to interpret results.  I always need to start by listening to the person sitting in front of me and examining them carefully.  Only then will I open the test results they hand me with such reverence, expecting all will be made known.  If the results are different from what I was expecting, I send them to double check.  Tests are not infalible.