Now that the waves have abated a bit after I threw the half-brick of 
my friend John's contributions into the pond of discussion on GM/GE 
foods, perhaps I could contribute another issue on which I'd welcome 
feedback.  It does follow on to some extent from recent postings 
about healthy living outlets, but it also relates to my own 
professional involvement in "near patient testing"  (US terminology  
is "point of care testing").

POCT in hospitals & GP surgeries has existed for a long time, 
ranging from simple qualitative dipstick tests to analysers in 
critical care areas such as ICUs.  These are not without problems - 
patient deaths resulting from use of poorly maintained equipment by 
untrained medical & nursing staff resulted in the issue of 2 Hazard 
Notices by the Dept of Health a few years ago, recommending that 
such equipment should be supervised by Pathology staff, who should 
train users in its use and ensure that proper Quality Control and 
Assurance systems are in place.  This makes the operation of POCT 
safe, but expensive.  The Medical Devices Agency also issue reports 
on equipment and have recently been interested in the wider aspects 
of how POCT is used.

Advances in analytical technology are introducing new diagnostic 
possibilities in the lab, but are also simplifying equipment for some 
tests so that they can be done outside the lab, by people who are not 
scientifically trained - eg health food shop staff and people 
offering tests as a business.  (Some pharmacists offer tests - they 
are, of course, health professionals).  If equipment is properly 
maintained, with QA in place and proper advice/counselling available 
to purchasers, then there's little danger, although from a quality 
point of view, better advice is likely to be available from GPs, who 
would know the person's full clinical picture and could order any 
necessary diagnostic tests from the local lab (free of course). 

There have been recent prosecutions over improper use of such 
extra-laboratory testing, but there are wider concerns.  Many 
people - not just non-scientists - are surprised to learn that 
individual tests rarely give 100% definite answers (an exception 
might be a pregnancy test, which of course would be interpreted in 
the context of other evidence). There are false positives and false 
negatives inherent in the whole testing process, and in clinical 
biochemistry at least, diagnosis is generally made from the results 
of several tests which are interpreted within a clinical picture plus 
consideration of prevalence (application of Bayes Theorem).   An 
example is blood cholesterol levels and cardiac risk - fine 
(assuming that the result is analytically OK) if interpreted along 
with smoking, blood pressure, family history, obesity and exercise, 
but in commercial situations it often isn't and people can be 
inappropriately reassured.

Biochemical screening for osteoporosis is a recent one causing 
concern - there is no effective single biochemical test for this (as 
far as I'm aware a bone density scan is the best test anyway) and 
there are reports of worried patients going to their GPs after 
getting some commercial test results which suggest that they have a 
problem (why didn't they go there in the first place?).

There are lots of other examples - but what do you think;- would you 
buy a commercially offered screening test?  If so, why?  If not, why 
not?  Is this sort of test availability - which is likely increase - 
a good or bad thing?

Dr MJ Pearson
Department of Chemical Pathology & Immunology
Old Medical School
Leeds General Infirmary (Leeds Teaching Hospitals NHS Trust)
LEEDS LS1 3EX

Tel 0113 392 3945


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%