A
few days ago I mentioned that I need to look at ways in which I can seek to
improve the quality of the service we offer. Here's something inspired by a
little episode in the lab this afternoon. It might come to nothing, but the
intention is good...
- On
the one hand having a blood sample taken isn't something that is done lightly.
It hurts.
- On
the other hand providing poor quality blood test results can adversely affect
patient treatment... and that hurts too.
It
is possible to obtain blood count results from under-filled sample bottles. In
fact the manufacturers of most anaylsers pride themselves on just how small a
sample can be run. But should we run them? The EDTA anticoagulant in the
bottles causes swelling of red cells. In a correctly filled blood sample bottle
this swelling is to an expected uniform amount (as we have a precise amount
of blood and a precise amount of anticoagulant) and therefore isn't a pre-analytical variable
of importance. However in an underfilled sample...
How
many times have you looked at cumulative blood count results and seen that
someone's MCV which has been constant for over a week suddenly jump up by ten
per cent; only to find an under-filled blood bottle?
Does
this sudden rise in MCV matter? Obviously it does. This issue could lead to a
case of iron deficiency or a case of thalassaemia being missed.
So
what do we do? Reject all blood count samples that are underfilled? Of course not.
The haemoglobin level and cell counts in the sample are unaffected. It is just
the MCV which rises (and consequently the parameters calculated from that).
So given an under-filled sample we just report the haemoglobin and cell counts
on underfilled bottles and report the rest as "unable to provide a full
set of results due to an under-filled sample having been received"...
But
following a difference of opinion this afternoon on whether or not the amount
of blood in a sample was low enough to warrant being called under-filled, this
begs the question of precisely how under-filled is "under-filled"?
Back
in the day we would have got scientific at this point. We really would have got
out a needle and syringe, exsanguinated the trainees, created a range of blood
samples from "properly filled" to "barely a drop of
blood in the bottle" and had a range of samples filled to
half-millilitre intervals in between, and seen for ourselves how the MCV
changes. With loads of sets of data (from loads of different exsanguinated trainees) we
could have determined at which point the EDTA-induced swelling of red cells becomes
significant.
But
nowadays we (sadly) can't just stick needles into trainees. We need to
get formal ethical approval from all sorts of committees before we can even
consider this sort of experiment... (for which the trainees are probably
grateful)
I've
suggested to the boss that she might like to investigate how we get this
approval. We'll not tell the trainees about this just yet... They tend to run
and hide when this sort of thing happens. I know I used to...
