The main purpose of EQA is Accuracy check. In practice this purpose is not
served in the majority of EQA programs due to lack of commutability of the
commercial materials in use. The issue of commutability is resolved
conveniently through grouping participant laboratories in EQA programs into
method and/or instrument groups. The assumption behind these groups is that
all method or instrument in a group will respond the same way when EQA
material is presented to them. In other words, they will all, in a group,
suffer the same matrix effect to the same degree. This will allow easy
comparison of the group. The problem is that material that causes matrix
effects is not suitable for Accuracy evaluation of methods. This material is
not suitable for intermethod comparison.
What are we really evaluating with EQA that use commercial materials?
Commercial QC materials are materials with stabilizers, reduced matrix and
also spiked with some analytes. The fact that the only benefit one gets from
EQA is through comparison with one's peers based on method or instrument
group, one can deduce that the main purpose of most of these EQA programs is
to evaluate:
a) The Manufacturers: To check if manufacturers are fair in
the distribution of their reagents, calibrators etc. to their customers
without indiscriminate introduction of reformulated reagents. This also
checks the uniformity in the quality of reagent production.
b) The method/Instrument Operator: To check the way the
laboratory uses the technology the way it is meant to be used, just like the
peer group.
David has a point which needs further discussion. Without fiddling, he is
already participating in a peer group of laboratories, what will be the
additional benefits derived from the individual peer laboratory
participation in the EQA program other than it being a formal program?
****************************************************************************
**********************************************
Dr. PD Rambau
Chemical Pathologist
QA/Operational QC Division
Lancet Laboratories
Tel: +2711-3580800
Fax: +2711-3580967
e-mail: [log in to unmask]
Web Address: http://www.lancet.co.za
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-----Original Message-----
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of Janice Still
Sent: Tuesday, August 05, 2008 11:48
To: [log in to unmask]
Subject: Re: Cross site EQA
Mike,
I takeyour points but...
In an ideal world we would all work in well-designed, spacious labs with
good lighting , ventilation and with analysers grouped together, where the
air conditioning keeps a constant temperature across the whole lab; where
no-one leaves the fridge or freezer door open; where no-one takes the wrong
lot off the shelf.However, for most of us the reality is far from this, with
poor air conditioning that struggles to keep within 5 degrees of the optimum
and with a temperature gradient across the lab so no two instruments are at
the same temperature, where one instrument is two years older than the rest,
where one instrument is at the satellite lab ten miles down the road, and
where the staff are human beings with all the faults intact.
By tweaking I am guessing that David was referring to the complex
choreography that takes place when you attempt to calibrate a number of
instruments on the same day and at roughly the same temperature so they are
all on the same hymn sheet. We spend hours calibrating, recalibrating,
watching the IQC and things still go wrong. The temptation is always there
for people to interfere, often with the best of intentions, and alter some
parameter or assigned value, or change a reagent, and then forget to record
it or even mention it, and it hasn't flagged the IQC and the first you know
about it is when you get an EQA report with an outwith value.
How would you decide which analyser was "the one" to get the EQA? The
oldest, as it has more chance of faults, or the newest, as it is more likely
to give the "right" result? Would you rotate them on a monthly basis? How
could you pick up trends?
David's proposal merits some discussion, and labs should all be carefully
looking at their EQA participation to avoid unnecessary duplication and
expense.However, it would be a brave lab that would try this proposal on
with CPA, and I suspect that a critical non-compliance would be winging its
way pretty quickly. Mrs. J. Still,
POCT Manager,
Biochemistry Dept,
Watford General Hospital. 01923-217998.
The views expressed in this message are personal and do not reflect West
Herts NHS Hospitals Trust policy.
----- Original Message ----
From: Hallworth Mike (RLZ) <[log in to unmask]>
To: Janice Still <[log in to unmask]>; [log in to unmask]
Sent: Monday, 4 August, 2008 5:11:21 PM
Subject: RE: Cross site EQA
Hi Janice
I think you've missed David's point. The difference is that lab analysers
have frequent and rigorous IQA checks which POCT analysers generally don't.
These are used to ensure that the right results are going out - and to do it
BEFORE they go out, which is rather better than waiting for the EQA to come
back, when it is a bit late...
In this situation, EQA is telling you primarily about differences in
method/analyser bias rather than poor consumables, instrument malfunctions
etc. And there is a good argument for registering only one analyser for that
purpose, and using the IQA to monitor differences between analysers (I'm not
getting into the 'fiddle factor' debate!!).
I think David raises a legitimate point which merits serious discussion, not
dismissed as you have done.
Mike
-----Original Message-----
From: Clinical biochemistry discussion list
[mailto:[log in to unmask]] On Behalf Of Janice Still
Sent: 04 August 2008 16:55
To: [log in to unmask]
Subject: Re: Cross site EQA
David, I can only assume that you have your tongue firmly in your cheek. If
not, then you have successfully taken my breath away! The analysers may be
the same, the cartridges and reagents may be the same,but what the USERS do
to them is certainly not the same.I am also concerned by your mention of
"tweaking". I thought that we had all abandoned fiddle factors long ago.
Every single one of my analysers is individually EQA enrolled and I would
not have it any other way. Recently the EQA showed a sudden negative bias on
PCO2 on one analyser, which was eventually traced to the sample path not
being kept at 37C. If I was only looking at EQA on one analyser, how would
this have been picked up? If you decided to take the lab as your "typical "
instrument, where it is looked after by qualified BMS staff, what hope
mwould there be for the instrument in A/E and all the misuse that it
gets?You simply CANNOT blithely assume that one size fits all. How do you
know that consumables have been stored correctly, or have been used before
the sell by date? At the end of the day the whole object of EQA is to ensure
that the PATIENT gets the right result on the instrument that their blood is
analysed on. Yes it is expensive. Live with it. And I hope your patients do.
JanMrs. J. Still,
POCT Manager,
Biochemistry Dept,
Watford General Hospital. 01923-217998.
The views expressed in this message are personal and do not reflect West
Herts NHS Hospitals Trust policy.
----- Original Message ----
From: David Robertshaw <[log in to unmask]>
To: [log in to unmask]
Sent: Monday, 4 August, 2008 2:09:19 PM
Subject: Cross site EQA
The Leeds/Bradford Biochemistry service has four sites all with the same
analytical equipment using the same reagents and IQA. IQA performence is
compared regularly and used to "tweak" the analysers to get the same answers
across all sites. Why then do we need to enrol all four sites in the same
EQA scheme?? If one analyser is performing satisfactorily compared to the
"National norm", (as evidenced by EQA), and the other analysers compare
satisfactorily with that one why repeat the EQA analysis?? I believe many
hospitals with several Blood Gas Analysers of the same make will only EQA
one and accept performnce of the others on the basis of IQA. Could this
principle not be applied far more widely particularly in the light of
networking and the fact that equipment, reagent production, cartridge
manufacture and standards are common across many sites.
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community working in clinical biochemistry.
Please note, archived messages are public and can be viewed
via the internet. Views expressed are those of the individual and
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