What Labs Really do..., Part Two
Posted by Sten Westgard, MS
Earlier this month, we posted about an interesting survey of laboratory quality control practices. The study was so interesting, it's worth revisiting the topic.
Just to review, here's the citation:
Audit of internal quality control practice and processes in
the south-east of England and suggested regional standards.
David Housley, Edward Kearney, Emma English, Natalie Smith, Teresa
Teal, Janina Mazurkiewicz and Danielle B Freedman. Ann Clin Biochem
2008; 45: 135–139. DOI: 10.1258/acb.2007.007028 (subscription required)
What we'd like to point out in this post is what happened after the survey was completed. Based on the results, the authors of the study proposed a set of standards for quality control for the laboratories in their region:
- IQC policies should cover 24 hour period.
- Target values and ranges for IQC material should be assigned locally for each instrument. Manufacturer target levels and ranges should not be used.
- Labs should use IQC material from a third party source.
- Use EP5-A2 or equivalent to determine IQC values within each individual laboratory.
- Encourage method specific rules (single and multi) based on the required quality of the assay, and known method bias and coefficient of variation.
- Discourage inappropriate use of single rules, but when used ensure they have required degree of error detection.
- Review grades of staff accepting and rejecting IQC
- If IQC policies are robust, and the correct IQC with appropriate error detection is used, failed IQC should not be accepted (e.g. to continue processing patients' samples).
- For analysers that have multiple modules, each module should be assessed individually with IQC on each assessment.
For frequent visitors and readers of Westgard Web, few of these proposed standards should come as a surprise.
Just to find out a bit more, we contacted the authors of this study to ask about the reaction and impact of their findings. Dr. David Housley was gracious enough to send this reply:
"The standards we propose are our audit group's official guideline and have
been adopted as such for the region covered by our audit group. Unfortunately,
we have not done a re-audit yet, so we do not know how widely, if at all they
have been adopted, or if they have influenced practice. Anecdotally I think
things such as changes to policy to cover 24 hours and changes to ensure all
modules are tested have taken place. One thing the audit / paper did achieve
however, was an increased awareness of IQC and the need to review practice. I
am not aware that the ACB or our National Audit Group have proposed them as
National standards. If the other regions that have contacted me with an aim to
undertaking their own audit complete their studies, I would imagine these
standards (or similar) will progressively spread.
"In general people seem to fully appreciate the important concept of IQC,
but fail to understand it sufficiently to make it work in practice. I think the
biggest problem in IQC is the belief that repeating the test is an appropriate
course of action, and if the repeat result is within limits, it is safe to
proceed and excludes an analytical performance issue. I suspect that the single
2SD rule is largely the decision tool used for judging a repeat (or often
multiple repeats) to be OK, and of course promotes the concept that the IQC is
out for statistical reasons and not because of true performance issues."
[personal communication, 3/5/2009]
[personal communication, 3/5/2009]
It's heartening to see such recommendations coming from an Audit and Quality Assurance Group. Somewhere in the world QC is still being taken seriously. If a similar survey of US laboratories were conducted and found similar results, I'm afraid our US regulators would generate the opposite recommendations: that IQC is too hard and thus, we need to dismantle IQC and replace it with something that the laboratories can more easily achieve (i.e. Equivocal QC).
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