New Download: Sigma-Metrics Tool (and audioconference presentation)
On September 4th, 2008, Dr. Westgard spoke as part of the AACC audioconference on "New Directions in Laboratory QC" - which was subsequently quoted in the Clin Lab News article on Risk and CLIA. We are pleased to make available Dr. Westgard's complete presentation, as well as two Sigma-metrics Charts and instructions on how to use them in QC Design.
Westgard Sigma Analysis: A new direct HbA1c Method
At the 2008 AACC/ASCLS convention, a poster was presented for a new direct enzymatic assay for %HbA1c. How does it stack up against HPLC and immunoassay methods? How do you judge a method when you've got multiple comparison methods and multiple quality requirements?
Interview: Dr. R. Neill Carey (A brief introduction to EP 15)
We were fortunate to get R. Neill Carey, PhD, the chair of the CLSI EP 15 committee, to present and
explain that new standard at the Chicago Method Validation workshop. He also contributed a chapter to the new Basic Method Validation manual on the same topic. But for those who have never heard of EP 15 before, we conducted a short interview with Dr. Carey. This short introduction to EP 15 may pique your interest in this new guideline.
Thinking about Three Sigma: 2 thoughts on troublesome performance
In a previous lesson, we discussed some possible actions to take when the Sigma-metric for a method is higher than Six. But what about those methods with low Sigma-metrics? What do you do when Sigma analysis delivers bad news?
Posted by Sten Westgard
One of the highlights for me of the AACC convention in Washington, DC, was my inclusion in a poster that analyzed the method performance of the Abbott Architect c8000. I'm pictured here with fellow authors (left to right) Gene Osikowicz, Charles Wilson, and John Baker (lead author). They deserve most of the credit for the work of collecting the data.
The poster can be viewed here and the QC application on Westgard Web can be viewed here. -----
What's New this month at Westgard Web:
By Sten Westgard, MS
While Dr. Westgard has spoken about the "War of Words" between Uncertainty and Total Error in several essays (here, here and here most recently), we thought readers might want an additional perspective on the issue.
Dietmar Stockl, an expert in statistics and laboratory quality control from across the Atlantic, graces us with an guest essay on the calculation, use, benefits and limitations of measurement uncertainty: Time to Engage in Measurement Uncertainty. Dr. Stockl provides an in-depth look at uncertainty concepts and calculations, as well as a moderate viewpoint on the use of the term. He views both Total Error and Measurement Uncertainty are useful concepts and believes there is room in the world for both of them. It's not necessary for one term to eliminate the other.
Not so coincidentally, a colleague of Dr. Stockl's, Linda Thienpont, has a letter in Clinical Chemistry talking about the attempt to incorporate bias into the calculation of measurement uncertainty. If bias can be thrown into the uncertainty calculations, a case could be made that Total Error is no longer necessary. Dr. Thienpont points out that slipping bias into the uncertainty calculations is not a good idea and can lead to distorted results. She concludes that bias must remain separate from uncertainty calculations, which means another approach like Total Error is required to account for it.
See more at Thienpont LM. Calculation of measurement uncertainty-Why bias should be treated separately. Clin Chem 2008;54:1587 (subscription required) -----
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
Does this look like an error to you?
The latest ISO 15189 version has a new rule. Measurement Uncertainty is no longer optional, it's mandatory.
Do you know how to calculate MU?
Another chance to review instrument performance on the Siemens Vista. Back in 2012, we looked a study that assessed the method performance of cancer markers on the Vista. Now we've found a second study, this time one that compares method performance of the new Vista with the older Immulite methods.
Do two studies tell the same story?
Would your lab like to join a pilot project that monitors patient 50th percentiles? A project that would look across labs and manufacturers to develop a direct, real-time Quality Indicator that would fulfill ISO 15189's requirement for monitoring the quality of analysis of patient samples?
Looking for a few, good labs willing to share data
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Could your lab catch this error?
A recent letter to the Journal of Clinical Pathology showed an example of the consequences of missing a lab error for 10 days. Commendable that this laboratory was willing to share its challenges with the wider world. But it raises the question, how many labs could have caught this error? When we widen our limits with larger SDs and reduce our use of control rules, are we at risk of becoming blind to medically important errors?Does this look like an error to you?
From ISO, What's New? Labs must MU!
The latest ISO 15189 version has a new rule. Measurement Uncertainty is no longer optional, it's mandatory.
Do you know how to calculate MU?
Cancer markers on the Vista, Second look
Another chance to review instrument performance on the Siemens Vista. Back in 2012, we looked a study that assessed the method performance of cancer markers on the Vista. Now we've found a second study, this time one that compares method performance of the new Vista with the older Immulite methods.
Do two studies tell the same story?
Quality Kickstarter: Patient Percentile Monitoring
Would your lab like to join a pilot project that monitors patient 50th percentiles? A project that would look across labs and manufacturers to develop a direct, real-time Quality Indicator that would fulfill ISO 15189's requirement for monitoring the quality of analysis of patient samples?
Looking for a few, good labs willing to share data
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Posted by Sten Westgard, MS
See the latest articles on Westgard Web
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Posted by Sten Westgard, MS
Posted by Sten Westgard, MS