The Westgard Rules

What's New on Westgard Web: February 2012

Posted by Sten Westgard, MS

UNCERTAINTY: IT'S OFFICIAL

CLSI has issued its C51A document, which officially brings the ISO
metrology concepts of uncertainty to the US. Dr. Westgard explores the
document in detail, explaining how uncertainty will impact the
laboratory.

ISO uncertainty: not just for metrologists anymore
 http://www.westgard.com/clsi-c51.htm

SIGMA-METRIC PILOT STUDY IN INDIA

A 2011 study from the Indian Journal of Clinical Biochemistry examined
the performance of a clinical chemistry instrument. We review the data
and provide graphic charts.

Do instruments perform differently in India?
 http://www.westgard.com/india-lab-sigma.htm

IS THERE A NEED FOR A MEAN RULE? QC DESIGN FOR A PHOSPHORUS METHOD

One question we get frequently is, "Do the violation of the 10x rule
mean anything for test X?" At the heart of this question is another
question: what QC rules are actually necessary to assure the quality of
a method? With the help of user-submitted data, we take a closer look
at this question.

What's the meaning of a mean rule violation?
 http://www.westgard.com/need-mean-rule.htm

Related Q&A on the blog: Are mean rules mandatory?
 http://james.westgard.com/the_westgard_rules/2012/02/mean-rule-can-iso-be-wrong.html

MORE QUALITY REQUIREMENTS: MINIMUM SPECIFICATIONS FOR ALLOWABLE TOTAL
ERROR

Last month, we had the privilege of publishing the latest database on
within-subject biologic variation in analytes, from the Ricos et al
group. In previous years, we have only posted the desirable
specifications. This year we are expanding to show the whole set: not
only desirable specifications but also optimal and minimum
specifications. How good should we be? How low can we go? These new
tables help provide some guidance.

Optimal specifications for allowable total error
 http://www.westgard.com/optimal-biodatabase1htm.htm

Minimum specifications for allowable total error
 http://www.westgard.com/minimum-biodatabase1.htm

Q & A on ISO and QC: Are Mean Rules Mandatory?

Posted by Sten Westgard, MS

Recently, a user submitted a question about the mandatory use of the 10_x rule on chemistry analytes as mandated by ISO 15189 through NABL:

"Specific criteria of accreditation of NABL India (for ISO 15189) say that 10x should be considered as a violation for clinical chemistry  and Immunoassay parameters. However we understand that Westgard rules consider it as a warning only. Please advise."

So, the central question is, does ISO 15189 mandate the use of the 10_x control rule?

Q & A: What happens when the SD is Zero?

Posted by Sten Westgard, MS

Here's a user-submitted quandry: how do you draw control limits for your method if you standard deviation is zero and your coefficient of variation is zero?

Here's the "proof" that this scenario actually happens:

As you see for line 006, the SD and CV for BUN is 0.0

So what's the problem, and what's a laboratory to do?

Pop Quiz: What does healthcare think of Risk Analysis?

Posted by Sten Westgard, MS

So we all know that Risk Analysis is coming to laboratories in the US. (click here if this is news to you). But Risk Analysis, particularly the FMEA technique (Failure Mode and Effects Analysis), is not new to healthcare. Outside the laboratory, plenty of healthcare practitioners have been performing FMEA.

So what do they think about this technique? Try and guess which one of these responses is from a someone in healthcare:

• "The jury's still out on the FMEA process because... has anybody evaluated FMEA as a tool for analysing risk? And it turns out there isn't... well why are we doing this process?... When all it is doing is bringing a few things to the surface, which is no bad thing, but it's not a validated process."
• "...Forget FMEA. It doesn't really work effectively, I don't think, and the scores are a hindrance rather than anything else, year... We wasted a lot of time on FMEA before we realized, this isn't actually working. Yeah, because I think you can get caught up on just the score, that's the thing."
• "The scoring in the FMEA teams need to be the same people, if you change half way through because of the highly subjective interpretation things change dramatically."