Posted by Sten Westgard, MS
Here's a question that came in about setting the control limits (or range) for a test:
"for some assays we're using this formula: actual SD * 3 and then divided by 2 plus or minus the mean is this acceptable or not because when we use that give us abit wider range than using the mean plus minus 2SD."
When we asked for an example, we got this data:
Manufacturer Data: SD = 22.5, Mean = 224
Actual Data: SD = 8.79, Mean = 223
"We're multiplying ourSD (8.79) by 3 and then we divide it by 2 to give us the new SD which is 13 (8.79*3/2 = 13).
Then we multiply this new SD 13 by 2 to give us the real 2 SD range which is 26.
So our range is now 197 - 249.
Are we following the right way or not?"
The answer, after the jump...
-----
From Dr. Carmen Ricos, on behalf o the SEQC-Analytical Quality Commission:
Posted by Sten Westgard, MS
Posted by Sten Westgard, MLO
In the November 2012 MLO magazine there is an intriguing article by Roy Midyett, a hematology supervisor, titled "Empty QC"
Here's how Mr. Midyett defines "Empty QC":
"Empty QC is any nominal QC that does not give techs performing the test any more confidence than they would have without the QC, and has by logic or experience, no influence on the reporting of the test."
Is Mr. Midyett correct? Have our QC procedures become meaningless gestures? More after the jump.
-----
Posted by Sten Westgard, MS
So here's a Normalized Method Decision chart for a cholesterol method.
Which method would you choose?
Posted by Sten Westgard, MS
Here's a range of statistics describing the performance of a glucose method. Try to pick: Which one has acceptable performance?
- method with combined uncertainty 3.69%
- method with combined uncertainty 6.79%
- method with expanded uncertainty 7.38%
- method with expanded uncertainty 13.58%
- method with 3.78 Sigma
Which method would you pick?
-----
Posted by Sten Westgard, MS
In the recent issue of Clinical Chemistry, an editorial reviews the current state of Vitamin D testing: "There is common agreement that 25-OHD is a 'difficult' analyte."
25-Hydroxyvitamin D: A Difficult Analyte, Graham D. Carter, Clin Chem 58:3; 486-488 (2012).
At the same time, the editorial notes that marked process is being made:
"Nevertheless, results submitted to the international Vitamin D External Quality Assessment (DEQAS) have shown a gradual reduction in interlaboratory imprecision (CV) in recent years - from >30% in 1995 to 15% in 2011."
The question is, is that reduction in imprecision good enough? Or is the quality required by Vitamin D still too "difficult"?
More after the jump...
-----
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
At the AACC/ASCLS conference in San Diego, many of the Sigma VP laboratories contributed to a poster on evaluating the applicability of various analytical performance specifications for AST:
Multisite study of AST analytical performance reveals disparities in global performance specifications
The full poster can be downloaded from our westgard.com download section here. (free membership required)
But what was most rewarding was meeting with many of the co-authors who came to the meeting.
Ms Ginny Foo, Mr. Rajkumar Rengaraju, Co-authors from Innovative Diagnostics, Singapore
more pictures after the jump
-----
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
Posted by Sten Westgard, MS
An interesting abstract was published at the Paris IFCC meeting. It detailed the EQA performance of a set of 12 public laboratories in Catalonia. Can you guess what the failure rate for these labs for biochemistry EQA?
- 14.5%
- 14%
- 3%
- none of the above
The answer, after the jump...
-----