Measurement Uncertainty (MU) - Genetic Testing Lab - Lack of suitable CRM - ISO 17025

J

jane lai

#1
Our testing laboratory faces some problem dealing “Measurement Uncertainty” for application of ISO 17025 (genetic testing).

MU can be estimated using the value of within-laboratory reproducibility.
Using the repeated independent analyses of real samples.
Carry out bias control using reference materials.

However, we are lack of suitable Certified References Materials (CRMs) to calculate the bias of the method. Is there any suggestion? Thanks!:eek:
 
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Q

Qualqueen

#2
Re: Measurement uncertainty genetic testing lab

:bigwave: Jane,

I went to Wikipedia and found this definition of CRM:

Certified Reference Materials (CRMs) are ‘controls’ or standards used to check the quality and traceability of products. A reference standard for a unit of measurement is an artifact that embodies the quantity of interest in a way that ties its value to the reference base for calibration.

My understanding of this is that all you need is a set of standards (i.e. Gage Blocks - Grade 1) that has been calibrated by an accredited Laboratory (Preferrably an outside source) that is certified to 17025. With these gages, you then have a standard as to compare your actual measurements. :)
 
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harry

Super Moderator
#3
Re: Measurement uncertainty genetic testing lab

...............However, we are lack of suitable Certified References Materials (CRMs) to calculate the bias of the method. Is there any suggestion? Thanks!:eek:
I guess you are from Malaysia.

1. Approach your Chemistry Society for help and assistance. They may be able to refer you to people who can help - perhaps to participate in some kind of collaboration.
2. Check if any local universities can help you - they are usually better equipped.
 
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Z

zamclachia

#4
Re: Measurement uncertainty genetic testing lab

The simplest approach we are able to adopt is to determine SD(iR) – intermediate reproducibility (within-laboratory) and simply multiply by a coverage factor of 2. This should give you a good estimate of uncertainty at 95 % confidence.

For bias determination it is possible to spike samples (preferably blank or low concentration), make the assumption that the uncertainty of the spike is zero, and analyze six or more replicates, or alternatively duplicate (> 6 duplicates) analysis over a period of time under intermediate reproducible conditions (Same lab, same equipment, preferably different analysts and reagents).
 
J

jane lai

#5
Re: Measurement uncertainty genetic testing lab

Hi!

Our lab is dealing with genetic testing instead of chemical.

So far, I have search the CRMs through some suppliers but we can’t a suitable CRMs. The existing market still lack of CRMs for genetic testing.

Zamclachia: I have developed an experimental design for the “within-laboratory” reproducibly as you mentioned. For the bias determination, your suggestion sound reasonable to me.
Assume that the uncertainty of the spike is zero;
Prepare a range of matrix spike range from low, medium to higher concentrate of target analyte;
Determine the recovery of a matrix spike provides an indication of how efficient the analytical procedure.

Is it necessary to apply minimum of 6 replicates? Does anyone of you have any relevant journals or papers to recommend?
 

harry

Super Moderator
#6
Re: Measurement Uncertainty (MU) - Genetic Testing Lab - Lack of suitable CRM - ISO 1

Our lab is dealing with genetic testing instead of chemical.
I am aware but the Chemistry Society is where the chemist, lab people (registered chemist), university lecturers, professors and even deans congregate. Many of them are involved with bio-tech also. No guarantee but a better bet.
 
Z

zamclachia

#7
Re: Measurement uncertainty genetic testing lab

Hi!

Our lab is dealing with genetic testing instead of chemical.

So far, I have search the CRMs through some suppliers but we can’t a suitable CRMs. The existing market still lack of CRMs for genetic testing.

Zamclachia: I have developed an experimental design for the “within-laboratory” reproducibly as you mentioned. For the bias determination, your suggestion sound reasonable to me.
Assume that the uncertainty of the spike is zero;
Prepare a range of matrix spike range from low, medium to higher concentrate of target analyte;
Determine the recovery of a matrix spike provides an indication of how efficient the analytical procedure.

Is it necessary to apply minimum of 6 replicates? Does anyone of you have any relevant journals or papers to recommend?
[FONT=&quot]Let me have a look at what I can find re. 6 replicates. As a non statistician I believe that less than 6 sets of data become statistically problematic.[/FONT] I do have a research paper dealing with the use of SD(iR) * 2 to determine MU. If you want a copy, please drop me a mail as I am not sure re. copyright.
 
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