What is Measurement of Uncertainty?
Measurement Uncertainty (MU) relates to the margin of doubt that exists for the result of any measurement, as well as how significant the doubt is. For example, a piece of string may measure 20 cm plus or minus 1 cm, at the 95% confidence level. As a result, this could be written: 20 cm ±1 cm, with a confidence of 95%. Therefore, we are 95% sure that the piece of string is between 19 cm and 21 cm long.
Standards such as ISO 15189 require that the laboratory must determine uncertainty for each test. However, they have not specified how this should be done.
How do we calculate Measurement Uncertainty using QC data?
Employing your QC data to calculate uncertainty makes several assumptions; your test system is under control, the patient samples are treated in the same manner as your controls and gross outliers have been removed. If you choose to use your QC data to calculate this you should ensure that you use a commutable control with a matrix similar to that of a patient sample, with analytes present at clinically relevant levels
To calculate MU, labs must look at the intra-assay precision and inter-assay precision of their test.
Intra-assay precision: Sometimes known as ‘within run’ precision, is where 20 or more replicates of the same sample are run at the same time, under the same conditions (calculated from a single experiment). Intra-assay precision helps to assess systematic uncertainties
Inter-assay precision: Sometimes known as ‘between run’ precision, is where 20 or more replicates are run at different times – e.g. 1 replicate every day for 20 days (can be calculated from routine IQC data). Inter-assay precision can help identify random uncertainties within the test system.
*The Australian Association of Clinical Biochemists (AACB) recommends that at least 6 months’ worth of QC data are used when calculating the inter-assay precision1.
Once the data is collected, you must calculate the standard error of the mean (SEM) of the intra-assay precision (A) and the SD of the inter-assay precision (B) in order to measure the uncertainty (u). Once A and B have been calculated, they need to be squared, added together and the square root of the sum found:
As uncertainty is calculated as SD and 1SD is equal to 68% confidence on a standard Gaussian curve, we can conclude that if we multiply using a coverage factor of 2, we can attain 2SD confidence of 95%. This is known as the Expanded Uncertainty (U):
What is the Advantage of Measurement Uncertainty for a lab?
Labs need to carry out MU as it is a requirement of ISO 15189. It states: “The laboratory shall determine measurement uncertainty for each measurement procedure, in the examination phases used to report measured quantity values on patients’ samples. The laboratory shall define the performance requirements for the measurement uncertainty of each measurement procedure and regularly review estimates of measurement uncertainty”.
MU also helps determine whether the difference between two results is negligible due to uncertainty or significant due to a genuine change in condition of the patient; giving labs a greater confidence in reported results.
How can Randox help?
Our new Acusera 24.7 Live Online software provides automatic calculation of MU, saving valuable time and helping labs meet ISO 15189 requirements with ease.
Contact firstname.lastname@example.org to find out how your lab can benefit from Acusera 24.7 Live Online
Drive for more accurate results in your laboratory
We’ve all been there, you’re in the middle of a run of patient tests when you are alerted to an out of control event, such as your analyser is reporting QC results 25% low to target. What do you do? In reality, we all know that the problem is unlikely to correct itself, especially if it’s a calibration or analyser issue. Human error is a potential factor, however all possible causes must be eliminated to proceed with patient testing.
What’s the solution?
ISO 15189:2012 recommends that a laboratory should “have a procedure to prevent patient results in the event of a quality control failure”. Implementing an interlaboratory data management program which features peer group reporting can help you meet this requirement and monitor the results you are producing. Such programs can help detect errors in the analytical phase of patient testing, through the automatic application of pre-programmed QC rules, thus alerting staff to failed results.
Why must Peer Groups be a feature?
A peer group is defined as a “Community in which most or all members have roughly the same characteristics…” (Businessdictionary.com, accessed 2017). In this instance the characteristics could refer to the; instrument, test method or QC material in use. As such peer group programmes could help you detect errors in your laboratory by comparing your results to those who are employing a similar method, instrument and QC to what you are using, i.e. comparing apples for apples. Therefore it is essential that the peer group data you require is available in real-time, to ensure you are accessing the most up-to-date data when reviewing your patient test results.
Take the example from the introduction. You’re in the middle of a run of patient tests when you are alerted to an out of control event, such as your analyser is reporting QC results 25% low to target. As part of your troubleshooting procedures, you are able to compare your results to the results of your peer group and note that this is an isolated incident. Consequently, you have eliminated a widespread problem with the QC, reagent or calibrator and narrowed down the root cause to one of the components in your test system. Thus saving you time in the troubleshooting process.
Benefits of Peer Group Comparison
There are a number of benefits to employing peer group comparison in your laboratory. Peer group data comparisons facilitate faster troubleshooting, helping you identify whether the problem you are seeing is unique to your laboratory, or if other laboratories are reporting the same issue. If other laboratories are reporting the same issue it is possible to conclude that there is a widespread problem with either the QC, reagent or calibrator. On the other hand, if it is not occurring within your peer group you will have to investigate further, reviewing your QC processes. As a result, you could resolve issues much quicker by eliminating either a supplier or laboratory issue. Furthermore, you can also eliminate the need for unnecessary repeat tests or instrument maintenance, saving both valuable time and money.
Other characteristics you should look out for
Whilst peer group comparison is a useful feature there are a number of other features you should consider when selecting the right interlaboratory data management program for you. These include;
- Automatic calculation of Measurement Uncertainty, Total Error and Sigma Metrics
- Multiple laboratory management on a single platform
- Accessing data anytime, anywhere via PC, laptop or tablet via a web-based platform
- All data charts you may require to assess whether any bias or imprecision issues are present
- Ability to combine data for multiple QC lots, analytes and instruments on a single Levey-Jennings or Histogram chart
- Automated data import via a direct connection to your LIMS
What can Randox offer?
At Randox we are passionate about quality control and believe in producing high-quality material that can streamline procedures for laboratories of all sizes and budgets through our Randox Quality Control brand. Acusera 24.7 Live Online is just one aspect of our extensive laboratory portfolio that has been designed to help you produce results you can trust. With Acusera 24.7 Live Online you can drive for more accurate results by monitoring and interpreting QC data online, anytime, anywhere. With access to an impressive range of features, including the automatic calculation of Measurement Uncertainty, Total Error and Sigma Metrics, Acusera 24.7 will ensure analytical quality.
Reviewing QC data can be an extremely time consuming and costly process. With manual statistical calculation laboratories risk missing or ignoring significant trends in QC data which could potentially put patients at risk. So how does a laboratory combat this? Simple; participate in an interlaboratory data management program that provides a quick, effective, accurate and detailed analysis of QC results. The answer to this program is Acusera 24•7 Live Online.
Acusera 24•7 Live Online
With the launch of Acusera 24•7 Live Online version 2.0, QC data review is now faster and simpler than ever before. Our program aims to save the laboratory precious time and money by instantly flagging any QC failures, ultimately ensuring accurate test system performance.
Designed to complement and be used primarily with our Acusera range of true third party controls, Acusera 24•7 Live Online has two primary functions; 1) management and interpretation of IQC data and 2) rapid and effective troubleshooting of QC failures via access to instantly updated worldwide peer group statistics.
These two functions have one common goal – being an effective tool for evaluating laboratory performance. With the launch of version 2.0 the software boasts even more functionality than before, ensuring any laboratory employing Randox Quality Control coupled with Acusera 24•7 Live Online will see benefits from the get-go.
Why should you use Acusera 24•7 Live Online?
Using Acusera 24•7 to help speed up the review process in your laboratory can reap dividends. The program has been designed for this specific reason and the features are geared towards helping the laboratory review, interpret, and analyse QC data quickly, effectively and accurately. One such example of this is the unique dashboard function which instantly flags any alerted or rejected results from the past 7 days, significantly reducing the time spent analysing reports and charts whilst simultaneously allowing any corrective action to be taken immediately with minimum disruption to the lab’s output.
Previously, peer group statistics would have been updated every 24 hours with Acusera 24•7 Live Online version 1.6, however, with the new release, peer data is about to get a unique upgrade. Gone are the days when you will have to wait 24 hours to get updated stats – Acusera 24•7 Live Online now has the ability to generate peer data live in real-time, thereby enhancing the laboratory’s troubleshooting capabilities and allowing labs to compare their data with others around the globe. What’s more there is no deadline for submission of results meaning labs can get a true reflection of performance at any time. Ultimately, laboratories will be able to easily identify if an issue is unique to them or a widespread issue amongst their peers. Such information will allow them establish a root cause quicker and spend less time troubleshooting.
The capacity to generate interactive charts and comprehensive reports automatically is a feature included in Acusera 24•7 that will aid quick review of QC data. Reports can be generated for a user-defined date range and provide a wealth of information. Reports include statistical analysis, statistical metrics, measurement uncertainty, exception and audit trail reports. Reports coupled with Levey-Jennings, Histogram and Performance Summary charts enable rapid and stress-free performance monitoring. The ability to add multiple instruments, QC lots and analytes to a single chart allows for comparative performance assessment and immediate identification of any trends.
We must not forget that Acusera 24•7 Live Online has already had a modernisation in the past few months. In November 2016 we announced the automatic calculation of Measurement of Uncertainty, Total Error and Sigma Metrics. These new features are also included in the version 2.0 launch of our Live Online program.
Our software is highly flexible with custom configurations of performance limits, multi-rules and target values designed to meet and exceed every laboratory’s needs.
With the ability to identify trends, system errors, minimise false rejections and bridge the gap between IQC and EQA, there really is no reason to look elsewhere for your analytical performance of QC.
For more information on Acusera 24•7 Live Online or our Acusera third party controls, click here.