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
The RX series analysers ensure that the on-board testing process is precise through many stages and therefore lead to accurate results in the laboratory. Our automated analysers go through an extensive washing system for cuvettes and includes acid, alkali and pure water wash steps. Liquid level sensor, crash, bubble and clot detection ensure that after the washing process is complete, whatever residue remaining has been completely removed from the cuvettes so that they are ready to be used again.
Randox understand the demands of the clinical chemistry laboratory and recognise the importance of maintaining a consistent workflow of high quality results. We pride ourselves in excellence of service. Through our global network, our team of trained engineers provide local service and support. There are 3 levels of service maintenance provisions to ensure a package to suit all laboratories; bronze, silver and gold packages.
Randox also offers technical support 24 hours a day, 7 days a week via a free electronic service called Powerline; this service provides customers with instant access to instructions for use (IFU), and instrument specific application (ISA) documents for a comprehensive list of instruments. Each RX series analyser requires minimal maintenance, as little as 5 minutes daily, and between 1 and 2 yearly preventative maintenance checks depending on the workflow of the analyser.
70% of medical decisions are based on laboratory results, therefore it is imperative that accurate results are produced in the laboratory. These test results lead to key decisions for the treatment of patients, therefore it is essential for an accurate diagnosis of all patient samples. A misdiagnosis can be life threatening, or lead to incorrect treatment plans delaying the recovery of the patient, which in turn can lead to high compensation costs for Hospitals and Laboratories for the affected patients.
The RX series analysers ensure accurate test results with a stringent validation process of all Randox Reagents. The QC functionality provides automatic flagging of inaccurate results and testing errors therefore helping laboratories identify and resolve issues quickly, minimising the possibility of misdiagnosis.
Precision, reliability and accuracy are hugely important within a laboratory. The RX series analysers offer these in abundance. Randox can provide consolidation of testing with validated reagents and cost effective Quality Controls, ensuring that your laboratories testing results are precise, reliable and accurate.
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