Measurement Uncertainty Vs Total Error
In a recent article, Error Methods Are More Practical, But Uncertainty Methods May Still Be Preferred, James Westgard comments on the latest developments in the debate on the use of analytical total error (TE) and measurement uncertainty (MU), a debate which has been regularly revisited for the last twenty years. This blog aims to briefly explore the benefits of MU and TE and attempt to draw a conclusion on which is most beneficial in the clinical laboratory.
Many things can undermine a measurement. Measurements are never made under perfect conditions and in a laboratory, errors and uncertainties can come from (Good Practice Guide No. 11, 2012):
- The measuring instrument – instruments can suffer from errors including bias, changes due to ageing, wear, poor readability, and noise.
- The item being measured – the sample may be unstable.
- The measurement process – the analyte may be difficult to measure
- ‘Imported’ uncertainties – calibration of the instrument.
- User error – skill and judgement of the operator can affect the accuracy of a measurement.
- Sampling issues – the measurements you make must be properly representative of the process you are trying to assess. I.e. not using fully commutable controls will mean your quality control process is not reflective of a true patient sample.
Random and systematic errors
The effects that give rise to uncertainty in a measurement can be either random or systematic, below are some examples of these in a laboratory.
- Random – bubbles in reagent, temperature fluctuation, poor operator technique.
- Systematic – sample handling, reagent change, instrument calibration (bias), inappropriate method.
Total Error (TE) or Total Analytical Error (TAE) represents the overall error in a test result that is attributed to imprecision (%CV) and inaccuracy (%Bias), it is the combination of both random and systematic errors. The concept of error assumes that the difference between the measured result and the ‘true value’, or reference quantity value, can be calculated (Oosterhuis et al., 2017).
TE is calculated using the below formula:
TE = %BIAS + (1.96 * %CV)
Measurement Uncertainty is the margin of uncertainty, or doubt, that exists about the result of any measurement.
There is always margin of doubt associated with any measurement as well as the confidence in that doubt, which states how sure we are that the ‘true value’ is within that margin. Both the significance, or interval, and the confidence level are needed to quantify an uncertainty.
For example, a piece of string may measure 20 cm plus or minus 1 cm with a 95% confidence level, so we are 95% sure that the piece of string is between 19 cm and 21 cm in length (Good Practice Guide No. 11, 2012).
Standards such as ISO 15189 require that laboratories must determine uncertainty for each test. Measurement Uncertainty is specifically mentioned in section 126.96.36.199:
“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.”
Uncertainty is calculated using the below formula:
u = √A2+B2
U = 2 x u
A = SD of the Intra-assay precision
B = SD of the Inter-assay precision
u = Standard Uncertainty
U = Uncertainty of Measurement
Error methods, compared with uncertainty methods, offer simpler, more intuitive and practical procedures for calculating measurement uncertainty and conducting quality assurance in laboratory medicine (Oosterhuis et al., 2018).
It is important not to confuse the terms ‘error’ and ‘uncertainty’.
- Error is the difference between the measured value and the ‘true value’.
- Uncertainty is a quantification of the doubt about the measurement result.
Whenever possible we try to correct for any known errors: for example, by applying corrections from calibration certificates. But any error whose value we do not know is a source of uncertainty (Good Practice Guide No. 11, 2012).
While Total Error methods are firmly rooted in laboratory medicine, a transition to the Measurement Uncertainty methods has taken place in other fields of metrology. TE methods are commonly intertwined with quality assurance, analytical performance specifications and Six Sigma methods. However, Total Error and Measurement Uncertainty are different but very closely related and can be complementary when evaluating measurement data.
Whether you prefer Measurement Uncertainty, Total Error, or believe that they should be used together, Randox can help. Our interlaboratory QC data management software, Acusera 24•7, automatically calculates both Total Error and Measurement Uncertainty. This makes it easier for you to meet the requirements of ISO:15189 and other regulatory bodies.
This is an example of the type of report generated by the 247 software. MU is displayed for each test and each lot of control in use therefore eliminating the need for manual calculation and multiple spreadsheets.
Fig. A and Fig. B above are examples of report generated by the 24•7 software. Fig.A shows how MU is displayed for each test and each lot of control in use therefore eliminating the need for manual calculation and multiple spreadsheets. Fig. B shows TE displayed for each test.
Good Practice Guide No. 11. (2012). Retrieved from http://publications.npl.co.uk/npl_web/pdf/mgpg11.pdf
Hill, E. (2017). Improving Laboratory Performance Through Quality Control.
Oosterhuis, W., Bayat, H., Armbruster, D., Coskun, A., Freeman, K., & Kallner, A. et al. (2017). The use of error and uncertainty methods in the medical laboratory. Clinical Chemistry and Laboratory Medicine (CCLM), 56(2). http://dx.doi.org/10.1515/cclm-2017-0341
Westgard, J. (2018). Error Methods Are More Practical, But Uncertainty Methods May Still Be Preferred. Clinical Chemistry, 64(4), 636-638. http://dx.doi.org/10.1373/clinchem.2017.284406
Medical Laboratory Professionals Week is taking place this year from 22nd– 28th April 2018. This is an annual celebration of professionals working in the laboratory, highlighting and recognising their contributions to medicine and healthcare.
To celebrate Medical Laboratory Professionals Week the RX series interviewed Aidan Murphy, one of our laboratory analysts at Randox to find out more about what his job in the lab entails day-to-day. Aidan works with the RX series of clinical chemistry analysers and Randox QC on a daily basis.
We asked Aidan a few questions about his life as a scientist. See what he gets up to in Randox on a daily basis …
1. What attracted you to a career in laboratory science?
Science has always interested me in both my academic and personal life, I always aspired to get a science based degree and after achieving this I now hope to improve my laboratory skills to increase my employability.
2. What were your stronger subjects at school?
My strongest subjects in school were biology, chemistry, music and politics. Some of which are more applicable to my current role than others.
3. What does your job in Randox entail?
My job entails a variety of roles ranging from testing Randox diagnostic kits before they’re released to customers as well as maintenance and precision checks of the machines in our lab.
4. What aspects of your job do you enjoy the most?
The independence in my job is great. Knowing what I have to do at the start of each week and the deadlines to do these jobs requires me to organise and prioritise my work accordingly.
5. What are some common preconceived ideas the public have about what laboratory staff do?
From my friends’ ideas of what I do in the lab I have found that a stereotypical image of a lab is one of a dark quiet lab full of strange equipment and even stranger people. However fortunately my lab is a lively one and thankfully with normal people.
6. In your opinion, what are the most important aspects of laboratory work?
Following correct protocols and procedures are imperative in an efficient laboratory. As well as this, good lab practice and good hygiene can have a massive effect on the accuracy of our results.
7. What’s in your lab coat pocket?
My lab coat pockets are quite boring. I have a pair of safety goggles, some post-its and some pens and markers.
8. In what ways does your work make a difference to people’s lives?
Randox is dedicated to improving the quality of diagnostics globally, so knowing that the kits that I have tested are then sent to customers to be used in patient diagnosis gives me a level of job satisfaction that I haven’t got from previous jobs.
Aidan is a fundamental member of the Randox team and plays an essential role in the diagnosis and prevention of disease through his work. Without our valuable laboratory team working extremely hard behind the scenes the lifesaving work we do here at Randox would not be possible.
To find out more about Randox products contact us at theRXseries@randox.com.
Check out our social media sites for more on Medical Laboratory Professionals Week.
Laboratory accreditation provides formal recognition to competent laboratories, providing a means for customers to identify and select reliable services (CALA, n.d.). Use of accreditation standards by clinical laboratories enables them to drive gains in quality, customer satisfaction, and financial performance. This is essential at a time when laboratory budgets are shrinking.
Some key benefits include:
- Recognition of testing competence – as mentioned above, customers can recognise the competence of a lab with an internationally recognised standard.
- Marketing advantage – accreditation can be an effective marketing tool as labs can demonstrate their quality and overall competence.
- Benchmark for performance – laboratories can determine whether they are performing to the appropriate standards and provides them with a benchmark to maintain that standard.
To maintain the global recognition gained from accreditation, labs are evaluated regularly by an accreditation body to ensure their continued compliance with requirements, and to check that standards are being maintained. (CALA, n.d.).
In a comprehensive study conducted by Rohr et al. (2016) it was found that, while accounting for as little as 2% of total healthcare expenditure, in vitro diagnostics (IVD) account for 66% (two thirds) of clinical decisions. Despite such a small percentage of budget dedicated to it, IVD plays a huge role in patient care so it is vital that there is guidance in place to ensure quality standards are met. Poor performance of tests at any stage of care and treatment can reduce the effectiveness of treatment and deny appropriate care to patients in need (Peter et al., 2010).
ISO 15189 is an international accreditation standard that specifies the quality management system requirements particular to medical laboratories and exists to encourage interlaboratory standardisation, it is recognised globally.
Meeting ISO Requirements
Scroll through below to learn how ISO 15189 regulates aspects of a clinical laboratory and how Randox can help you meet these suggestions.
Review of QC data
“The laboratory shall have a procedure to prevent the release of patient results in the event of quality control failure. When the QC rules are violated and indicate that examination results are likely to contain clinically significant errors, the results shall be rejected…QC data shall be reviewed at regular intervals to detect trends in examination performance”
– ISO 15189:2012
Acusera 24∙7 will automatically apply QC multi-rules, alert you to or reject any results that violate the QC multi-rules or performance limits, generate a variety of charts allowing visual identification of trends and provide access to real-time peer group data to assist with the troubleshooting process.
Calculation of MU
“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.”
– ISO 15189:2012
Acusera 24∙7 is the only QC data management platform that incorporates the automatic calculation of Measurement Uncertainty (MU) as well as other performance metrics, including Total Error.
“The laboratory shall use quality control materials that react to the examining system in a manner as close as possible to patient samples”
– ISO 15189:2012
Acusera True Third Party Controls are fully commutable, behaving like a real patient sample, reducing the need to re-assign QC target values when the reagent batch is changed, reducing labour and costs.
Medical decision levels
“The laboratory should choose concentrations of control materials, wherever possible, especially at or near clinical decision values, which ensure the validity of decisions made”
– ISO 15189:2012
Acusera True Third Party Controls are designed to challenge instruments across the entire clinical reporting range.
Comparison of results across instruments
“Laboratories with two or more analysers for examinations, should have a defined mechanism for comparison of results across analysers”
– ISO 15189:2012
Acusera 24∙7 is capable of combining multiple data sets on a single Levey-Jennings, Histogram of Performance Summary chart, enabling at-a-glance performance review and comparative performance assessment. A unique multi-instrument report is also available via our RIQAS EQA programme allowing performance of each instrument to be compared.
Third Party Control
“Use of independent third party control materials should be considered, either instead of, or in addition to, any control materials supplied by the reagent or instrument manufacturer”
– ISO 15189:2012
Acusera True Third Party Controls are manufactured completely independently of and calibrators and assigned values through a pool of instruments across the world, making them true third party controls.
At a conference in Belgium in 2016, data, which highlighted the most common areas of non-conformance in laboratories, showed that nonconformities were most prevalent in sections 5.5 and 5.6 of ISO 15189. This data is visualised in fig. A below. Furthermore, a study by Munene et al. (2017) has had similar findings, as visualised in fig. B. The greatest number of nonconformities occur in the sections that are concerned with insufficient assay validation and quality of examination procedures. These studies specifically identified the lack of independent controls, QC not at clinically relevant levels, commutability issues, and a lack of interlaboratory comparison as major issues.
Randox Quality Control products are designed to target these areas, making it easier to conform to ISO 15189 standards.
CALA. The Advantages of Being an Accredited Laboratory. Canadian Association for Laboratory Accreditation. Retrieved from http://www.cala.ca/ilac_the_advantages_of_being.pdf
Munene, S., Songok, J., Munene, D., & Carter, J. (2017). Implementing a regional integrated laboratory proficiency testing scheme for peripheral health facilities in East Africa. Biochemia Medica, 110-113. http://dx.doi.org/10.11613/bm.2017.014
Peter, T., Rotz, P., Blair, D., Khine, A., Freeman, R., & Murtagh, M. (2010). Impact of Laboratory Accreditation on Patient Care and the Health System. American Journal Of Clinical Pathology, 134(4), 550-555. http://dx.doi.org/10.1309/ajcph1skq1hnwghf
Rohr, U., Binder, C., Dieterle, T., Giusti, F., Messina, C., & Toerien, E. et al. (2016). The Value of In Vitro Diagnostic Testing in Medical Practice: A Status Report. PLOS ONE, 11(3), e0149856. http://dx.doi.org/10.1371/journal.pone.0149856
Benefits of High-Sensitivity Troponin I (hs-TnI)
Chest pain is a common symptom; 20% to 40% of the population will experience chest pain during their lifetime. There are many causes of chest pain, some of which are benign, while others are potentially life threatening. Importantly, in patients with chest pain caused by an acute coronary syndrome (ACS) or angina, there are effective treatments to improve symptoms and prolong life, emphasising the importance of early diagnosis in patients where chest pain may be of cardiac origin (Skinner et al, 2010). Chest pain is one of the most common reasons for emergency admission to hospital and is a heavy burden on health-care resources. A strategy to identify low-risk patients suitable for immediate discharge would have major benefits (Shah et al., 2015).
The introduction of high-sensitivity troponin I (hs-TnI) allowed clinical practitioners in the UK to implement a novel and radically different chest pain pathway. The new pathway uses an admission hs-TnI of <1.9ng/L to discharge patients with suspected acute coronary syndrome (ACS).
The percentage of chest pain patients admitted to the hospital declined from 60.9% to 38.4% and the mean length of stay reduced from 23 hours 2 minutes to 9 hours 36 minutes. (Ford, 2017)
What it means
The adoption of high-sensitivity Troponin I (hsTnI) has allowed RWT to relieve pressure on their emergency department by discharging patients with a hs-TnI level below 1.9ng/L, the limit of detection for the assay.[/mpc_icon_column]
Accurate test results are vitally important in diagnosis of chest pain and effective quality control is crucial to achieving this. The Randox Liquid Cardiac Control Level 1 features ultra-low levels of Troponin I, enabling it to challenge the sensitivity of analysers, ensuring confidence in vital clinical decisions.
Features & Benefits
Liquid ready-to-use – enables ultimate ease-of-use, saving time and money. Suitable for both clinical laboratories and point-of-care testing (POCT), where important clinical decisions are made.
100% human serum – ensures complete commutability whereby the control mimics a real human sample, reducing annoying shifts with a change in reagent batch.
Consolidation – comprising an impressive 8 cardiac markers, featuring ultra-low levels of Troponin I meaning a separate high-sensitivity control is not required.
Open vial stability of 20 days at 2°C – 8°C for all analytes – enables less wastage, saving money.
Ford, C. (2017). Benefits of High Sensitivity Cardiac Troponin I at Admission. Clinical Laboratory Management Association, (July/August 2017), 22-24.
Shah, A., Anand, A., Sandoval, Y., Lee, K., Smith, S., & Adamson, P. et al. (2015). High-sensitivity cardiac troponin I at presentation in patients with suspected acute coronary syndrome: a cohort study. The Lancet, 386(10012), 2481-2488. http://dx.doi.org/10.1016/s0140-6736(15)00391-8
Skinner, J., Smeeth, L., Kendall, J., Adams, P., & Timmis, A. (2010). NICE guidance. Chest pain of recent onset: assessment and diagnosis of recent onset chest pain or discomfort of suspected cardiac origin. Heart, 96(12), 974-978. http://dx.doi.org/10.1136/hrt.2009.190066
This British Science Week 2018, Randox Quality Control are celebrating the hard work our team puts in every day, to help bring the best Quality Control products to the market.
We caught up with Edward Hill, QC Product Specialist, to explain a bit about what his role involves and how Randox QC are impacting on global healthcare!
What is your position and what does it involve?
I am a QC Product Specialist at Randox Laboratories. This is a hugely varied role, and some of my general duties involve; creating educational material for laboratory professionals, conducting competitor comparisons to ensure we are always one step ahead of the competition, staying up-to-date with the latest industry trends and thinking of new and innovative ways to interact with our customer-base.
For those of us who aren’t in the industry, can you give us a brief snapshot of what Quality Control is and why we use it?
When a patient has their blood/urine/serum etc. taken, it must be sent to the laboratory for analysis. Laboratory professionals run the patient sample on a clinical instrument, which gives a quantitative result for each analyte. However, the laboratory professional does not know whether the value given by the instrument is correct or not. For this reason, the laboratory professional must use a Quality Control – which is a material designed to mimic the patient sample, and has a known concentration of each analyte.
When the laboratory professional runs the QC material on their instrument, they can compare the obtained result with the expected result. If these values are comparable, then the laboratory professional can be confident that their instrument is reporting accurately. Essentially, QC is a ‘practice run’ to ensure the testing system is working correctly.
How does your teams’ work impact on global healthcare?
Quality Control is a hugely important part of laboratory quality. Around 70% of clinical decisions are made based on laboratory results, so it is plain to see how significant Quality Control practices can be in relation to global health care. My work, as well as the work of the wider Quality Control team, is focused on making end-users aware of the importance of Quality Control. We aim to provide advice and recommendations to optimise accuracy and efficiency.
As a company, Randox prioritizes quality above all else, and this ethos is perfectly reflected by the Quality Control team. We work tirelessly to provide quality products and simplify the entire testing process – giving the laboratory professionals more time to do what they do best; provide accurate results time and time again.
What is your favourite Randox QC product and why?
My favourite QC product is the Acusera Liquid Cardiac Control. It’s my favourite control because it perfectly displays all the advantages of Acusera in a single product:
- Highly consolidated analyte list without any unnecessary extras, keeping costs low
- True third party
- Manufactured with 100% human serum, giving full commutability
- Liquid ready-to-use and suitable for POC testing
- Clinically relevant ranges, with ultra-low levels of Troponin I
- Long open vial stability of 30 days
Competitors often offer additional low level Troponin I controls. The thing I like most about the Acusera Liquid Cardiac Control is that the Troponin I levels are still lower than the ‘ultra-low level’ competitor controls – showing that Acusera gets it right the first time, rather than supplementing weak QC products with additional products at an extra cost.
Approximately 70% of clinical decisions are based on laboratory test results. Poor laboratory quality can result in unreliable test results ultimately leading to misdiagnosis, inappropriate treatment and may even impact the overall quality of life for the patient. Having multiple instruments can often add to the difficulties faced in labs. The importance of quality medical services is recognised globally with several bodies existing internationally including ISO (International Organisation for Standardisation) who have developed a set of guidelines and quality systems to ensure reliable test results – ISO 15189:2012.
About ISO 15189:2012
ISO 15189:2012 was designed to outline the “requirements for competence and quality that are particular to medical laboratories”. Laboratory competence and quality are critical in patient diagnosis and care to ensure they meet the need of the clinicians & patients. Gaining accreditation to ISO 15189:2012 will assure clinicians employing your services that they will be benefitting from accurate results which have been measured against a consistent standard. You could benefit too from cost savings and enhanced end-user satisfaction.
ISO 15189:2012 divides the quality requirements of the laboratory into two distinct areas; Internal Quality Control (IQC) and External Quality Assessment (EQA). By combining both you can comprehensively review and monitor the overall performance of your laboratory, including personnel, equipment, and procedures.
A particular requirement of ISO 15189:2012 is:
“Laboratories accredited according to ISO 15189 that have two or more analysers for examinations, should have a defined mechanism for comparison of results across analysers”
How Randox can help labs with multiple instruments?
Randox offers solutions in both IQC and EQA to help your lab meet the ISO 15189 requirements.
Our international EQA scheme is the largest in the world with 45,000 participants in 133 countries.
All RIQAS participants can register up to five separate instruments per programme at no extra cost. Individual reports for each instrument plus a unique multi-instrument report are provided. The multi-instrument report plots the performance of each individual instrument on a single, colour coded Levey-Jennings chart, ensuring instant identification of any differences in instrument performance. Additional sample packs may be ordered as required.
The multi-instrument report includes many of the same statistical features found in the main RIQAS report including; CV%, SDI, RMSDI, %DEV, RM%DEV, Target Score, and RM Target Score.
Our stress free QC analysis software is designed to assist in the management of daily QC activities.
Support for multiple instruments
Acusera 24.7 Live Online allows laboratories to conveniently combine multiple instruments as well as analytes and QC lots on a single Levey-Jennings chart, allowing comparative performance assessment and immediate visualisation of any ongoing or emerging trends.
Helping you get accredited
Randox helps you get accredited by offering products from the full spectrum of Quality Control, meaning you never have to look elsewhere. Not all manufactures can offer these features.
To find out more about how we can help you meet ISO 15189 requirements, contact us using the form below.
Some laboratory professionals believe that using Internal Quality Control (IQC) and External Quality Assurance (EQA, also known as Proficiency Testing) material from the same provider can lead to increased levels of qc bias, or that their test system will not be appropriately challenged. It is important to address these concerns, because some labs may in fact be hindering their own performance by using IQC and EQA material from different sources.
It is important to first understand how IQC and EQA work together to help form a complete Laboratory Quality Management System.
IQC and EQA in Laboratory Quality Management
IQC is a means of monitoring test system precision on a daily basis. IQC effectively evaluates test system performance over time, so that any sudden or gradual shifts in performance can be detected. However, while IQC is an effective performance monitor, it cannot detect more intricate problems like calibration errors or wide acceptable limits provided by some QC manufacturers.
EQA is essential for challenging test system accuracy, and is carried out less frequently than IQC testing. EQA samples are tested ‘blind’ and the results are returned to the scheme organiser. As EQA testing compares an individual lab’s performance to other labs using the same method and instrument, it is a very effective tool for identification of potential issues.
Is there any disadvantage to using IQC and EQA material from the same provider?
The answer to this question depends primarily on the source material of the IQC and EQA. If an IQC provider manufactures their material using artificial additives or components of animal origin, then it will not be suitable to use EQA material from the same provider. Westgard (2011) maintains that using non-commutable IQC or EQA material can lead to results becoming compromised due to matrix effects – something which would not happen using commutable controls.
For example, with Immunoassay testing, non-human components of IQC material interact with antibodies in the reagent in a different way to fully human patient samples – ultimately giving unpredictable shifts, and not adhering to the ISO 15189 requirement to: “use quality control materials that react to the examining system in a manner as close as possible to patient samples”.
However, if the IQC and EQA material is manufactured using a source material which is similar in composition to patient samples (100% human), this commutable control will adequately mimic patient sample performance; meaning labs can use EQA and IQC material from the same provider with confidence that the integrity of their results is maintained.
ISO 15189 also states: “Use of independent third party control materials should be considered…”. In this instance, ‘Independent’ does not mean from a separate provider. It means that the QC material should not be optimized for use on one specific instrument (i.e. not dependent on a single instrument/method type).
No regulatory body states a requirement to use different providers for IQC and EQA material. Indeed, using IQC from one provider and EQA from another provider could increase the risk of labs using non-commutable material.
Labs should use commutable IQC and EQA material for a true assessment of their test system. Randox QC and RIQAS EQA are specifically designed with commutability in mind, giving labs a control which reflects patient sample performance and ensures excellent performance.
How can we help?
To learn how Randox can offer a complete solution for your laboratory, follow the links below or submit a question using the form above.
Westgard, S. (2011). Is QC Quality Compromised?. Available: https://www.westgard.com/qc-quality-compromised.htm. Last accessed 31st October 2017.
Got a question?
Quality Control (QC) is vital for the clinical laboratory in order to ensure the accuracy and precision of patient test results. Without a robust QC strategy, test system errors could go undetected, potentially resulting in misdiagnosis and inappropriate/delayed patient treatment.
What are IQC and EQA?
IQC is used in the daily monitoring of test system precision and reproducibility. IQC essentially compares the internal laboratory’s performance over time, highlighting any deviations from ‘normal’ performance. While IQC is a good method of testing performance, it is not always robust enough to detect calibration errors or issues associated with ‘wide’ acceptable limits.
In an External Quality Assessment (also known as Proficiency Testing, or PT) program the EQA provider will deliver ‘blind’ samples to all EQA participants. The use of such ‘blind’ samples ensures EQA can be used to measure a laboratory’s bias and accuracy. These samples are analysed by the lab and results are returned to the EQA provider for analysis. The data are examined, means and SDs are calculated, and any outliers are highlighted. Reports are then generated and delivered to each participant, giving a summary of performance in comparison to the rest of the participant group.
Why Should Laboratories Carry out EQA Testing?
The World Health Organisation (WHO) recommends that a robust QA program should be implemented in any lab which carries out HIV testing, and Internal and External quality control should be carried out on an ongoing basis1.
Participating in a rigorous and robust EQA scheme is a requirement of ISO 15189. All labs seeking ISO 15189 accreditation need to be part of an EQA scheme which appropriately challenges their test system.
The Cost of Poor Quality EQA
The most common method of HIV detection is to utilise Enzyme Immunoassay (EIA) antibody testing2. EIA tests are highly sensitive and can be optimised for automation, facilitating high-volume testing. However, with higher volumes of testing comes a higher probability of error. With EIA assays, the most common error encountered is false positive results2.
False positive results have a number of implications. Any screen-positive results must be verified using a confirmatory test; usually a Western Blot assay. The Western Blot is much more labour intensive and expensive than EIA tests, and is not efficient enough for high volume testing2. Therefore, if a laboratory is producing a higher than average number of false positive results due to poor quality assurance practices, they will ultimately spend significantly more time and money on confirmatory tests.
How can EQA Improve HIV Testing Accuracy?
The main use of EQA is to verify the accuracy of laboratory testing. Accuracy refers to the closeness of the obtained result to the ‘true’ value. As EQA is tested using ‘blind’ samples, operator bias is eliminated and the test system can be appropriately challenged.
EQA can also be used as a means of detecting deficiencies with IQC. For example, some IQC providers supply assayed IQC material with very wide acceptable limits, with 2SD often +/- 20% from target value. For this reason, labs may believe their performance is good, but when scrutinized by EQA with narrow acceptable limits, performance will be identified as substandard.
What to Look for in a Good EQA Scheme
Laboratories can join either Local, National or International EQA schemes. An International EQA scheme would provide the best return on investment due to the higher peer group size and more diverse demographic of participants. Some key factors which typify a good quality EQA scheme include:
- Accreditation to ISO 17043 – Being accredited to this standard ensures the EQA scheme is fit for purpose
- Frequent Distribution – Regular EQA analysis allows for rapid identification of errors and any necessary corrective actions can be taken as soon as possible
- Large Number of Participants – Ensures an extensive database of results for a range of analytical methods and instruments. In addition, larger participant groups increase statistical validity of results
- Clinically Relevant Ranges – Analytes should be present at both normal and abnormal ranges, as to ensure medical decision limits are adequately tested
- Comprehensive Reports – Much of the value of participating in an EQA scheme lies in the report generated by the provider. Reports should be comprehensive, providing a range of statistical metrics and charts
How can Randox Help?
The Randox International Quality Assessment Scheme (RIQAS) incorporates all the above features, as well as many others, into the world’s most comprehensive EQA scheme. With more than 45,000 participants worldwide, RIQAS offers unrivalled peer group comparison, and has earned its place as the most popular EQA scheme in the world.
An EQA scheme operates like an early warning system; it can alert the lab and document the need for, stimulate and monitor improvement. However, the improvements themselves must be implemented and maintained by the lab.
Investment in a good EQA scheme can save labs a substantial amount of time and money, so it is worthwhile to invest wisely.
To sign up for RIQAS or to learn more, sign up using the form below!
- World Health Organisation, Laboratory Methods For Diagnosis Of HIV Infection In Infants And Children. Geneva: World Health Organisation. 2010;5.
- Fearon M. The laboratory diagnosis of HIV infections. The Canadian Journal of Infectious Diseases & Medical Microbiology. 2005;16(1):26-30.
In a QC survey conducted this year, Sten Westgard reached out to more than 45,000 laboratory professionals to gain a comprehensive view of the world’s Quality Control practices. It was one of the largest surveys that have been conducted and shared publicly.
Read on as we take a summarised look at our favourite bits.
Setting control Limits
Most labs are using their actual performance to set their mean and SD, however, a large percentage of labs still use manufacturer’s ranges, peer group ranges, and other non-individual sources for SD. These ranges can typically be set wider than they would if the ranges were based on their actual mean and SD. This can result in labs releasing incorrect patient results.
Laboratories were asked if they used 2 SD control limits on all tests and it was found that a majority use 2 SD. The strict use of 2 SD can generate a high level of false rejections (9% for two controls and higher for three). This causes a high level of out-of-control events; the use of QC multi-rules is recommended.
The types of Controls used by labs
More than 60% of labs were found to be using manufacturer controls, the drawbacks of which are well known. The latest ISO standards strongly encourage the use of independent / third-party controls. Westgard speculates that this will become a mandatory requirement in the next version of ISO 15189.
Frequency of QC
The first question about frequency asked how often labs ran QC during a run. Respondents reported how often they schedule QC in their labs. Around half only run QC at the beginning of a run with labs running it throughout the day coming in close second. A small proportion of labs reported running QC at both the beginning and the end of a run.
The final, least popular option involves spacing out QC based on test volume, the most scientific method determining how many patient samples can be run between controls without raising the risk of unacceptable results.
The next question asked about the overall frequency of QC. Most labs are meeting the once-a-day minimum standard for CLIA regulations.
“QC frequency remains primarily based on the rotational speed of the earth, not driven by needs of the clinician and patient.” – Sten Westgard
QC Frequency Influences
Regulator and accreditation requirements lead the way in influencing the frequency of QC with manufacturer recommendations, and professional judgement following close behind. Only a quarter of labs use the volume of testing to guide their QC frequency and one in six look to EP23 or IQCP for guidance.
Most labs are using on-board instrument informatics to support their QC charting, followed by LIS charting programs, and peer group software.
Of significance is the number of labs using Excel spreadsheets as their primary QC tool as well as standalone QC programs or even manual graph paper. This could be due to varying technological capabilities where some locations may not have access to, or the funds to afford, informatics.
A combined third of labs are out-of-control every day. In some labs this could be the result of running such a high volume of controls that false rejections are inevitable. However, rationalising in this way can lead to ‘alert fatigue’, where users begin to ignore alert flags and stop troubleshooting.
More than a quarter of labs have an out-of-control flag every few days while another roughly one in six have just one per week. A small number of labs report having few QC flags.
Managing QC Costs
Finally, laboratories were asked about the steps they take to manage QC costs. 60% claimed that they take no steps to manage costs. One in six reduced QC frequency, one in eight switched to cheaper controls, while, worryingly, almost one in ten changed their QC rules or widened limits.
Westgard’s Global QC Survey suggests there exists many inefficient implementations of Quality Control, with plenty of room for improvement. The current state of QC is, like many aspects of healthcare, unsustainable. Labs must adopt better approaches or risk their continuing feasibility, or worse, their patient’s results.
How Randox Can Help
Westgard highlights particular issues with labs mismanaging costs, still using manufacturer controls, and setting control limits – this is where Randox comes in.
Acusera Third Party Controls offer the highest quality solution for any lab – regardless of size or budget. Designed to provide an unbiased, independent assessment of performance, our internal quality controls have not been manufactured in line with, or optimised for use with any particular reagent, method or instrument helping you to easily meet ISO 15189 recommendations. Unrivaled consolidation allows for significant cost savings.
Acusera 24•7 Live Online allows you to automatically apply multi-rules and generate charts to help with setting accurate control limits, helping you get your quality control under control.
Reference: Westgard, S (2017), The 2017 Great Global QC Survey Results
To learn more about how Randox Quality Control can help you improve your QC visit the pages below or fill out the contact form and someone will be in touch.
World Diabetes Day
With World Diabetes Day on Tuesday 14th November 2017, we take a look at what diabetes is and why quality control is so important.
What is Diabetes?
Diabetes is a life-long condition which occurs when the glucose level in the blood is too high because it can’t enter the body’s cells to be used as fuel. There are two types of diabetes: type 1 and type 2. They are distinct conditions and must be treated and managed differently.
Type 1 Diabetes
Type one diabetes is an autoimmune condition in which the body attacks insulin-producing cells, this causes a lack of insulin, leading to an increased blood glucose level. Around 10% of people with diabetes has type 1.
Type 2 Diabetes
A mixture of genetic and environmental factors causes type 2 diabetes. The body doesn’t make enough insulin or the insulin it does create does not work correctly, leading to a glucose build up in the blood. It’s thought that up to 58% of type 2 diabetes can be prevented or delayed through healthy lifestyle choices.
Role of Quality Control
Quality control plays a crucial role in ensuring accurate and reliable diabetes monitoring. 70% of medical decisions are based on a laboratory test result and QC is vital in ensuring the results the laboratory report are both accurate and reliable.
Want to know what makes a good HbA1c control? Read on to find out.
Clinically Relevant Levels
In the diagnosis of diabetes, glycated haemoglobin (HbA1c) in blood provides an indication of average blood glucose levels in the previous three months. HbA1c is the recommended standard of care for type 2 diabetes monitoring. HbA1c is measured using the range below:
HbA1c – Clinically Relevant Levels
|Normal||Below 42 mmol/mol||Below 6.0%|
|Prediabetes||42 to 47 mmol/mol||6.0% to 6.4%|
|Diabetes||48 mmol/mol or over||6.5% or over|
It is important to assess the full clinical range of an assay, i.e. the range between the lowest and highest results which can be reliably reported. 48 mmol/mol is the cut-off for diabetes diagnosis, it is crucial that this can be measured accurately because any inaccuracy could mean the difference between being diagnosed and treated and not.
In terms of accreditation, ISO 15189:2012 states, ‘The laboratory should choose concentrations of control materials wherever possible, especially at or near clinical decision values, which ensure the validity of decisions made’.
Benefits of Third Party Controls
The importance of third party controls is evident. Third party controls can help identify instrument, reagent, and procedural errors. Unchecked these errors could lead to incorrect patient results, further leading to misdiagnosis.
Third party quality control material has not been designed or optimised for use with any instrument, kit, or method. This complete independence enables the quality control material to closely mirror the performance of patient samples, and in doing so, provide an unbiased, independent assessment of analytical performance across multiple platforms.
Again, in terms of accreditation, ISO 15189 states – “use of independent third party control material should be considered, either instead of, or in addition to, any control materials supplied by the reagent or instrument manufacturer.”
Many laboratories perform HbA1c testing on a dedicated machine and as a result, are not always using a third party control.
Wastage is a common issue when running HbA1c due to the pre-treatment step required for many HbA1c controls and poor stability of some controls on the market. Look out for controls with an extended open vial stability to help reduce waste and keep costs low.
How can Randox help?
To help you get your QC in check for World Diabetes Day, Randox Acusera HbA1c control contains both HbA1c and Total Haemoglobin, with a reconstituted stability of 4 weeks to reduce waste and reduce costs. To find out more about our HbA1c control visit the page using the button below or fill out the form above.
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