HbA1c testing at the point-of-care: Comparison against international quality standards
Many disorders rely on specific measurement of blood parameters, for example blood sugar, as an essential part of their diagnostic and treatment monitoring procedures. In the past, blood parametric tests were performed exclusively in a clinical laboratory.
Newer developments in testing technologies have allowed some of these, including glycated hemoglobin testing to be carried out in point of care settings such as a clinic or doctor’s surgery. The greatest advantage to point-of-care-testing (POCT) is the time saved in making clinical decisions on patient management without having to wait for the test results to arrive from the laboratory.
POCT has taken a prominent place in the delivery of healthcare services, by promising and providing quicker service. Patients who are very sick can now be rapidly and accurately assessed, while the frequency of outpatient visits is also reduced. For this reason POCT has every reason to be a valuable tool to enhance patient care and treatment and improve patient satisfaction.
POCT is usually carried out by healthcare professionals who have little to no experience with laboratory testing, making it imperative that such tests are reproducible and simple to perform, while yielding reliable data.
Another important consideration is that these tests should match the quality of traditional laboratory analyzers. Unreliable results would be unusable and irrelevant despite the time savings, as decisions taken on this basis could often be wrong.
One area where POCT has proved its worth is in the diabetes clinic. High glucose levels can produce a host of serious medical complications if not corrected promptly. Therefore, keeping track of blood sugar levels in diabetic patients is important, requiring regular measurement of glycated hemoglobin levels (HbA1C levels).
Glycated hemoglobin is hemoglobin with bound glucose molecules. This typically occurs to a limited extent in regular blood but occurs with a higher incidence with very high blood glucose concentrations. The HbA1C test reflects the binding of glucose to hemoglobin in a quantitative manner. As the average lifespan of a normal red blood cell is about 120 days, the result can show the average glucose concentration in blood over the past three months.
Standardized HbA1C performance criteria have recently been issued, which allow direct correlation between the test results and the conclusions of the Diabetes Control and Complications Trial and the United Kingdom Prospective Diabetes Study. These trials showed that the level of HbA1C was directly related to the risk of various outcomes in diabetic patients4.
Devices used for POCT
A host of POCT devices are now available, and many have obtained certification of compliance to relevant regulatory criteria put forward by regulatory bodies. Including CE certification, which shows that it conforms to the EU directives on health, safety or environmental protection; and the US Food and Drug Administration (FDA) approval.
However, it must be understood, that the certificate of compliance is based upon the manufacturer’s data, which in turn is obtained under ideal operating conditions. However, this is not likely to be the case during actual POCT due to the wide variations in clinical conditions. Thus, there is no guarantee that the certification proves that the instrument will function just as reliably in real-life situations2.
One way to provide reliable assessment in real world scenarios is through external quality assessment (EQA) tools and trials2,3. This is only possible for instruments which are enrolled in this type of scheme. To make it more difficult, some devices are designed to prevent any internal quality assessments to verify device calibration. Independent laboratory testing is often needed to assess the actual reliability of the data gathered by these POCT devices under the conditions of daily clinical use.
Devices for HbA1c Point-of-care Testing
As of now more than 30 POCT devices are offered for HbA1C testing. This has led to the establishment of support and reference values for manufacturers, provided by the European Reference Laboratory for Glycohemglobin, so that the instruments may be evaluated for their analytical performance independently5.
In a study, the Clinical and Laboratory Standards Institute (CLSI) protocols were applied to measure the accuracy and precision of an array of POCT devices for HbA1C testing, against the measurement procedures set out by International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) as secondary reference values. These findings were published in the Journal of Diabetes Science and Technology6.
Of the tested devices, three are based on a boronate affinity methodology, namely, Quo-Lab (EKF Diagnostics PLC, Cardiff, UK), Afinion2™ (Abbott, Oslo, Norway), and HbA1c 501 (HemoCue Diagnostics, Ängelholm, Sweden). One uses the enzymatic protocol to determine HbA1c (A1Care (i-SENSE, Seoul, Korea).
The results for the Quo-Lab and the Afinion2 were shown to be excellent. They both conformed to the NGSP criteria when tested against four of the secondary reference measurement protocols. The HbA1c 501 achieved acceptable (borderline) analytical results, even though it complied with the criteria for routine laboratory procedures. However, the A1Care instrument did not pass any of the tested criteria, and yielded results that fell below acceptable values for the determination of HbA1c6.
This recent data is mentioned to emphasize the careful selection that should go into picking a POCT device. Of course, these instruments are constantly undergoing innovation to obtain better analytical performance. Yet the danger remains that all POCT devices may not yield reliable data for HbA1C determination, and thus the evidence must be reviewed carefully before choosing an instrument for point-of-care measurements. Robust independent evaluations of POCT device accuracy thus remain invaluable for assisting such decision making and ensuring that the best patient care is provided.
- Patzer KH, et al. Implementation of HbA1c point of care testing in 3 German Medical Practices: impact on workflow and physician, staff, and patient satisfaction. J Diabetes Sci Technol. 2018; 3:687‑694.
- NGSP website note CAP survey data. Available at: http:// www.ngsp.org/CAP/CAP17c.pdf Accessed April 2018.
- Centers for Medicare & Medicaid Services. Available at: https://www.cms.gov/Regulations-and-Guidance/Legislation/CLIA/Certificate_of_-Waiver_Laboratory_Project.html. Accessed April 2018.
- NGSP. Harmonizing hemoglobin A1c testing. Available at: www.ngsp.org
- Westgard. Available at: http://james.westgard.com/the_westgard_rules/2017/08/are-there-new-erna-lenters-westra-rulesfor-hba1c.html. Accessed April 2018.
- Lenters-Westra E and English E. Evaluation of Four HbA1c Point-of-Care Devices Using International Quality Targets: Are They Fit for the Purpose? Journal of Diabetes Science and Technology 2018; Special Issue: 1–9.
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