Labs generally rely on external quality assessment (EQA) programs to help improve their performance, but an article in Clinical Biochemistry suggests these initiatives may also provide an opportunity to achieve measurement traceability.
EQA, a collaborative process in which labs assess their ability to measure a specific analyte, plays an important role in the traceability quest. However, it’s being underused at a time when labs are putting a premium on commutability and metrological traceability. To use EQA properly in the traceability quest, “laboratories need to understand the importance of using a range of values appropriate to the assay to identify areas of quality need,” according to authors Tony Badrick, PhD, Wilson Punyalack, and Peter Graham, who all work at the Royal College of Pathologists of Australasia Quality Assurance Programs in Sydney.
Traceability helps assure the accuracy and comparability of a patient’s lab results. “Establishing metrological traceability satisfies the basic requirements of evidence-based laboratory medicine. Thus, it improves patient care, disease control and prevention, and saves money by allowing the pooling of clinical trial data rather than repeating studies,” the authors wrote. According to Badrick, the study’s corresponding author, it’s also a key component of reducing patient risk, “particularly when using international guidelines or trials where there are decision levels to ensure that results obtained in any lab are comparable.”
EQA schemes are one of several essential pillars used to achieve comparable results, along with certified reference materials, reference methods, reference measurement services, and common reference intervals.
Badrick and his colleagues reviewed the many assets EQA brings to the table. It provides reliable information for replacing unsatisfactory methods, helps identify labs at risk for poor performance, and uses a variety of methods to identify and quantify the effects of interfering substances and to characterize test bias and imprecision. They lay out a “top-down” conventional traceability chain and, using conventional EQA samples, outline the role of EQA in a “bottom-up” model. “Top-down traceability tries to reduce intermethod bias; bottom up traceability identifies it,” Badrick explained to CLN Stat.
The conventional traceability chain starts with reference methods and reference materials in a reference laboratory. These help assign values to primary calibrators that subsequently assign values to a manufacturer’s master calibrator, using secondary methods in a manufacturer’s facility. The manufacturer then assigns values to its instrument calibrators using these methods and primary calibrators. These are used in routine laboratories to calibrate analyzers.
Laboratories in the bottom-up model run EQA/PT samples as patient samples. They compare these samples against their peers, using the same manufacturers’ instruments/reagents and master calibrators. “This process identifies laboratories with poor performance (different results to group) or where there is an issue with the manufacturer group having a bias. The EQA material must be commutable for this to work,” Badrick said.
Because problems exist with noncommutability in some EQA materials, it’s up to the EQA scheme to provide information about the material, Badrick said. “For laboratories using the same platforms, they should obtain the same results, and EQA provides this information, irrespective of whether the method is traceable to higher-order reference methods and materials.”
Laboratories should try to seek traceability through reference methods, materials, and other laboratories whenever possible. However, according to the Joint Committee for Traceability in Laboratory Medicine database of higher-order reference materials, measurement methods/procedures, and services, only 86 reference measurement procedures/methods and 155 certified reference materials exist. Labs don’t normally have direct access to reference methods or reference laboratories, either. They rely on manufacturers to ensure the traceability/commutability of their secondary calibrators.
“There have been instances where EQA has identified calibrators’ issues. So, in many cases the only remaining pillar is EQA,” Badrick said.&