MSACL Conference Schedule

Establishing the Metrological Basis: The Work of NIST on Establishing Traceability in Laboratory Medicine
Tue 3:30 PM - Session: Regulations and Standards
David M. Bunk
In medicine, the diagnosis, risk assessment, and treatment of patients depends on accurate and precise laboratory measurements of a wide range of clinical analytes. To assure measurement quality in laboratory medicine, a reference measurement system must be established. The essential components of a reference measurement system in clinical chemistry are: the definition of the measurand, reference measurement procedures, and reference materials.

Once established, the reference measurement system links a patient's laboratory measurement result to an established higher-order standard (ideally, an SI-unit such as the mole, gram, or katal) through an unbroken chain of comparisons. Linked within this metrological traceability chain are national metrology institutes, such as NIST, which provide primary and secondary reference materials and reference measurement procedures, accredited reference measurement labs, which provide secondary reference materials and measurement procedures, the manufacturers of clinical assays, which provide calibrators and control samples, and clinical diagnostic laboratories.

The establishment of reference measurement systems for routine clinical analytes has been an ongoing and critical effort carried out through partnerships of national metrology institutes, academic institutes, and professional societies in clinical chemistry, such as the AACC and the IFCC. The results of almost four decades of this work has established reference measurement systems for a large number of well-characterized clinical analytes like cholesterol, glucose, creatinine, and blood electrolytes, just to name a few. The example of the reference measurement system for cholesterol will be highlighted as an example. However, this effort has yet only been applied in a limited fashion to more complex, heterogeneous clinical analytes such as proteins. Clinical protein analytes represent unique challenges to standardization efforts due to their inherent chemical and conformational heterogeneity, stability, availability, and their antigenicity relative to the plurality of antibodies used in clinical immunoassay.

The efforts at NIST to establish a reference measurement system for a cardiac marker, human cardiac troponin I, will be used to highlight the challenges faced in the standardization of clinical protein measurement.