Results between different clinical laboratory measurement procedures (CLMP) should be equivalent, within clinically meaningful limits, to enable optimal use of clinical guidelines for disease diagnosis and patient management. When laboratory test results are neither standardized nor harmonized, a different numeric result may be obtained for the same clinical sample. Unfortunately, some guidelines are based on test results from a specific laboratory measurement procedure without consideration of the possibility or likelihood of differences between various procedures. When this happens, aggregation of data from different clinical research investigations and development of appropriate clinical practice guidelines will be flawed. A lack of recognition that results are neither standardized nor harmonized may lead to erroneous clinical, financial, regulatory, or technical decisions.
Standardization of CLMPs has been accomplished for several measurands for which primary (pure substance) reference materials exist and/or reference measurement procedures (RMPs) have been developed. However, the harmonization of clinical laboratory procedures for measurands that do not have RMPs has been problematic owing to inadequate definition of the measurand, inadequate analytical specificity for the measurand, inadequate attention to the commutability of reference materials, and lack of a systematic approach for harmonization. To address these problems, an infrastructure must be developed to enable a systematic approach for identification and prioritization of measurands to be harmonized on the basis of clinical importance and technical feasibility, and for management of the technical implementation of a harmonization process for a specific measurand.
BACKGROUND: Viral load testing for cytomegalovirus (CMV) is an important diagnostic tool for the management of transplant recipients and immunocompromised individuals; however, inconsistency among laboratories in quantitative measurements of viral load limits interinstitutional comparisons. These inconsistencies stem from the lack of assays cleared by the US Food and Drug Administration, the absence of international standards, the wide variety of CMV-extraction and -detection methods, and differences in materials used for calibration. A critical component of standardization is the use of calibrators that are traceable and commutable.
Commutability of quantitative reference materials has proven important for reliable and accurate results in clinical chemistry. As international reference standards and commercially produced calibration material have become available to address the variability of viral load assays, the degree to which such materials are commutable and the effect of commutability on assay concordance have been questioned. To investigate this, 60 archived clinical plasma samples, which previously tested positive for cytomegalovirus (CMV), were retested by five different laboratories, each using a different quantitative CMV PCR assay. Results from each laboratory were calibrated both with lab-specific quantitative CMV standards ("lab standards") and with common, commercially available standards (
In recent years, the mutational status of the KRAS oncogene has become incorporated into standard medical care as a predictive marker for therapeutic decisions related to patients with metastasized colorectal cancer. This is necessary, because these patients benefit from epidermal growth factor receptor (EGFR)-targeted therapy with increased progression-free survival only if the tumor does not carry a mutation in KRAS. Many different analytical platforms, both those commercially available and those developed in house, have been used within pathology laboratories to assess KRAS mutational status. For a testing laboratory to become accredited to perform such tests, it is essential that they perform reliability testing, but it has not previously been possible to perform this kind of testing on the complete workflow on a large scale without compromising reproducibility or the mimicry of the control sample. We assessed a novel synthetic control for formalin-fixed, paraffin-embedded (FFPE) tumor samples in a blind study conducted within nine laboratories across Europe. We show that FFPE material can, at least in part, mimic clinical samples and we demonstrate this control to be a valuable tool in the assessment of platforms used in testing for KRAS mutational status.
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