Standardization activities for harmonization of test results

Metrological sharp shooting for plasma proteins and peptides: The need for reference materials for accurate measurements in clinical proteomics and in vitro diagnostics to generate reliable results

Reliable study results are necessary for the assessment of discoveries, including those from proteomics. Reliable study results are also crucial to increase the likelihood of making a successful choice of biomarker candidates for verification and subsequent validation studies, a current bottleneck for the transition to in vitro diagnostic (IVD). In this respect, a major need for improvement in proteomics appears to be accuracy of measurements, including both trueness and precision of measurement. Standardization and total quality management systems (TQMS) help to provide accurate measurements and reliable results. Reference materials are an essential part of standardization and TQMS in IVD and are crucial to provide metrological correct measurements and for the overall quality assurance process. In this article we give an overview on how reference materials are defined, prepared and what role they play in standardization and TQMS to support the generation of reliable results. We discuss how proteomics can support the establishment of reference materials and biomarker tests for IVD applications, how current reference materials used in IVD may be beneficially applied in proteomics, and we provide considerations on the establishment of reference materials specific for proteomics. For clarity, we solely focus on reference materials related to serum and plasma.

Protein biomarker discovery and validation: the long and uncertain path to clinical utility

Better biomarkers are urgently needed to improve diagnosis, guide molecularly targeted therapy and monitor activity and therapeutic response across a wide spectrum of disease. Proteomics methods based on mass spectrometry hold special promise for the discovery of novel biomarkers that might form the foundation for new clinical blood tests, but to date their contribution to the diagnostic armamentarium has been disappointing. This is due in part to the lack of a coherent pipeline connecting marker discovery with well-established methods for validation. Advances in methods and technology now enable construction of a comprehensive biomarker pipeline from six essential process components: candidate discovery, qualification, verification, research assay optimization, biomarker validation and commercialization. Better understanding of the overall process of biomarker discovery and validation and of the challenges and strategies inherent in each phase should improve experimental study design, in turn increasing the efficiency of biomarker development and facilitating the delivery and deployment of novel clinical tests.

The efficacy of cystatin C assay in the prediction of glomerular filtration rate. Is it a more reliable marker for renal failure?

We determined the sensitivity, specificity, receiver operating characteristics and correlation between cystatin C (cysC) and two widely used markers of renal function, creatinine clearance and serum creatinine, in 244 patients (84 diabetics, 84 hypertensive and 76 healthy subjects). Renal failure was defined as creatinine clearance of less than either 80 or 60mL/min. Variables were evaluated for two definitions of renal failure and compared between patient groups. Correlation coefficients with cysC were −0.87 for creatinine clearance and 0.92 for creatinine in patients with hypertension; −0.90 for creatinine clearance and 0.97 for creatinine in diabetics; and −0.61 for creatinine clearance and 0.94 for creatinine in the control group. The receiver operating characteristic curves with a cut-off value of 60mL/min were similar for creatinine and cysC, while at 80mL/min they were 0.626 for creatinine and 0.813 for cysC levels. We classified the patients into three groups with respect to creatinine clearance (1, >80mL/min; 2, 60–80mL/min; 3, <60mL/min). Mean creatinine (p<0.0001) and cysC (p<0.0001) levels were significantly different between all the groups. Sensitivity, specificity and predictive values were higher for cysC levels, particularly in diabetics and hypertensive patients. The current study suggests that cysC is preferable for detecting temporal changes in renal function in the early stages of renal insufficiency.