Clinical Chemistry Podcast

A Review appearing in the October 2018 issue of Clinical Chemistry describes the trends and the technologies that have emerged in the past decade and are shaping contemporary point-of-care testing. We are joined by the Review's first author, Dr. Ping Wang. She is Associate Professor of Pathology and Laboratory Medicine at the University of Pennsylvania, and Director of Clinical Chemistry and Core Laboratory at the Hospital of the University of Pennsylvania.

Standardization efforts for amylase have been limited by a lack of commutability in the current certified reference material. New candidate reference materials have been developed to potentially overcome this limitation, facilitating their use for calibration and trueness control of routine measurement systems. An original article appearing in the August of 2018 issue of Clinical Chemistry describes the commutability assessments of these new candidate reference materials for pancreatic alpha amylase. The authors investigated if a reference material with an artificial matrix could be commutable for routine methods and compared to different statistical approaches to assess the commutability of the candidate reference materials.

Previously, carrier screening has been used in at-risk and specific ethnic populations, or for a limited number of diseases. The broader screening approach, called expanded carrier screening, was endorsed in 2017 by the American College of Obstetricians and Gynecologists as an acceptable strategy for preconception and prenatal carrier screening. This is expected to have a significant clinical impact, as targeted screening approaches likely have missed a large number of affected pregnancies due to the limited conditions tested, the unknown ethnic ancestry of many individuals, and the fact that the majority of children born with a genetic disease have no family history of the condition. When provided with results that their pregnancy is at-risk for a severe condition, study show approximately 80% of such couples pursue alternative reproductive options. Given these consequences and the relative rarity of the included diseases, expanded carrier screening panels must have a high detection rate to correctly identify at-risk couples, and to minimize the residual risk when only one partner is tested positive. Though next generation sequencing has revolutionized genetic testing as a whole, advances in detecting copy number variants by next generation sequencing have been critical to improving the analytical quality of expanded carrier screening panels.

An original research article appearing in the July 2018 issue of Clinical Chemistry describes these achievements while establishing the analytical validity of expanded carrier screening and quantifying how many pregnancies could be impacted by this approach in the general U.S. population.

Test standardization is a complex and multifaceted effort that's remained a major goal for laboratory medicine's professional societies, including the AACC and IFCC. Hemoglobin A1c is an example of a test that has undergone global standardization due to its worldwide importance in diabetes screening, diagnosis, and care. A key part of any standardization effort is aligning all manufacturers' methods to an accepted reference method. This was the main aim of the European Hemoglobin A1c trial devised by the IFCC's Committee on Education and Use of Biomarkers in Diabetes. The August 2018 issue of Clinical Chemistry includes an original research article that describes the European Hemoglobin A1c trial and its results.

Proper handling during the collection and processing of specimens is crucial for producing reliable results. These pre-analytical steps are highly vulnerable to the introduction of experimental bias and variance, which may drastically degrade specimen quality. Analytes are affected differently by uncontrolled variations in specimen collection, processing, and storage protocols. The August 2018 issue of Clinical Chemistry includes a Review article from the Precision Medicine and Pharmacometabolomics Task Group of the Metabolomics Society. The authors summarize the current variability among pre-analytical processing and biobanking procedures for metabolomics research and provide recommendations for best practices.

According to the World Health Organization, type 2 diabetes comprises the majority of the more than 400 million people with diabetes around the world. In efforts to better understand the disease, metabolomics measurements have identified tryptophan metabolites as potential biological mediators in the development of type 2 diabetes. The PREDIMED trial was a multi-center trial of Mediterranean-style diets where the primary prevention of cardiovascular events that also included type 2 diabetes as a secondary end point. An original research article published in the August 2018 issue of Clinical Chemistry studies whether tryptophan metabolites in PREDIMED participants were associated with development of type 2 diabetes and insulin resistance.

It was once thought that RNA only existed within cells. However, recent discoveries show that RNA is exported from cells and may be functional in cell to cell communication. This extracellular RNA can be abundant and stable and is found in bodily fluids such as saliva. Saliva has long been of interest for biomarker discovery and development, given its noninvasiveness and relative ease of collection.

Despite these advantages, use of saliva for understanding more about extracellular RNA and its role in human biology and disease through RNA sequencing has some challenges. The high bacterial content and low abundance of extracellular RNA in saliva mean that optimization of RNA library construction and isolation protocols are critical to the success of these RNA sequencing experiments.

An original research article in the July 2018 issue of Clinical Chemistry compares different RNA isolation methods and library construction kits for long and small RNA sequencing of salivary extracellular RNA. The authors described which protocols provide the best RNA yield and detection by next generation sequencing.

Liquid biopsy methods are an exciting area in cancer screening, diagnosis, and management. These methods are aimed at measuring genomic signatures of tumor cells in the blood. They rely on detection of circulating tumor cells, tumor-derived extracellular vesicles, or exosomes, or cell-free circulating DNA. Liquid biopsy methods have been proposed to compliment, enhance or perhaps even replace tissue biopsy in some scenarios. Liquid biopsy methods are an exciting area in cancer screening, diagnosis, and management. These methods are aimed at measuring genomic signatures of tumor cells in the blood. They rely on detection of circulating tumor cells, tumor-derived extracellular vesicles, or exosomes, or cell-free circulating DNA. Liquid biopsy methods have been proposed to compliment, enhance or perhaps even replace tissue biopsy in some scenarios.

Beyond the minimal invasiveness, performing liquid biopsy may overcome some other weaknesses of tissue biopsy that are related to a single site's inability to capture intratumor heterogeneity or be representative of all the changes within the tumor. All three approaches to detect a tumor's genetic material have been applied for therapy stratification and monitoring in breast cancer. However, knowledge about the differences between these methods in the same patient cohort is limited.

An original article in the July 2018 issue of Clinical Chemistry compared messenger RNA profiles of circulating tumor cells and extracellular vesicles in patients with metastatic breast cancer to estimate the utility of each in therapy management.

Laboratory testing is a key component of models of care for all types of lipid disorders. New therapies demand accuracy of dyslipidemia testing at very low LDL cholesterol concentration ranges. Inaccurate results lead to incorrect diagnosis and therapeutic management, both of which are costly to society and harmful to patients. To address these key issues of lipoprotein and apolipoprotein markers and reach consensus on contemporary lipid testing, a multidisciplinary panel was established by the European Federation of Clinical Chemistry and Laboratory Medicine and the European Atherosclerosis Society. The July 2018 issue of Clinical Chemistry includes a special report from this joint consensus initiative. It provides recommendations for improving the use of the lipid profile to assess cardiovascular disease risk conferred by atherogenic lipoproteins.

Cardiac troponins are recognized as the primary biomarkers used in the diagnosis of acute myocardial infarction. These are commonly detected by immunoassays, which offer the wide availability and rapid results needed in clinical care scenarios to rule out myocardial infarction. However, immunodetection methods can be limited when there is degradation of the target analyte, as is the case with cardiac troponin I. Early studies suggested that the central region, located between amino acid residues 30 and 110, was the most stable part of the molecule. This was a driver for the majority of current diagnostic systems to utilize antibodies with epitopes located within the central region. A down side to this approach is that auto antibodies also bind to this region, potentially causing interference and erroneous results.

As more recent studies have identified additional cardiac troponin I proteolytic fragments, it is important to understand their composition and prevalence in the blood of patients with acute myocardial infarction. Furthermore, there is a need to evaluate whether monoclonal antibodies specific to the regions beyond the central section of the molecule can be used to develop cardiac troponin I assays with improved performance over those currently available. An original article appearing in the July 2018 issue of Clinical Chemistry describes a study investigating these concepts.