An Appeal to Medical Journal Editors: The Need for a Full Description of Laboratory Methods and Specimen Handling in Clinical Study Reports

Biochemically Tracked Variability of Blood Plasma Thawed-State Exposure Times in a Multisite Collection Study

The integrity of blood plasma/serum (P/S) specimens can be impacted by preanalytical handling and storage conditions that result in thawed-state exposures (> -30°C). We recently reported a simple dilute-and-shoot, intact-protein liquid chromatography/mass spectrometry (LC/MS) assay called ΔS-Cys-Albumin that quantifies cumulative exposure of P/S to thawed conditions based on the change in relative abundance of the oxidized (S-cysteinylated) proteoform of albumin (S-Cys-Albumin) in the native sample to that of an aliquot of the sample intentionally driven to its maximum oxidation state. Herein, we evaluated the effect of prestorage delay and initial storage temperature on sample integrity by applying the ΔS-Cys-Albumin assay to a set of plasma samples (n = 413) collected under a single clinical study but from 12 different collection sites. Major differences (p < 0.0001) were observed between different groups of samples with modestly inconsistent initial handling conditions (i.e., initial processing of whole blood to plasma and placement at -80°C completed in under 3 hours, 3-13 hours, and over 17 hours). ΔS-Cys-Albumin was significantly inversely correlated with delay time at 4°C before centrifugation and total delay before final storage at -80°C (p < 0.0001). Samples from two collection sites had much lower ΔS-Cys-Albumin values relative to samples from other sites, in accordance with the fact that they were stored at -20°C for an average of 7.6 months before shipment to the central repository for final storage at -80°C. Based on the rate law for S-Cys-Albumin formation in plasma ex vivo, the average time that each plasma specimen had been exposed to the equivalent of room temperature (23°C) was back calculated from the measured ΔS-Cys-Albumin values. A survey of clinical analytes in P/S whose measured concentrations are sensitive to the initial handling/storage conditions documented in this study is provided and the ramifications of the plasma integrity findings from this multisite clinical study are discussed.

Delta-S-Cys-Albumin: A Lab Test that Quantifies Cumulative Exposure of Archived Human Blood Plasma and Serum Samples to Thawed Conditions

Exposure of blood plasma/serum (P/S) to thawed conditions (> -30 °C) can produce biomolecular changes that skew measurements of biomarkers within archived patient samples, potentially rendering them unfit for molecular analysis. Because freeze-thaw histories are often poorly documented, objective methods for assessing molecular fitness before analysis are needed. We report a 10-μl, dilute-and-shoot, intact-protein mass spectrometric assay of albumin proteoforms called "ΔS-Cys-Albumin" that quantifies cumulative exposure of archived P/S samples to thawed conditions. The relative abundance of S-cysteinylated (oxidized) albumin in P/S increases inexorably but to a maximum value under 100% when samples are exposed to temperatures > -30 °C. The difference in the relative abundance of S-cysteinylated albumin (S-Cys-Alb) before and after an intentional incubation period that drives this proteoform to its maximum level is denoted as ΔS-Cys-Albumin. ΔS-Cys-Albumin in fully expired samples is zero. The range (mean ± 95% CI) observed for ΔS-Cys-Albumin in fresh cardiac patient P/S (n = 97) was, for plasma 12-29% (20.9 ± 0.75%) and for serum 10-24% (15.5 ± 0.64%). The multireaction rate law that governs S-Cys-Alb formation in P/S was determined and shown to predict the rate of formation of S-Cys-Alb in plasma and serum samples-a step that enables back-calculation of the time at which unknown P/S specimens have been exposed to room temperature. A blind challenge demonstrated that ΔS-Cys-Albumin can detect exposure of groups (n = 6 each) of P/S samples to 23 °C for 2 h, 4 °C for 16 h, or -20 °C for 24 h-and exposure of individual specimens for modestly increased times. An unplanned case study of nominally pristine serum samples collected under NIH-sponsorship demonstrated that empirical evidence is required to ensure accurate knowledge of archived P/S biospecimen storage history.

Circulating microRNA in cardiovascular disease

Acute myocardial infarction (AMI) and heart failure (HF) are two major causes of cardiovascular mortality and morbidity. Early diagnosis of these conditions is essential to instigate immediate treatment that may result in improved outcomes. Traditional biomarkers of AMI include cardiac troponins and other proteins released from the injured myocardium but there are a number of limitations with these biomarkers especially with regard to specificity. In the past few years circulating nucleic acids, notably microRNA that are small non-coding RNAs that regulate various cellular processes, have been investigated as biomarkers of disease offering improved sensitivity and specificity in the diagnosis and prognostication of various conditions. In this review, the role of microRNAs as biomarkers used in the diagnosis of AMI and HF is discussed, their advantage over traditional biomarkers is outlined and the potential for their implementation in clinical practice is critically assessed.

Validation of new cancer biomarkers: a position statement from the European group on tumor markers

BACKGROUND

Biomarkers are playing increasingly important roles in the detection and management of patients with cancer. Despite an enormous number of publications on cancer biomarkers, few of these biomarkers are in widespread clinical use.

CONTENT

In this review, we discuss the key steps in advancing a newly discovered cancer candidate biomarker from pilot studies to clinical application. Four main steps are necessary for a biomarker to reach the clinic: analytical validation of the biomarker assay, clinical validation of the biomarker test, demonstration of clinical value from performance of the biomarker test, and regulatory approval. In addition to these 4 steps, all biomarker studies should be reported in a detailed and transparent manner, using previously published checklists and guidelines. Finally, all biomarker studies relating to demonstration of clinical value should be registered before initiation of the study.

SUMMARY

Application of the methodology outlined above should result in a more efficient and effective approach to the development of cancer biomarkers as well as the reporting of cancer biomarker studies. With rigorous application, all stakeholders, and especially patients, would be expected to benefit.

AST/ALT ratio is not an index of liver fibrosis in chronic hepatitis C when aminotransferase activities are determinate according to the international recommendations

OBJECTIVE

The aspartate aminotransferase activity (AST)/alanine aminotransferase activity (ALT) ratio is used as liver fibrosis index whereas the reported data are conflicting. In chronic hepatitis C (CHC), reported diagnostic accuracies range from none to good for significant fibrosis and to excellent for cirrhosis. Assuming that AST/ALT increases are mainly due to vitamin B6 defects since pyridoxal phosphate (PLP), active form of B6, acts as coenzyme in transamination reactions, we evaluated the diagnostic accuracy of the AST/ALT ratio using standardized methods for AST and ALT activities, with PLP addition as recommended, in a prospective multicenter cohort of CHC patients.

METHODS

ALT and AST activities were measured using the recommended IFCC methods with addition of pyridoxal 5'-phosphate. We evaluated the AST/ALT ratio for the diagnosis of liver fibrosis or cirrhosis in a cohort of CHC patients included in a multicenter prospective study. A liver biopsy was performed in each patient and reviewed by two independent pathologists in order to determine the fibrosis stage according to Metavir classification which was the reference standard.

RESULTS

AST/ALT ratio significantly increased with histological stage of liver fibrosis and there was a significant correlation between Metavir fibrosis stage and AST/ALT ratio (r=0.129, P<0.0035). The ROC curve analyses showed that the AST/ALT ratio does not discriminate significant fibrosis (F≥2) (AUROC=0.531) and had only very poor diagnostic accuracies for severe fibrosis (F≥3) (AUROC=0.584) or cirrhosis (F4) (AUROC=0.626).

CONCLUSION

AST/ALT ratio is not a good and discriminative index of liver fibrosis in CHC when aminotransferase activities are determinate according to the international recommendations.

Clinical Use and Measurement of Cardiac Troponin (cTn)

Cardiac troponins are cardio-specific and are widely used for the early diagnosis and triage of patients with acute coronary syndromes in conjunction with clinical history, electrocardiographic changes and imaging. Troponin is also useful for the prediction of outcomes in acute coronary syndromes, renal failure, sepsis, and critically ill patients. New developments in assay technology, designated as high sensitivity troponins, permit detection of lower levels of troponin in most healthy individuals, earlier diagnosis of myocardial infarction, and prognosis of stable coronary disease in the community.

Good mass spectrometry and its place in good science

The mass spectrometry community has expanded as instruments became more powerful, user-friendly, affordable and readily available. This opens up opportunities for novice users to perform high impact research, using highly advanced instrumentation. This introductory tutorial is targeted at the novice user working in a research setting. It aims to offer the benefit of other people's experiences and to help newcomers avoid known pitfalls and problematic issues. It discusses some of the essential features of sound analytical chemistry and highlights the need to use validated analytical methods that provide high quality results along with a measure of their uncertainty. Examples are used to illustrate potential pitfalls and their consequences.