Prerequisites for use of common reference intervals

The theory of reference values was developed more than 30 years ago, but its application in most clinical laboratories is still incomplete today. This is for several reasons, the most relevant ones being the lack of standardisation of the analytical methods, resulting in method-dependent values, and the difficulty in recruiting the proper number of reference subjects for establishment of reference intervals. With the recent progress in method standardisation the first problem is reducing while the second can be addressed optimally via multicentre collaborative studies that aim to establish common reference intervals. To be effective this approach requires the following prerequisites: 1) the existence of a reference measurement system for the analyte; 2) field methods producing results traceable to the reference system; and 3) a carefully planned multicentre reference interval study. Such a procedure will produce results traceable to the reference measurement system for a large number of reference subjects, under controlled pre-analytical conditions. It will also enable a better understanding of the various sources of population variability, if there is the need for partitioning of a reference interval or if there are any limitations to adopting the established reference intervals on a national or global scale. Once reference intervals are determined, clinical laboratories can adopt a common reference interval provided: 1) the population that the laboratory services is similar to the one studied; 2) methods producing traceable results are used; and 3) analytical quality is within defined targets of precision and bias. Moreover, some validation of the interval using a small sample of reference individuals from the laboratory's population is advisable.     

Soluble Itraconazole in Tablet Form Using Disordered Drug Delivery Approach: Critical Scale-up Considerations and Bio-equivalence Studies

The present research work explores formulation design, critical scale-up considerations and bio-equivalence studies of soluble itraconazole (ITZ) in a tablet form using disordered drug delivery approach. Disordered system of ITZ with a lower viscosity grade of hydroxypropyl methyl cellulose (Pharmacoat 603) was developed for the first time and extensively characterised at three different stages, namely development of glass system, pellet coating and tablet compression using advanced analytical techniques. Complete molecular embedment of ITZ resulting in amorphisation was observed and found to be sustained until end of the real-time and accelerated stability studies. Developed formulation exhibited comparative in vitro dissolution profile (similarity factor >70) with reference product (Sporanox, Janssen Pharmaceutica) in simulated gastric fluid without enzymes. Formulation was scaled up in three batches (50,000 tablets/batch) with detailed validation of critical process parameters using process capability index method. Critical scale-up considerations like control of residual solvent content, effect of pellet size on dissolution, process variables in pellet coating, compressibility of coated pellets and cushioning effect required for desired compressibility were thoroughly discussed. Bioequivalence study of single dose of test and reference product in seven healthy human volunteers under fed condition exhibited significant bioequivalence with results (AUC_last and AUC_∞) lying between 90% confidence interval. With increase in number of subjects to 24, a significant effect on pharmacokinetic parameters of both reference as well as developed ITZ tablets was observed.     

HUPO Plasma Proteome Project specimen collection and handling: towards the standardization of parameters for plasma proteome samples

There is a substantial list of pre-analytical variables that can alter the analysis of blood-derived samples. We have undertaken studies on some of these issues including choice of sample type, stability during storage, use of protease inhibitors, and clinical standardization. As there is a wide range of sample variables and a broad spectrum of analytical techniques in the HUPO PPP effort, it is not possible to define a single list of pre-analytical standards for samples or their processing. We present here a compendium of observations, drawing on actual results and sound clinical theories and practices. Based on our data, we find that (1) platelet-depleted plasma is preferable to serum for certain peptidomic studies; (2) samples should be aliquoted and stored preferably in liquid nitrogen; (3) the addition of protease inhibitors is recommended, but should be incorporated early and used judiciously, as some form non specific protein adducts and others interfere with peptide studies. Further, (4) the diligent tracking of pre-analytical variables and (5) the use of reference materials for quality control and quality assurance, are recommended. These findings help provide guidance on sample handling issues, with the overall suggestion being to be conscious of all possible pre-analytical variables as a prerequisite of any proteomic study.     

Application of the Stockholm Hierarchy to Defining the Quality of Reference Intervals and Clinical Decision Limits

The Stockholm Hierarchy is a professional consensus created to define the preferred approaches to defining analytical quality. The quality of a laboratory measurement can also be classified by the quality of the limits that the value is compared with, namely reference interval limits and clinical decision limits. At the highest level in the hierarchy would be placed clinical decision limits based on clinical outcome studies. The second level would include both formal reference interval studies (studies of intra and inter-individual variations) and clinical decision limits based on clinician survey. While these approaches are commonly used, they require a lot of resources to define accurately. Placing laboratory experts on the third level would suggest that although they can also define reference intervals by consensus, theirs aren’t as well regarded as clinician defined limits which drive clinical behaviour. Ideally both analytical and clinical considerations should be made, with clinicians and laboratorians both having important information to consider. The fourth level of reference intervals would be for those defined by survey or by regulatory authorities because of the focus on what is commonly achieved rather than what is necessarily correct. Finally, laboratorians know that adopting reference limits from kit inserts or textbook publications is problematic because both methodological issues and reference populations are often not the same as their own. This approach would rank fifth and last. When considering which so called ‘common’ or ‘harmonised reference intervals’ to adopt, both these characteristics and the quality of individual studies need to be assessed. Finally, we should also be aware that reference intervals describe health and physiology while clinical decision limits focus on disease and pathology, and unless we understand and consider the two corresponding issues of test specificity and test sensitivity, we cannot assure the quality of the limits that we report.     

Pre-analytical and biological variability in circulating interleukin 6 in healthy subjects and patients with rheumatoid arthritis.

Interleukin (IL)-6, a key player in the inflammatory response, may be a useful biomarker in rheumatoid arthritis (RA). The aim was to determine analytical variability, a reference interval in healthy subjects, and long- and short-term variation in serum and plasma IL-6 in healthy subjects and RA patients. An enzyme-linked immunosorbent assay from R&D was used for determination of serum and plasma IL-6. The IL-6 concentration did not depend on the type of anticoagulant used or the 3-h time delay between sampling and processing or repeated freeze-thaw cycles. The median plasma and serum IL-6 in 318 healthy subjects were 1.3 pg ml(-1) (range 0.33-26) and 1.4 pg ml(-1) (range 0.25-23), respectively. The median coefficient of variation in plasma IL-6 in 27 healthy subjects during 1 month, and repeated after 6 and 12 months were 27%, 31% and 26%, respectively. No significant long-term changes were observed in serum IL-6 over a 3-year period (14%, p = 0.33). Exercise (cycling) increased serum IL-6 in healthy subjects but not in RA patients. In conclusion, circulating IL-6 is stable regarding sample handling and shows little variation over time. Changes in IL-6 concentrations > 60% (2 times the biological variation) are likely to reflect changes in disease activity and not only pre-analytical or normal biological variability.     

Biological rhythms of biochemical serum parameters in a Brazilian population: a three-year study

A marked decrease in analytical and post-analytical variability has been achieved in clinical laboratories by the use of automated analytical systems. Current studies are now focused on the origin of pre-analytical variability, such as that due to intra-individual differences and biological rhythms. The objective of this work was to evaluate the occurrence of biological rhythms in several biochemical serum parameters in a Brazilian population. A retrospective study (1996 to 1998) was carried out to collect the test results within the reference intervals of adults, from 21 to 50 yr of age (average age of 36 yr) attending the outpatient clinics of the Teaching Hospital at the University of Campinas, S?o Paulo, Brazil. The reference sample was 52.9% male and 47.1% female and encompassed 15,036 calcium, 7,478 phosphorus, 53,641 urea, 58,315 creatinine and 6,433 uric acid determinations (140,903 in total). Significant annual rhythms were detected in serum calcium (p相似文献   

Pre-analytical and biological variability in circulating interleukin 6 in healthy subjects and patients with rheumatoid arthritis

Abstract

Interleukin (IL)-6, a key player in the inflammatory response, may be a useful biomarker in rheumatoid arthritis (RA). The aim was to determine analytical variability, a reference interval in healthy subjects, and long- and short-term variation in serum and plasma IL-6 in healthy subjects and RA patients. An enzyme-linked immunosorbent assay from R&;D was used for determination of serum and plasma IL-6. The IL-6 concentration did not depend on the type of anticoagulant used or the 3-h time delay between sampling and processing or repeated freeze–thaw cycles. The median plasma and serum IL-6 in 318 healthy subjects were 1.3 pg ml^?1 (range 0.33–26) and 1.4 pg ml^?1 (range 0.25–23), respectively. The median coefficient of variation in plasma IL-6 in 27 healthy subjects during 1 month, and repeated after 6 and 12 months were 27%, 31% and 26%, respectively. No significant long-term changes were observed in serum IL-6 over a 3-year period (14%, p=0.33). Exercise (cycling) increased serum IL-6 in healthy subjects but not in RA patients. In conclusion, circulating IL-6 is stable regarding sample handling and shows little variation over time. Changes in IL-6 concentrations >60% (2 times the biological variation) are likely to reflect changes in disease activity and not only pre-analytical or normal biological variability.     

Urine profiling by SELDI-TOF/MS: monitoring of the critical steps in sample collection, handling and analysis

The topic of this study is the impact of several pre-analytical and analytical variables on proteomic profiling of human urine by surface enhanced laser desorption/ionization time of flight-mass spectrometry (SELDI-TOF-MS) in healthy subjects. Urine storage at room temperature caused a progressive degradation of proteins, which was prevented by the addition of protease inhibitors only up to 2 h from the collection. The timing of collection over the day had only a minor impact on protein profile, although influencing the intensity of peaks. Repeated freeze/thaw cycles (up to five) did not affect either the number or the intensity of the peaks. A comparison of the protein profile from eight different healthy individuals showed fairly consistent inter-subject similarities, along with between-subject differences, which were markedly dependent on the sex and the type of ProteinChip array used. The addition of a variety of denaturing agents improved the quality of the spectra with all the chips tested (CM10, Q10 and H50), but not with the copper-coated IMAC-30 chip. Finally, SPA matrix allowed to achieve a better performance of SELDI-TOF/MS spectrum, as compared with CHCA, regardless of the ProteinChip array used and even in the low m/z range (2500-10,000). In conclusion, we suggest that a careful choice of a number of pre-analytical and analytical conditions is required to accomplish and define a unifying protocol for the analysis of human urine by SELDI-TOF/MS, in physiological and in pathological states.     

HPLC analysis of ADMA and other methylated L-arginine analogs in biological fluids

Post-translational methylation of arginine residues in proteins leads to generation of N(G)-monomethylarginine (MMA) and both symmetric and asymmetric dimethylarginine (SDMA and ADMA), that are released into the cytosol upon proteolysis. Both MMA and ADMA are inhibitors of nitric oxide synthase and especially elevated levels of ADMA are associated with endothelial dysfunction and cardiovascular disease. Plasma concentrations of ADMA and SDMA are very low, typically between 0.3 and 0.8 microM, making their quantification by HPLC an analytical challenge. Sample preparation usually involves a cleanup step by solid-phase extraction on cation-exchange columns followed by derivatization of amino acids into fluorescent adducts. Because ADMA and SDMA concentrations in healthy subjects show a very narrow distribution, with a between-subject variability of 13% for ADMA and 19% for SDMA, very low imprecision is an essential assay feature. Procedures for sample cleanup, derivatization, and chromatographic separation of arginine and its methylated analogs are the main topics of this review. In addition, important aspects of method validation, pre-analytical factors, and reference values are discussed.     

Pre-analytical Factors Influence Accuracy of Urine Spot Iodine Assessment in Epidemiological Surveys

Urinary iodine concentration (UIC) is commonly used to assess iodine status of subjects in epidemiological surveys. As pre-analytical factors are an important source of measurement error and studies about this phase are scarce, our objective was to assess the influence of urine sampling conditions on UIC, i.e., whether the child ate breakfast or not, urine void rank of the day, and time span between last meal and urine collection. A nationwide, two-stage, stratified, cross-sectional study including 1560 children (6–12 years) was performed in 2012. UIC was determined by the Sandell-Kolthoff method. Pre-analytical factors were assessed from children’s mothers by using a questionnaire. Association between iodine status and pre-analytical factors were adjusted for one another and socio-economic characteristics by multivariate linear and multinomial regression models (RPR: relative prevalence ratios). Skipping breakfast prior to morning urine sampling decreased UIC by 40 to 50 μg/L and the proportion of UIC?<?100 μg/L was higher among children having those skipped breakfast (RPR?=?3.2[1.0–10.4]). In unadjusted analyses, UIC was less among children sampled more than 5 h from their last meal. UIC decreased with rank of urine void (e.g., first vs. second, P?<?0.001); also, the proportion of UIC?<?100 μg/L was greater among 4th rank samples (vs. second RPR?=?2.1[1.1–4.0]). Subjects’ breakfast status and urine void rank should be accounted for when assessing iodine status. Providing recommendations to standardize pre-analytical factors is a key step toward improving accuracy and comparability of survey results for assessing iodine status from spot urine samples. These recommendations have to be evaluated by future research.     

Simultaneous analysis of cerebrospinal fluid biomarkers using microsphere-based xMAP multiplex technology for early detection of Alzheimer's disease

The xMAP-Luminex multiplex platform for measurement of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers using Innogenetics AlzBio3 immunoassay reagents that are for research use only has been shown to be an effective tool for early detection of an AD-like biomarker signature based on concentrations of CSF Aβ(1-42), t-tau and p-tau(181). Among the several advantages of the xMAP-Luminex platform for AD CSF biomarkers are: a wide dynamic range of ready-to-use calibrators, time savings for the simultaneous analyses of three biomarkers in one analytical run, reduction of human error, potential of reduced cost of reagents, and a modest reduction of sample volume as compared to conventional enzyme-linked immunosorbant assay (ELISA) methodology. Recent clinical studies support the use of CSF Aβ(1-42), t-tau and p-tau(181) measurement using the xMAP-Luminex platform for the early detection of AD pathology in cognitively normal individuals, and for prediction of progression to AD dementia in subjects with mild cognitive impairment (MCI). Studies that have shown the prediction of risk for progression to AD dementia by MCI patients provide the basis for the use of CSF Aβ(1-42), t-tau and p-tau(181) testing to assign risk for progression in patients enrolled in therapeutic trials. Furthermore emerging study data suggest that these pathologic changes occur in cognitively normal subjects 20 or more years before the onset of clinically detectable memory changes thus providing an objective measurement for use in the assessment of treatment effects in primary treatment trials. However, numerous previous ELISA and Luminex-based multiplex studies reported a wide range of absolute values of CSF Aβ(1-42), t-tau and p-tau(181) indicative of substantial inter-laboratory variability as well as varying degrees of intra-laboratory imprecision. In order to address these issues a recent inter-laboratory investigation that included a common set of CSF pool aliquots from controls as well as AD patients over a range of normal and pathological Aβ(1-42), t-tau and p-tau(181) values as well as agreed-on standard operating procedures (SOPs) assessed the reproducibility of the multiplex methodology and Innogenetics AlzBio3 immunoassay reagents. This study showed within-center precision values of 5% to a little more than 10% and good inter-laboratory %CV values (10-20%). There are several likely factors influencing the variability of CSF Aβ(1-42), t-tau and p-tau(181) measurements. In this review, we describe the pre-analytical, analytical and post-analytical sources of variability including sources inherent to kits, and describe procedures to decrease the variability. A CSF AD biomarker Quality Control program has been established and funded by the Alzheimer Association, and global efforts are underway to further define optimal pre-analytical SOPs and best practices for the methodologies available or in development including plans for production of a standard reference material that could provide for a common standard against which manufacturers of immunoassay kits would assign calibration standard values.     

New procedure to reduce the time and cost of broncho-pulmonary specimen management using the Previ Isola® automated inoculation system

The microbiological diagnosis of respiratory tract infections requires serial manual dilutions of the clinical specimen before agar plate inoculation, disrupting the workflow in bacteriology clinical laboratories. Automated plating instrument systems have been designed to increase the speed, reproducibility and safety of this inoculating step; nevertheless, data concerning respiratory specimens are lacking. We tested a specific procedure that uses the Previ Isola® (bioMérieux, Craponne, France) to inoculate with broncho-pulmonary specimens (BPS). A total of 350 BPS from a university-affiliated hospital were managed in parallel using the manual reference and the automated methods (expectoration: 75; broncho-alveolar lavage: 68; tracheal aspiration: 17; protected distal sample: 190). A specific enumeration reading grid, a pre-liquefaction step and a fluidity test, performed before the inoculation, were designed for the automated method. The qualitative (i.e., the number of specimens yielding a bacterial count greater than the clinical threshold) and quantitative (i.e., the discrepancy within a 0.5 log value) concordances were 100% and 98.2%, respectively. The slimmest subgroup of expectorations could not be managed by the automated method (8%, 6/75). The technical time and cost savings (i.e., number of consumed plates) reached 50%. Additional studies are required for specific populations, such as cystic fibrosis specimens and associated bacterial variants. An automated decapper should be implemented to increase the biosafety of the process. The PREVI Isola® adapted procedure is a time- and cost-saving method for broncho-pulmonary specimen processing.     

New methodology for computer-aided modelling of biomolecular structure and dynamics. 1. Non-cyclic structures

A general methodology is proposed for the conformational modelling of biomolecular systems. The approach allows one: (i) to describe the system under investigation by an arbitrary set of internal variables, i.e., torsion angles, bond angles, and bond lengths; it offers a possibility to pass from the free structure to a completely fixed one with the number of variables from 3N to zero, respectively, where N is the number of atoms; (ii) to consider both, a single molecule and a complex of many molecules, (e.g., proteins, water, ligands, etc.) in terms of one universal model; (iii) to study the dynamics of the system using explicit analytical Lagrangian equations of motion, thus opening up possibilities for investigations of slow concerted motions such as domain oscillations in proteins etc.; (iv) to calculate the partial derivatives of various functions of conformation, e.g., the conformational energy or external constraints imposed, using a standard efficient procedure regardless of the variables and the structure of the system. The approach is meant to be used in various investigations concerning the conformations and dynamics of biomacromolecules.     

New Methodology for Computer-Aided Modelling of Biomolecular Structure and Dynamics 1. Non-Cyclic Structures

Abstract

A general methodology is proposed for the conformational modelling of biomolecular systems. The approach allows one: (i) to describe the system under investigation by an arbitrary set of internal variables, i.e., torsion angles, bond angles, and bond lengths; it offers a possibility to pass from the free structure to a completely fixed one with the number of variables from 3N to zero, respectively, where N is the number of atoms; (ii) to consider both, a single molecule and a complex of many molecules, (e.g., proteins, water, ligands, etc.) in terms of one universal model; (iii) to study the dynamics of the system using explicit analytical Lagrangian equations of motion, thus opening up possibilities for investigations of slow concerted motions such as domain oscillations in proteins etc.; (iv) to calculate the partial derivatives of various functions of conformation, e.g., the conformatinal energy or external constraints imposed, using a standard efficient procedure regardless of the variables and the structure of the system. The approach is meant to be used in various investigations concerning the conformations and dynamics of biomacromolecules.     

Plasma proteomics of pancreatic cancer patients by multi-dimensional liquid chromatography and two-dimensional difference gel electrophoresis (2D-DIGE): up-regulation of leucine-rich alpha-2-glycoprotein in pancreatic cancer

Mass spectrometry-based approaches are the reference techniques for the determination of nitrite and nitrate in plasma and serum. However, due to their simplicity and rapidity, assays based on the Griess reaction or HPLC are generally used in clinical studies, but they generate diverging values for nitrite/nitrate concentration. In this study, particular attention is paid to the optimization of the deproteinization procedure for plasma and serum samples prior to nitrite/nitrate analysis by an enzymatic batch Griess assay, HPLC and GC-MS. A method is reported to verify completeness of deproteinization and to correct for nonspecific contribution to the absorbance of the diazo dye at 540 nm. With the application of such optimized procedures, we were able to significantly improve the correlation between Griess and HPLC method or the GC-MS technique for nitrite+nitrate concentrations in human serum and plasma. Despite remaining potentially interfering pre-analytical and analytical factors, the procedures reported in the present study may be helpful in a critical evaluation of limits and possibilities of the enzymatic batch Griess assay as a large-scale method for nitrite/nitrate determination in human serum in clinical studies.     

Dried Blood Spots - Preparing and Processing for Use in Immunoassays and in Molecular Techniques

The idea of collecting blood on a paper card and subsequently using the dried blood spots (DBS) for diagnostic purposes originated a century ago. Since then, DBS testing for decades has remained predominantly focused on the diagnosis of infectious diseases especially in resource-limited settings or the systematic screening of newborns for inherited metabolic disorders and only recently have a variety of new and innovative DBS applications begun to emerge. For many years, pre-analytical variables were only inappropriately considered in the field of DBS testing and even today, with the exception of newborn screening, the entire pre-analytical phase, which comprises the preparation and processing of DBS for their final analysis has not been standardized. Given this background, a comprehensive step-by-step protocol, which covers al the essential phases, is proposed, i.e., collection of blood; preparation of blood spots; drying of blood spots; storage and transportation of DBS; elution of DBS, and finally analyses of DBS eluates. The effectiveness of this protocol was first evaluated with 1,762 coupled serum/DBS pairs for detecting markers of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus infections on an automated analytical platform. In a second step, the protocol was utilized during a pilot study, which was conducted on active drug users in the German cities of Berlin and Essen.     

Clinical Utility of Insulin-Like Growth Factor 1 and 2; Determination by High Resolution Mass Spectrometry

Measurement of insulin-like growth factor-1 (IGF-I) has utility for the diagnosis and management of growth disorders, but inter-assay comparison of results has been complicated by a multitude of reference standards, antibodies, detection methods, and pre-analytical preparation strategies. We developed a quantitative LC-MS method for intact IGF-I, which has advantages in throughput and complexity when compared to mass spectrometric approaches that rely on stable isotope dilution analysis of tryptic peptides. Since the method makes use of full-scan data, the assay was easily extended to provide quantitative measurement of IGF-II using the same assay protocol. The validated LC-MS assay for IGF-I and IGF-II provides accurate results across the pediatric and adult reference range and is suitable for clinical use.     

Considerations for Group Testing: A Practical Approach for the Clinical Laboratory

Group testing, also known as pooled sample testing, was first proposed by Robert Dorfman in 1943. While sample pooling has been widely practiced in blood-banking, it is traditionally seen as anathema for clinical laboratories. However, the ongoing COVID-19 pandemic has re-ignited interest for group testing among clinical laboratories to mitigate supply shortages. We propose five criteria to assess the suitability of an analyte for pooled sample testing in general and outline a practical approach that a clinical laboratory may use to implement pooled testing for SARS-CoV-2 PCR testing. The five criteria we propose are: (1) the analyte concentrations in the diseased persons should be at least one order of magnitude (10 times) higher than in healthy persons; (2) sample dilution should not overly reduce clinical sensitivity; (3) the current prevalence must be sufficiently low for the number of samples pooled for the specific protocol; (4) there is no requirement for a fast turnaround time; and (5) there is an imperative need for resource rationing to maximise public health outcomes. The five key steps we suggest for a successful implementation are: (1) determination of when pooling takes place (pre-pre analytical, pre-analytical, analytical); (2) validation of the pooling protocol; (3) ensuring an adequate infrastructure and archival system; (4) configuration of the laboratory information system; and (5) staff training. While pool testing is not a panacea to overcome reagent shortage, it may allow broader access to testing but at the cost of reduction in sensitivity and increased turnaround time.     

Quantification of mitochondrial DNA copy number: Pre-analytical factors

Mitochondrial DNA (mtDNA) content is important for understanding many cellular processes. Several pre-analytical factors, from sample collection to DNA extraction can affect measurement of mtDNA copy number. In the present study, whole blood samples yielded a higher mtDNA copy number than buffy coat samples. mtDNA content is affected by the cell separation method used and the time between blood withdrawal and cell separation. Thus, reference values must be established with the same type of sample. As to the DNA isolation and purification method, the manual phenol method can give randomly false high values. The QIAamp DNA Mini Kit provided the most highly reproducible mtDNA/nDNA yield.     

Simultaneous analysis of multiple aminothiols in human plasma by high performance liquid chromatography with fluorescence detection

Aminothiols serve numerous vital functions in biochemistry, including detoxification and regulation of cellular metabolism, enzymatic activity, and protein trafficking and degradation. Plasma aminothiol concentrations are frequently measured for clinical and translational research investigating oxidative stress, and for routine clinical diagnosis and monitoring of vascular injury. Although a variety of techniques are available to measure aminothiol concentrations in plasma, high performance liquid chromatography with fluorescence detection (HPLC–FD) is the most widely used. This review summarizes HPLC–FD methods, including pre-analytical considerations, procedures for sample reduction, derivatization, and chromatographic separation of the primary biological aminothiols cysteine, homocysteine, cysteinylglycine, and glutathione in human plasma.