C-peptide is an increasingly used and established marker for beta cell function by assessing endogenous insulin secretion. Accurate and comparable C-peptide measurements are needed in clinical practice and research studies. For example, to calculate HOMA-indices, the C-peptide/glucose ratio, and the classification of recently published novel subgroups of diabetes and prediabetes have used C-peptide measurements. Although the process for standardization of C-peptide measurements is advanced, its full implementation is still missing; therefore, the current status of the comparability of C-peptide measurements using different immunoassays is unclear. Here we compared five widely used C-peptide immunoassays on different analyzers (Abbott ALINITY i, DiaSorin Liaison XL, Roche Cobas e411, Siemens Healthineers ADVIA Centaur XPT, and Immulite 2000 XPi) using serum samples covering the clinically relevant C-peptide concentration range. Although all investigated immunoassays are traceable to the international reference reagent for C-peptide (NIBSC code: 84/510), results of C-peptide measurements showed significant differences between analyzers in the entire concentration range, especially with increasing C-peptide concentrations. The mean bias was largest (36.6%) between results of the immunoassays by Roche and Siemens Healthineers (ADVIA Centaur XPT), and both assays revealed large discrepancies compared to immunoassays by Abbott, DiaSorin, and Siemens Healthineers (Immulite 2000 XPi). In contrast, the three latter assays showed similar C-peptide results (mean bias: 2.3% to 4.2%). Consequently, C-peptide discrepancies might affect clinical diagnosis and the interpretation of study results. Therefore, there is an urgent need to implement and finalize the standardization process of C-peptide measurements to improve patient care and the comparability of research studies.
Clinical Relevance , Humans , C-Peptide , Immunoassay , Reference Standards
The EU In-Vitro Diagnostic Device Regulation (IVDR) aims for transparent risk-and purpose-based validation of diagnostic devices, traceability of results to uniquely identified devices, and post-market surveillance. The IVDR regulates design, manufacture and putting into use of devices, but not medical services using these devices. In the absence of suitable commercial devices, the laboratory can resort to laboratory-developed tests (LDT) for in-house use. Documentary obligations (IVDR Art 5.5), the performance and safety specifications of ANNEX I, and development and manufacture under an ISO 15189-equivalent quality system apply. LDTs serve specific clinical needs, often for low volume niche applications, or correspond to the translational phase of new tests and treatments, often extremely relevant for patient care. As some commercial tests may disappear with the IVDR roll-out, many will require urgent LDT replacement. The workload will also depend on which modifications to commercial tests turns them into an LDT, and on how national legislators and competent authorities (CA) will handle new competences and responsibilities. We discuss appropriate interpretation of ISO 15189 to cover IVDR requirements. Selected cases illustrate LDT implementation covering medical needs with commensurate management of risk emanating from intended use and/or design of devices. Unintended collateral damage of the IVDR comprises loss of non-profitable niche applications, increases of costs and wasted resources, and migration of innovative research to more cost-efficient environments. Taking into account local specifics, the legislative framework should reduce the burden on and associated opportunity costs for the health care system, by making diligent use of existing frameworks.
Clinical Laboratory Services , Reagent Kits, Diagnostic , Humans , Reagent Kits, Diagnostic/standards , European Union , Clinical Laboratory Services/legislation & jurisprudence
The background to this debate is now well-known: an EU policy decision to tighten controls on the devices and diagnostics sector led to the adoption of a regulation in 2017 with a schedule for implementation over coming years - a timetable extended still further by last-minute legislation in early 2022, to provide the sector and regulators with more time to adapt to the changes. Discussions among experts organised in April by the European Alliance for Personalized Medicine (EAPM) exposed continuing challenges that cannot be fully resolved by the recent deferral of implementation deadlines. One salient problem is that there is little awareness of the In Vitro Diagnostic Regulation (IVDR) across Europe, and only limited awareness of the different structures of national systems involved in implementing IVDR, with consequent risks for patient and consumer access to in vitro diagnostics (IVDs). The tentative conclusion from these consultations is that despite a will across the sector to seek workable solutions, the obstacles remain formidable, and the potential solutions so far proposed remain more a matter of aspirations than of clear pathways.
Precision Medicine , Humans , Europe
In vitro diagnostics (IVD) testing is a powerful tool for medical diagnosis, and patients' safety is guaranteed by a complex system of personnel qualification of the specialist in laboratory medicine, of process control, and legal restrictions in healthcare, most of them under national regulation. Direct-to-consumer laboratory testing (DTCT) is testing ordered by the consumer and performed either by the consumer at home or analysis of self-collected samples in a laboratory. However, since DTCT are not always subject to effective competent authority oversight, DTCT may pose risks to lay persons using and relying on it for healthcare decision-making. Laboratory medicine specialists should be very cautious when new DTCTs are introduced. As qualified professionals, they should feel obliged to warn and educate patients and the public about the risks of inappropriate and harmful DTCT.
Delivery of Health Care , Laboratories , Humans
PURPOSE: Thermal inhalation injury is a common, life-threatening problem in burned patients. Whether or not this single event of damage to the oral integrity causes long term health problems is yet to be examined. MATERIAL AND METHODS: All consecutive burn patients between 2014 and 2017 of Marienhospital Stuttgart (MHS), Germany, with at least 10% of burned skin surface were included and compared. The Periodontal Screening Index as well as Vitamin D levels were examined. Vitamin D has been suspected to contribute to the genesis of periodontitis. Risk factors and subjective oral life quality were prompted. RESULTS: We included a total of 32 patients, 15 of which had an inhalation injury in their medical history. Risk factors were examined via Renatus' questionnaire. While risk factors were equally distributed in both groups we saw a remarkable difference in periodontal integrity, with the Periodontal Screening Index (PSI) per sextant differing drastically (with inhalation injury: 2.40, without inhalation injury: 1.10, p < 0.001). Patients with an inhalation injury had a mean of 5.2 out of 6 possible sextants with a pathologic PSI (with the median being 6/6), while patients without an inhalation injury had a mean of 1.83 out of 6 (median: 1/6), p < 0.001. The oral health impact profile showed a difference as well, albeit without statistical significance (with inhalation injury: median = 11, without: median = 3.5, p = 0.414). A correlation between Serum Vitamin D levels and periodontal integrity could not be seen in this group. CONCLUSION: Inhalation injury is a possible cause for periodontitis and hence impacts the quality of life of burned patients.
Burns, Inhalation , Burns , Lung Injury , Periodontitis , Burns/complications , Burns/pathology , Humans , Quality of Life , Temperature , Vitamin D
Laboratory medicine in the European Union is at the dawn of a regulatory revolution as it reaches the end of the transition from IVDD 98/79/EC (https://eur-lex.eur-opa.eu/legal-content/EN/TXT/?uri=CELEX%3A31998L0079&qid=1628781352814) to IVDR 2017/746 https://eur-lex.europa.eu/eli/reg/2017/746. Without amendments and contingency plans, implementation of the IVDR in May 2022 will lead the healthcare sector into uncharted waters due to unpreparedness of the EU regulatory infrastructure. Prospective risk analyses were not made by the European Commission, and if nothing happens it can be anticipated that the consequences will impact all stakeholders of the medical test pipeline, may seriously harm patients and may prevent caregivers from making appropriate clinical decisions due to non-availability of medical tests. Finally, it also may discourage manufacturers and academia from developing specialty tests, thereby hampering innovation in medical diagnostic care. We hereby inform laboratory professionals about the imminent diagnostic collapse using testimonies from representative stakeholders of the diagnostic supply chain and from academia developing innovative in-house tests in domains of unmet clinical needs. Steps taken by the EFLM Task Force on European Regulatory Affairs, under the umbrella of the Biomedical Alliance in Europe, will be highlighted, as well as the search for solutions through dialogue with the European Commission. Although we recognize that the IVDR promotes positive goals such as increased clinical evidence, surveillance, and transparency, we need to ensure that the capabilities of the diagnostic sector are not damaged by infrastructural unpreparedness, while at the same time being forced to submit to a growing bureaucratic and unsupportive structure that will not support its "droit d'exister".
Direct to consumer laboratory testing has the potential for self-empowerment of patients. However, the Direct to consumer laboratory testing (DTCT) uses loopholes which are related to the particular situation of healthcare: While advertisements and claims for medical usefulness are very high regulated in healthcare, essentially no regulations safeguard the consumers in DTCT. The same is true for the quality of testing services since quality regulations are only mandatory in healthcare. Another problem is the lack of medical interpretation of test results. Besides being very risky for the consumers, healthcare professionals relying on test results obtained by DTCT must be aware about the risks of these data.
Patients with impaired renal function are at high risk for morbidity and mortality. Chronic kidney disease (CKD) even in the early stages can be associated with significant side effects of drug therapy, longer length of stay, and high costs. Correct assessment of renal function in the hospital is important to detect CKD, to avoid further damage to the kidneys, and to optimize pharmacological therapy. Current protocols for renal function testing in drug dosing are only creatinine based, are not robust enough, and can wrongly classify certain patients. Goal of our simulation study is to optimize noninvasive renal function estimates and to allow for optimal dosing of pharmacological treatment without further renal damage. Co-reporting of creatinine- and of cystatin C-derived estimated glomerular filtration rates (eGFR) allows a personalized approach for patients with large discrepancies in eGFR and it enabled us in detecting patients at high risk for side effects due to incorrect drug dosing. This approach might be highly effective for patients as well as for clinicians. In addition, we simulated the efficiency by estimating savings for the hospital administration and the payor with a benefit cost ratio of 58 to 1.
Background: Complicated diverticulitis of the sigmoid colon typically is treated by resection after initial antibiotic treatment. Third-generation cephalosporins are the drugs of choice but are not effective against enterococci and can induce colonic colonization by Enterococcus faecium within hours. Infections caused by enterococci, especially E. faecium, are difficult to treat but should be considered in the strategic treatment planning of hospital-acquired peritonitis (e.g., anastomotic leakage), especially in immunocompromised patients. Methods: To determine whether the duration of pre-operative ceftriaxone treatment in complicated diverticulitis increases the incidence of intra-abdominal E. faecium detection, we analyzed all patients operated on for diverticulitis of the sigmoid colon in our department between 2008 and 2016. Results: Analyzing 516 resections performed for complicated diverticulitis, we found that E. faecium generally was detected intra-abdominally more often in the group that underwent longer pre-operative ceftriaxone treatment (≥ 4 days). During primary resection, E. faecium was detected in 2.7%, 11.1%, and 37.0% cases in the group undergoing immediate operation, 1-3 days of antibiotic treatment, and ≥4 days of antibiotic treatment, respectively. Enterococcus faecium was detected in 0, 25.0%, and 70.6% of surgical revisions and 28.6%, 14.3%, and 56.0%, respectively, of incisional surgical site infections with identified pathogens. A multivariable analysis discovered anastomotic leakage and antibiotic treatment lasting ≥4 days to be independent risk factors for intra-abdominal isolation of E. faecium. Conclusion: A ceftriaxone treatment ≥4 days led to a higher incidence of intra-abdominal E. faecium. Our data further suggested that empiric coverage of E. faecium in the treatment of hospital-acquired peritonitis could be beneficial after a long duration of ceftriaxone treatment.
Diverticulitis , Enterococcus faecium , Peritonitis , Ceftriaxone/therapeutic use , Humans , Incidence , Peritonitis/drug therapy , Peritonitis/epidemiology
Management of diabetes is a challenge starting in the pre-analytical phase with selecting the most appropriate glycolysis inhibitor. Study goal was to calculate the impact of tubes with different glycolysis inhibitors on the classification of the glycemic control of 157,415 consecutive hospital patients according to current WHO diabetes criteria. METHODS: Glucose and lactate were measured in parallel in samples from 68 healthy subjects collected and stored in different sample tubes from Sarstedt and Greiner. Bias to baseline conditions (fluoride heparin (FH) tubes, centrifugation within 1â¯h) was determined. RESULTS: In baseline samples, glucose concentration in fluoride/EDTA/citrate (FC) plasma was ~13% higher and lactate concentration ~20% lower compared to FH, fluoride oxalate, and fluoride EDTA plasma, and in serum. Glucose recovery after storage up to 48â¯h was 99-101% in the different tubes, but the effectiveness of glycolysis inhibition by FC was inconsistent. Based on the observed mean bias of 12% when FC tubes are used, we estimate an increase of 48.4-55.8% in the frequency of patients with impaired glucose levels using current WHO criteria. CONCLUSION: Using current established decision limits, the number of patients with impaired glucose levels in the hospital would increase substantially with a strong impact on patient treatment and consumption of resources. The unpredictable failure of glycolysis inhibition in FC tubes does not allow to adjust the decision limits by a fixed factor. In the absence of prospective outcome studies with FC tubes, we recommend to measure glucose in samples containing FH.
Verification of laboratory test results represents the last opportunity to identify errors before they become part of the electronic medical record. Manual verification of test results places significant reliance on the experience and attentiveness of individual observers to identify errors and is vulnerable to errors through omission and neglect. Peer-reviewed publications have documented gains in process efficiency and quality improvement by use of middleware or laboratory information systems to autoverify test results based on pre-defined acceptability criteria. This review evaluates the acceptability of autoverification (AV) as a safe and reliable alternative to total manual review of laboratory test results. AV schemes developed in accordance with international guidelines and standards are applied throughout the laboratory. Careful design of AV systems involves using multidisciplinary teams to develop test-specific decision algorithms, to assist with programming, to verify programming, and validate programmed algorithms prior to use in evaluation of patient test result profiles. Development of test specific decision algorithms makes use of criteria based on instrument messages and flags, quality control status, result limit checks, delta checks, critical values, consistency checks, and patient-related clinical information. Monitoring of the performance of AV parameters, and regular audits of the AV system integrity is recommended in both the literature and guidelines. The potential for gains to process efficiency, error detection and patient safety, through adoption of AV as part of a laboratories quality assurance tool-case, is well supported in published literature.
Algorithms , Clinical Laboratory Information Systems/standards , Clinical Laboratory Services/standards , Quality Control , Humans
The role of clinical pathologists or laboratory-based physicians is being challenged on several fronts-exponential advances in technology, increasing patient autonomy exercised in the right to directly request tests and the use of non-medical specialists as substitutes. In response, clinical pathologists have focused their energies on the pre-analytical and postanalytical phases of Laboratory Medicine thus emphasising their essential role in individualised medical interpretation of complex laboratory results. Across the European Union, the role of medical doctors is enshrined in the Medical Act. This paper highlights the relevance of this act to patient welfare and the need to strengthen training programmes to prevent an erosion in the quality of Laboratory Medicine provided to patients and their physicians.
Pathology, Clinical , Personal Autonomy , Physicians , Precision Medicine , Humans , Pathology, Clinical/legislation & jurisprudence , Pathology, Clinical/standards , Precision Medicine/standards
BACKGROUND: Measurement standardization of the catalytic concentration of α-amylase in serum is based on 3 pillars: the primary reference measurement procedure (PRMP), reference laboratories, and suitable certified reference materials (CRMs). Commutability is a prerequisite when using a CRM for calibration and trueness control of routine methods or for value transfer from the PRMP to end-user calibrators of routine methods through a calibration hierarchy. METHODS: We performed a commutability study with 30 serum pools and 5 candidate reference materials (RMs) for pancreatic α-amylase using an automated version of the PRMP and 5 different routine methods. Four candidate RMs had an artificial matrix, each with a different composition, and 1 candidate RM was based on human serum. Data were analyzed according to a linear regression analysis with prediction interval as described in the Clinical and Laboratory Standards Institute guideline EP30-A and a difference in bias analysis as described in the recommendations of the IFCC Working Group on Commutability. RESULTS: The commutability profile of the 4 candidate RMs with an artificial matrix was variable. Only 1 candidate RM, with human serum albumin in the matrix, showed a good profile like that of the candidate RM based on serum. The comparison of both commutability assessment approaches indicated some differences because of inconclusive results for the difference in bias approach, suggesting a large uncertainty on the commutability assessment. CONCLUSIONS: A CRM for pancreatic amylase in an artificial matrix can be commutable for routine methods using the same substrate as the PRMP, but the matrix composition is crucial.
Pancreatic alpha-Amylases/blood , Pancreatic alpha-Amylases/standards , Humans , Reference Standards
Error methods - compared with uncertainty methods - offer simpler, more intuitive and practical procedures for calculating measurement uncertainty and conducting quality assurance in laboratory medicine. However, uncertainty methods are preferred in other fields of science as reflected by the guide to the expression of uncertainty in measurement. When laboratory results are used for supporting medical diagnoses, the total uncertainty consists only partially of analytical variation. Biological variation, pre- and postanalytical variation all need to be included. Furthermore, all components of the measuring procedure need to be taken into account. Performance specifications for diagnostic tests should include the diagnostic uncertainty of the entire testing process. Uncertainty methods may be particularly useful for this purpose but have yet to show their strength in laboratory medicine. The purpose of this paper is to elucidate the pros and cons of error and uncertainty methods as groundwork for future consensus on their use in practical performance specifications. Error and uncertainty methods are complementary when evaluating measurement data.
Clinical Laboratory Techniques/standards , Medical Errors , Uncertainty , Bias , Delphi Technique , Humans , Reproducibility of Results
BACKGROUND: Pyroglutamylation of truncated Aß peptides, which is catalysed by enzyme glutaminyl cyclase (QC), generates pE-Aß species with enhanced aggregation propensities and resistance to most amino-peptidases and endo-peptidases. pE-Aß species have been identified as major constituents of Aß plaques and reduction of pE-Aß species is associated with improvement of cognitive tasks in animal models of Alzheimer's disease (AD). Pharmacological inhibition of QC has thus emerged as a promising therapeutic approach for AD. Here, we question whether cerebrospinal fluid (CSF) QC enzymatic activity differs between AD patients and controls and whether inflammatory or angiogenesis mediators, some of which are potential QC substrates, and/or Aß peptides may serve as pharmacodynamic read-outs for QC inhibition. METHODS: QC activity, Aß peptides and inflammatory or angiogenesis mediators were measured in CSF of a clinically well-characterized cohort of 20 mild AD patients, 20 moderate AD patients and 20 subjective memory complaints (SMC) controls. Correlation of these parameters with core diagnostic CSF AD biomarkers (Aß42, tau and p-tau) and clinical features was evaluated. RESULTS: QC activity shows a tendency to decrease with AD progression (p = 0.129). The addition of QC activity to biomarkers tau and p-tau significantly increases diagnostic power (ROC-AUCTAU = 0.878, ROC-AUCTAU&QC = 0.939 and ROC-AUCpTAU = 0.820, ROC-AUCpTAU&QC = 0.948). In AD and controls, QC activity correlates with Aß38 (r = 0.83, p < 0.0001) and Aß40 (r = 0.84, p < 0.0001), angiogenesis mediators (Flt1, Tie2, VEGFD, VCAM-1 and ICAM-1, r > 0.5, p < 0.0001) and core diagnostic biomarkers (r > 0.35, p = <0.0057). QC activity does not correlate with MMSE or ApoE genotype. CONCLUSIONS: Aß38, Aß40 and angiogenesis mediators (Flt1, Tie2, VEGFD, VCAM-1 and ICAM-1) are potential pharmacodynamic markers of QC inhibition, because their levels closely correlate with QC activity in AD patients. The addition of QC activity to core diagnostic CSF biomarkers may be of specific interest in clinical cases with discordant imaging and biochemical biomarker results.
Alzheimer Disease/cerebrospinal fluid , Alzheimer Disease/diagnosis , Aminoacyltransferases/cerebrospinal fluid , Amyloid beta-Peptides/cerebrospinal fluid , Angiogenesis Modulating Agents/cerebrospinal fluid , Aged , Aged, 80 and over , Angiogenic Proteins/cerebrospinal fluid , Biomarkers/cerebrospinal fluid , Disease Progression , Enzyme Activation , Female , Humans , Male , Middle Aged , Reproducibility of Results , Sensitivity and Specificity , Statistics as Topic
Performance criteria should be a challenge for the laboratories to improve their quality. In countries with mandatory proficiency testing, the definition of performance criteria is a particular issue. If the definition of performance criteria is mandated from the regulatory bodies to medico-scientific institutions, scientific approaches (i.e., based on biological variation), the state-of-the-art approach (i.e., based on technical feasibility) as well as medical needs can be used to set up performance criteria such as the Richtlinie der Bundesärztekammer (RiliBÄK; Guideline of the German Medical Association on Quality Assurance in Medical Laboratory Examinations) in Germany. The experiences with RiliBÄK show that these performance criteria have to be revised on an ongoing basis.
Clinical Laboratory Techniques/standards , Consensus , Germany , Guidelines as Topic , Quality Control
BACKGROUND: Tacrolimus (TAC) is a post-transplantation immunosuppressant drug used in patients for whom careful monitoring of TAC concentration is essential. A new semi-automated immunoassay for TAC measurement, the Elecsys Tacrolimus assay, is available and has been assessed in a multi-center evaluation. METHODS: Residual whole blood samples from patients undergoing TAC therapy after organ transplant were used in assay evaluation at five clinical laboratories in Europe. Experiments included imprecision according to CLSI EP5-A2 (within-run and intermediate), functional sensitivity, linearity according to CLSI EP6-A, and recovery from external quality assessment scheme (EQAS) samples. The assay was compared to LC-MS/MS used routinely at each investigational site, and to the Abbott Architect immunoassay. RESULTS: Linearity from 0.5 to 40 µg/L was observed and functional sensitivity of 0.3 µg/L (CV ≤ 20%) was determined. Within-run imprecision was ≤ 5.1% on cobas e 602 (5.1% at 1.5 µg/L) and ≤ 8.9% (8.9% at 0.8µg/L) on cobas e 411. The intermediate imprecision for TAC concentrations ≥ 6.8 µg/L was ≤ 6.5%. At lower therapeutic concentrations (to 1.5 µg/L) it was consistently ≤ 10%. Deming regression analysis of method comparison to LC-MS/MS yielded slopes of 1.07 (95%CI: 1.05/1.10) for heart transplant samples, 1.13 (95%CI: 1.09/1.16) for kidney, and 1.05 (95%CI: 1.02/1.08) for lung transplant samples. CONCLUSIONS: The Elecsys Tacrolimus assay has good linearity, functional sensitivity and intermediate imprecision and is comparable to LC-MS/MS methods. The over-all performance of ECLIA demonstrates a modern generation TAC assay that meets the demands of monitoring drug concentrations in current immunosuppressive regimens.
Automation , Immunoassay/methods , Immunosuppressive Agents/blood , Tacrolimus/blood , Humans , Limit of Detection , Reproducibility of Results
BACKGROUND: The development of new immunoassays for therapeutic drug monitoring and the adaptation of current assays on new analytical platforms has led to a plethora of different tests. This variability may influence comparability between the methods and affect interpretation of test results used for guiding drug treatment. METHODS: Comparability and imprecision of 8 immunoassays for therapeutic drug monitoring were evaluated using 6 different analyzers from 3 manufacturers. Current and previous generation analytical systems used were Architect and AxSym (Abbott Laboratories), cobas c 501 module and COBAS INTEGRA 800 analyzer (Roche Diagnostics GmbH), and Dimension Vista and Dimension Xpand (Siemens Healthcare Diagnostics Inc). Carbamazepine, digoxin, phenobarbital, phenytoin, theophylline, tobramycin, vancomycin, and valproic acid were measured using leftover routine samples. RESULTS: Good performance and comparability of the drug assays was seen on all systems for carbamazepine, phenytoin, and valproic acid except for phenytoin on the Dimension Vista. Deviations from the acceptance criteria were found with digoxin, phenobarbital, theophylline, tobramycin, and vancomycin. Despite a change of the analytical principle on the Roche systems for most drugs, the results demonstrated a very good between-system comparability of the concentration measured. Systematic deviations were found between AxSYM and ARCHITECT for digoxin, phenobarbital, and tobramycin, and between Dimension Xpand and Dimension Vista for digoxin and vancomycin. CONCLUSIONS: The study revealed differences between assays, platforms, and assay principles. Care should be taken if methods or instruments are replaced in a laboratory. Laboratories are advised to perform their own method comparison studies and to inform their customers about the effect on the therapeutic ranges in case of observed clinically significant deviations.
Drug Monitoring/methods , Immunoassay/methods , Pharmaceutical Preparations/chemistry , Humans
BACKGROUND: Cyclosporine A (CsA) is used as a posttransplantation immunosuppressant drug, and careful monitoring of CsA concentration in whole blood is essential. A new automated electrochemiluminescence immunoassay (ECLIA) for CsA measurement has been assessed in a multicenter evaluation. METHODS: Residual EDTA whole blood samples from patients undergoing CsA therapy after organ transplant were used in assay evaluation at 5 clinical laboratories in Europe. Experiments included imprecision according to CLSI EP5-A2 (within-run and intermediate), lower limit of quantification, linearity according to CLSI EP6-A, and recovery of commercial external quality control samples. In addition, comparisons to liquid chromatography-tandem mass spectrometry methods in routine use at each investigational site and to commercial chemiluminescent microparticle immunoassay and antibody-conjugated magnetic immunoassay methods were performed. RESULTS: Imprecision testing gave coefficients of variation of less than 9% in the 30-2000 mcg/L range for both within-run and intermediate imprecision. Lower limit of quantification of 6.8 mcg/L at one investigational site and 1.8 mcg/L at a second site at 20% coefficient of variation were observed. Linearity was measured over the concentration range 0-2000 mcg/L, yielding a deviation of less than ±12%. External quality control sample recovery by ECLIA was 93%-114% of LC-MS/MS sample recovery. Deming regression analysis of ECLIA method comparison to combined LC-MS/MS results yielded a slope of 1.04 [95% confidence interval (CI), 1.03-1.06] and intercept of 2.8 mcg/L (95% CI, 1.5-4.1 mcg/L). Comparison to chemiluminescent microparticle immunoassay yielded a slope of 0.87 (95% CI, 0.85-0.89) and intercept of 1.4 mcg/L (95% CI, -0.89 to 3.7 mcg/L); comparison to antibody-conjugated magnetic immunoassay yielded a slope of 0.96 (95% CI, 0.93-0.98) and intercept of -4.2 mcg/L (95% CI, -7.1 to -1.2 mcg/L). CONCLUSIONS: The data from this multicenter evaluation indicate that the new ECLIA-based cyclosporine assay is fit for its purpose, the therapeutic monitoring of CsA.
Cyclosporine/blood , Electrochemical Techniques/methods , Immunoassay/methods , Immunosuppressive Agents/blood , Automation , Drug Monitoring/methods , Humans
Cholesterol is a major constituent of the human brain, and the brain is the most cholesterol-rich organ. Numerous lipoprotein receptors and apolipoproteins are expressed in the brain. Cholesterol is tightly regulated between the major brain cells and is essential for normal brain development. The metabolism of brain cholesterol differs markedly from that of other tissues. Brain cholesterol is primarily derived by de novo synthesis and the blood brain barrier prevents the uptake of lipoprotein cholesterol from the circulation. Defects in cholesterol metabolism lead to structural and functional central nervous system diseases such as Smith-Lemli-Opitz syndrome, Niemann-Pick type C disease, and Alzheimer's disease. These diseases affect different metabolic pathways (cholesterol biosynthesis, lipid transport and lipoprotein assembly, apolipoproteins, lipoprotein receptors, and signaling molecules). We review the metabolic pathways of cholesterol in the CNS and its cell-specific and microdomain-specific interaction with other pathways such as the amyloid precursor protein and discuss potential treatment strategies as well as the effects of the widespread use of LDL cholesterol-lowering drugs on brain functions.
