Band 58, Heft 4

Background There is renewed interest in high-dose vitamin C interventions in clinical medicine due to its antioxidant properties, safe use and cost-effectiveness. Yet, randomised control trials (RCTs) employing these interventions are failing to include robust analytical methodology and proper sample handling and processing techniques. Consequently, comparisons between studies becomes impossible as there is no metrological traceability and results may be prone to pre-analytical errors. Content Through published vitamin C stability studies, method comparison papers and data from vitamin C external quality assurance programs, an assessment was made on the functionality of current methods for critically ill patient samples. Summary Data was obtained from two external quality assurance programs, two papers assessing sample stability and interlaboratory agreement and a publication on vitamin C method comparisons. A shift from spectrophotometric and enzymatic methodologies to high performance liquid chromatography (HPLC) greatly improved the variability and interlaboratory agreement. Therefore, the current analytical performance of vitamin C HPLC methodologies are acceptable for the requirements of a high-dose vitamin C RCTs. Outlook Recommendations across the total testing process of vitamin C have been provided to improve the quality of the results. The harmonisation of sample handling and processing procedures will further improve the reliability of current analytical methodologies.

The early detection of perinatal brain damage in preterm and term newborns (i.e. intraventricular hemorrhage, periventricular leukomalacia and perinatal asphyxia) still constitute an unsolved issue. To date, despite technological improvement in standard perinatal monitoring procedures, decreasing the incidence of perinatal mortality, the perinatal morbidity pattern has a flat trend. Against this background, the measurement of brain constituents could be particularly useful in the early detection of cases at risk for short-/long-term brain injury. On this scenario, the main European and US international health-care institutions promoted perinatal clinical and experimental neuroprotection research projects aimed at validating and including a panel of biomarkers in the clinical guidelines. Although this is a promising attempt, there are several limitations that do not allow biomarkers to be included in standard monitoring procedures. The main limitations are: (i) the heterogeneity of neurological complications in the perinatal period, (ii) the small cohort sizes, (iii) the lack of multicenter investigations, (iv) the different techniques for neurobiomarkers assessment, (iv) the lack of consensus for the validation of assays in biological fluids such as urine and saliva, and (v), the lack of reference curves according to measurement technique and biological fluid. In the present review we offer an up-to-date overview of the most promising developments in the use of biomarkers in the perinatal period such as calcium binding proteins (S100B protein), vasoactive agents (adrenomedullin), brain biomarkers (activin A, neuron specific enolase, glial fibrillary acidic protein, ubiquitin carboxyl-terminal hydrolase-L1) and oxidative stress markers.

Lupus anticoagulants (LAs) represent one manifestation of the clinical condition called antiphospholipid syndrome (APS) and are associated with many adverse clinical outcomes, but primarily with thrombosis and/or pregnancy morbidity. LAs are identified by laboratory testing, principally using clot-based assays based on Russell viper venom time (RVVT) and activated partial thromboplastin time (APTT) test methods. All three of the most recent guidance documents for LA testing recommend using these tests, although they vary in regard to inclusion/exclusion of other test processes. Mixing studies form part of the process of LA identification/exclusion, since in vitro LAs act like coagulation inhibitors. Mixing studies are also supported by all three LA guidance documents, but recommendations vary in regard to relative importance and placement in the LA identification/exclusion algorithm. This Point article takes the position that mixing tests are usually indicated for appropriate identification/exclusion of LAs, but can occasionally be omitted.

Mixing tests have long been a mainstay in the lupus anticoagulant (LA) testing armoury of screen, mix and confirm assays. If a sample with an elevated screening test does not evidence inhibition in the mixing test, the search for an LA is halted and a different diagnostic pathway embarked upon. Recent years have seen studies evidencing sometimes high frequencies of false-negative mixing tests with perhaps sinister implications for missed diagnoses and skewed patient management. Issues such as the dilution effect, between-reagent sensitivity and specificity differences, variability of normal pooled plasma (NPP) quality and suitability and interpretive inconsistencies all contribute to questioning the reliability of mixing tests and their pivotal place in the LA assay hierarchy. The advent of integrated testing, where phospholipid-dependence is demonstrated or excluded prior to any attempt to evidence inhibitory properties with a fallible analytical principle, provides an alternative path to LA detection. In the absence of other causes of elevated clotting times, LA assay screen and confirm discordance is sufficient to secure a laboratory diagnosis of the presence of an LA, leaving the mixing test in a supplementary yet valuable role when further diagnostic discrimination is required.

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently addressed present and future challenges in the laboratory diagnostics of atherogenic lipoproteins. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDLC), LDL cholesterol (LDLC), and calculated non-HDLC (=total – HDLC) constitute the primary lipid panel for estimating risk of atherosclerotic cardiovascular disease (ASCVD) and can be measured in the nonfasting state. LDLC is the primary target of lipid-lowering therapies. For on-treatment follow-up, LDLC shall be measured or calculated by the same method to attenuate errors in treatment decisions due to marked between-method variations. Lipoprotein(a) [Lp(a)]-cholesterol is part of measured or calculated LDLC and should be estimated at least once in all patients at risk of ASCVD, especially in those whose LDLC declines poorly upon statin treatment. Residual risk of ASCVD even under optimal LDL-lowering treatment should be also assessed by non-HDLC or apolipoprotein B (apoB), especially in patients with mild-to-moderate hypertriglyceridemia (2–10 mmol/L). Non-HDLC includes the assessment of remnant lipoprotein cholesterol and shall be reported in all standard lipid panels. Additional apoB measurement can detect elevated LDL particle (LDLP) numbers often unidentified on the basis of LDLC alone. Reference intervals of lipids, lipoproteins, and apolipoproteins are reported for European men and women aged 20–100 years. However, laboratories shall flag abnormal lipid values with reference to therapeutic decision thresholds.

Although the importance of guaranteeing a high level of preanalytical quality in routine diagnostic testing has already been largely acknowledged over the past decades, minor emphasis is currently being placed on the fact that accurate performance and standardization of many preanalytical activities are also necessary prerogatives of clinical trials. Reliable evidence exists that clear indications on how to manage the different preanalytical steps are currently lacking in many clinical trials protocols, nor have detailed authoritative documents been published or endorsed on this matter to the best of our knowledge. To fill this gap, the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for Preanalytical Phase (WG-PRE) will provide here a specific checklist for preventing preanalytical diagnostic errors in clinical trials (PREDICT), especially focused on covering the most important preanalytical aspects of blood sample management in clinical studies, and thus encompassing test selection, patient preparation, sample collection, management and storage, sample transportation, as well as specimen retrieval before testing. The WG-PRE members sincerely hope that these recommendations will provide a useful contribution for increasing the success rate in clinical trials.

Background Choosing the specimen type is the first step of the pre-analytical process. Previous reports suggested plasma as the optimal specimen for circulating tumor DNA (ctDNA) analysis. However, head-to-head comparisons between plasma and serum using platforms with high analytical sensitivity, such as droplet digital polymerase chain reaction (ddPCR), are limited, and several recent studies have supported the clinical utility of serum-derived ctDNA. This study aimed to compare the DNA profiles isolated from plasma and serum, characterize the effects of the differences between specimens on ctDNA measurement, and determine the major contributors to these differences. Methods We isolated cell-free DNA (cfDNA) from 119 matched plasma/serum samples from cancer patients and analyzed the cfDNA profiles by DNA fragment sizing. We then assessed KRAS mutations in ctDNA from matched plasma/serum using ddPCR. Results The amount of large DNA fragments was increased in serum, whereas that of cfDNA fragments (<800 bp) was similar in both specimens. ctDNA was less frequently detected in serum, and the KRAS -mutated fraction in serum was significantly lower than that in plasma. The differences in ctDNA fractions between the two specimen types correlated well with the amount of large DNA fragments and white blood cell and neutrophil counts. Conclusions Our results provided detailed insights into the differences between plasma and serum using DNA fragment sizing and ddPCR, potentially contributing to ctDNA analysis standardization. Our study also suggested that using plasma minimizes the dilution of tumor-derived DNA and optimizes the sensitivity of ctDNA analysis. So, plasma should be the preferred specimen type.

Background Serum protein electrophoresis (SPEP) is used to quantify the serum monoclonal component or M-protein, for diagnosis and monitoring of monoclonal gammopathies. Significant imprecision and inaccuracy pose challenges in reporting small M-proteins. Using therapeutic monoclonal antibody-spiked sera and a pooled beta-migrating M-protein, we aimed to assess SPEP limitations and variability across 16 laboratories in three continents. Methods Sera with normal, hypo- or hypergammaglobulinemia were spiked with daratumumab, Dara (cathodal migrating), or elotuzumab, Elo (central-gamma migrating), with concentrations from 0.125 to 10 g/L (n = 62) along with a beta-migrating sample (n = 9). Provided with total protein (reverse biuret, Siemens), laboratories blindly analyzed samples according to their SPEP and immunofixation (IFE) or immunosubtraction (ISUB) standard operating procedures. Sixteen laboratories reported the perpendicular drop (PD) method of gating the M-protein, while 10 used tangent skimming (TS). A mean percent recovery range of 80%–120% was set as acceptable. The inter-laboratory %CV was calculated. Results Gamma globulin background, migration pattern and concentration all affect the precision and accuracy of quantifying M-proteins by SPEP. As the background increases, imprecision increases and accuracy decreases leading to overestimation of M-protein quantitation especially evident in hypergamma samples, and more prominent with PD. Cathodal migrating M-proteins were associated with less imprecision and higher accuracy compared to central-gamma migrating M-proteins, which is attributed to the increased gamma background contribution in M-proteins migrating in the middle of the gamma fraction. There is greater imprecision and loss of accuracy at lower M-protein concentrations. Conclusions This study suggests that quantifying exceedingly low concentrations of M-proteins, although possible, may not yield adequate accuracy and precision between laboratories.

Background Electrophoretic methods to detect, characterize and quantify M-proteins play an important role in the management of patients with monoclonal gammopathies (MGs). Significant uncertainty in the quantification and limit of detection (LOD) is documented when M-proteins are <10 g/L. Using spiked sera, we aimed to assess the variability in intact M-protein quantification and LOD across 16 laboratories. Methods Sera with normal, hypo- or hyper-gammaglobulinemia were spiked with daratumumab or elotuzumab, with concentrations from 0.125 to 10 g/L (n = 62) along with a beta-migrating sample (n = 9). Laboratories blindly analyzed samples according to their serum protein electrophoresis (SPEP)/isotyping standard operating procedures. LOD and intra-laboratory percent coefficient of variation (%CV) were calculated and further specified with regard to the method (gel/capillary electrophoresis [CZE]), gating strategy (perpendicular drop [PD]/tangent skimming [TS]), isotyping (immunofixation/immunosubtraction [ISUB]) and manufacturer (Helena/Sebia). Results All M-proteins ≥1 g/L were detected by SPEP. With isotyping the LOD was moderately more sensitive than with SPEP. The intensity of polyclonal background had the biggest negative impact on LOD. Independent of the method used, the intra-laboratory imprecision of M-protein quantification was small (mean CV = 5.0%). Low M-protein concentration and high polyclonal background had the strongest negative impact on intra-laboratory precision. All laboratories were able to follow trend of M-protein concentrations down to 1 g/L. Conclusions In this study, we describe a large variation in the reported LOD for both SPEP and isotyping; overall LOD is most affected by the polyclonal immunoglobulin background. Satisfactory intra-laboratory precision was demonstrated. This indicates that the quantification of small M-proteins to monitor patients over time is appropriate, when subsequent testing is performed within the same laboratory.

Background Modern pneumatic transportation systems (PTSs) are widely used in hospitals for rapid blood sample transportation. The use of PTS may affect sample integrity. Impact on sample integrity in relation to hemolysis and platelet assays was investigated and also, we wish to outline a process-based and outcome-based validation model for this preanalytical component. Methods The effect of PTS was evaluated by drawing duplicate blood samples from healthy volunteers, one sent by PTS and the other transported manually to the core laboratory. Markers of hemolysis (potassium, lactate dehydrogenase [LD] and hemolysis index [HI]) and platelet function and activation were assessed. Historic laboratory test results of hemolysis markers measured before and after implementation of PTS were compared. Furthermore, acceleration profiles during PTS and manual transportation were obtained from a mini g logger in a sample tube. Results Hand-carried samples experienced a maximum peak acceleration of 5 g , while peaks at almost 15 g were observed for PTS. No differences were detected in results of potassium, LD, platelet function and activation between PTS and manual transport. Using past laboratory data, differences in potassium and LD significantly differed before and after PTS installation for all three lines evaluated. However, these estimated differences were not clinically significant. Conclusions In this study, we found no evidence of PTS-induced hemolysis or impact on platelet function or activation assays. Further, we did not find any clinically significant changes indicating an acceleration-dependent impact on blood sample quality. Quality assurance of PTS can be performed by surveilling outcome markers such as HI, potassium and LD.

Background This study aimed to understand the status quo of delta checks in Chinese clinical laboratories through a nationwide online survey. Methods The survey was divided into two parts. The first part was a general situation survey in which clinical laboratories had to provide information about the laboratories, including delta checks used. In the second part, clinical laboratories were asked to record the delta check alerts generated in their laboratories from June 1st, 2019 to June 30th, 2019. Results The most frequently used analytes in delta checks were potassium (K), glucose (Glu), creatinine (Cre) for clinical chemistry and hemoglobin (Hgb), platelet (PLT) count and white blood cell (WBC) count for clinical hematology. The median maximum time interval between specimens for all analytes was 5 days. The most commonly used delta check calculation modes in Chinese clinical laboratories were percentage change and absolute change. K and Hgb were the analytes most involved in clinical chemistry and clinical hematology delta check alerts. The most common causes of delta check alerts were that the patients had received treatment, which was followed by the change in the patient’s physiological state and interference from hemolysis, lipemia and icterus. The two most common outcomes of delta check alerts were ‘no problems found, standard report issued’ and ‘no problems found, report issued with comment’. Conclusions This study was the first nationwide survey of delta checks in China, the results of which help us to understand the current situation of delta checks in Chinese clinical laboratories.

Background Plasma iohexol clearance (CL iohexol ) is a reference technique for glomerular filtration rate (GFR) determination. In routine practice, CL iohexol is calculated using one of several formulas, which have never been evaluated in kidney transplant recipients. We aimed to model iohexol pharmacokinetics in this population, evaluate the predictive performance of three simplified formulas and evaluate whether a Bayesian algorithm improves CL iohexol estimation. Methods After administration of iohexol, six blood samples were drawn from 151 patients at various time points. The dataset was split into two groups, one to develop the population pharmacokinetic (POPPK) model (n = 103) and the other (n = 48) to estimate the predictive performances of the various GFR estimation methods. GFR reference values (GFR ref ) in the validation dataset were obtained by non-compartmental pharmacokinetic (PK) analysis. Predictive performances of each method were evaluated in terms of bias (ME), imprecision (root mean square error [RMSE]) and number of predictions out of the ±10% or 15% error interval around the GFR ref . Results A two-compartment model best fitted the data. The Bayesian estimator with samples drawn at 30, 120 and 270 min allowed accurate prediction of GFR ref (ME = 0.47%, RMSE = 3.42%), as did the Brøchner-Mortensen (BM) formula (ME = − 0.0425%, RMSE = 3.40%). With both methods, none of the CL estimates were outside the ±15% interval and only 2.4% were outside the ±10% for the BM formula (and none for the Bayesian estimator). In patients with GFR ≤30 mL/min/1.73 m 2 , the BM formula performed very well, while the Bayesian method could not be evaluated in depth due to too small a number of patients with adequate sampling times. Conclusions GFR can be estimated with acceptable accuracy in kidney transplant patients using the BM formula, but also using a Bayesian algorithm.

Background It has been debated whether point-of care (POC) glycated hemoglobin (HbA 1c ) measurements methods can be used for diagnosing persons with diabetes mellitus. The aim of this study was to evaluate the analytical performance of the POC Afinion HbA 1c system in the hands of the users, and to investigate which predictors that were associated with good participant performance. Methods External quality assurance (EQA) data from seven surveys in 2017–2018 with a total of 5809 Afinion participants from a POC total quality system in Norway were included in this study (response rate 90%). The control materials were freshly drawn pooled EDTA whole blood. Each participant was evaluated against the analytical performance specification of ±6% from the target value, while the Afinion system was evaluated against the pooled within-laboratory CV <2%, the between-laboratory CV <3.5%, and bias <0.3%HbA 1c . Logistic regression analyses were used to investigate which factors were associated with good participant performance. Results The participant pass rates for each survey varied from 98.2% to 99.7%. The pooled within-laboratory CV varied from 1.3% to 1.5%, the between-laboratory CV varied from 1.5% to 2.1%, and bias varied between −0.17 and −0.01 %HbA 1c in all surveys. Reagent lot was the only independent factor to predict good participant performance. Conclusions Afinion HbA 1c fulfilled the analytical performance specifications and is robust in the hands of the users. It can therefore be used both in diagnosing and monitoring persons with diabetes mellitus, given that the instrument is monitored by an EQA system.

Background Diagnosis of upper urinary tract infections (UTI) is challenging. We evaluated the analytical and diagnostic performance characteristics of renal tubular epithelial cells (RTECs) and transitional epithelial cells (TECs) on the Sysmex UF-5000 urine sediment analyzer. Methods Urinary samples from 506 patients presenting with symptoms of a UTI were collected. Only samples for which a urinary culture was available were included. Analytical (imprecision, accuracy, stability and correlation with manual microscopy) and diagnostic performance (sensitivity and specificity) were evaluated. Results The Sysmex UF-5000 demonstrated a good analytical performance. Depending on the storage time, storage conditions (2–8 °C or 20–25 °C) and urinary pH, RTECs and TECs were stable in urine for at least 4 h. Using Passing-Bablok and Bland-Altman analysis, an acceptable agreement was observed between the manual and automated methods. Compared to TECs, RTECs demonstrated an acceptable diagnostic performance for the diagnosis of upper UTI. Conclusions While TECs do not seem to serve as a helpful marker, increased urinary levels of RTECs add value in the diagnosis of upper UTI and may be helpful in the discrimination between upper and lower UTIs.

Background Accurate pediatric reference intervals (RIs) for laboratory tests determined in a healthy pediatric population are essential for correct laboratory test interpretation and clinical decision-making. In pediatrics, RIs require partitioning by age and/or sex; however, the need for partitioning based on ethnicity is unclear. Here, we assessed the influence of ethnicity on biomarker concentrations in the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort of healthy children and adolescents and compared the results with the National Health and Nutrition Examination Survey (NHANES). Methods A total of 52 biomarkers were measured in a multiethnic population of 846–1179 healthy children (aged 5 to <19 years) upon informed consent. Biomarker concentrations were retrospectively compared between four major ethnic groups (i.e. Black, Caucasian, East Asian, and South Asian, determined by parental ethnicity). Retrospective results were verified prospectively using an additional 500 healthy pediatric samples with equal sample size across ethnicities. Ethnic-specific differences were assessed based on statistical significance and biological and analytical variations. Appropriate age-, sex-, and ethnic-specific RIs were calculated. Results Ethnic-specific differences were not observed for 34 biomarkers examined in the retrospective analysis, while 18 demonstrated statistically significant ethnic differences. Among these, seven analytes demonstrated ethnic-specific differences in the prospective analysis: vitamin D, amylase, ferritin, follicle-stimulating hormone (FSH), immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM). Analysis of select NHANES data confirmed CALIPER findings. Conclusions This is the first comprehensive Canadian pediatric study examining ethnic-specific differences in common biomarkers. While the majority of biomarkers did not require ethnic partitioning, ethnic-specific RIs were established for seven biomarkers showing marked differences. Further studies in other populations are needed to confirm our findings.

Background Capillary B-type natriuretic peptide (BNP) testing is attractive in outpatient and emergency settings. The aim of this study was to perform an evaluation of the clinical performances of capillary BNP testing as compared with venous whole blood and plasma point-of-care (POC) BNP as well as plasma N-terminal (NT) proBNP central laboratory testing. Methods BNP was measured with a novel single epitope POC assay (Minicare ® BV, Eindhoven, The Netherlands) and NT-proBNP with a central laboratory assay (Roche Diagnostics ® , Vienna, Austria). Results BNP and NT-proBNP were measured in 269 patients of a Department of Cardiology (mean age 67.9 ± 13 years, 26.4% females). Capillary BNP very closely correlated with whole blood venous BNP (r = 0.99, p < 0.001). There was also a close correlation of plasma BNP and NT-proBNP concentrations (r = 0.79, p < 0.001). The diagnostic performances of capillary BNP, whole blood venous BNP, plasma BNP and plasma NT-proBNP for acute heart failure (areas under receiver operating characteristic curves [AUC ROC]: 0.73–0.77) or systolic left ventricular dysfunction in the whole study population (AUC ROC: 0.72–0.76) did not differ significantly. All were significant independent predictors of cardiovascular death during follow-up of the whole study population. Conclusions Our study for the first time demonstrated a very close correlation of capillary and venous whole blood or plasma BNP concentrations using the same BNP assay in a large patient cohort. The diagnostic performances of different BNP specimens did not differ significantly, and no significant differences between BNP and NT-proBNP were found either.

Background Both the thrombo-inflammatory prognostic score (TIPS) and the quick sequential (sepsis-related) organ failure assessment (qSOFA) are quick prognostic scores for sepsis during the early phase, while either of two scores has limited prognostic value for sepsis patients. This study aimed to evaluate whether TIPS adds more information of sepsis risk stratification for qSOFA. Methods This was a retrospective cohort study of patients with sepsis in the emergency department (ED). We performed a receiver-operating characteristic curve, integrated discrimination improvement (IDI), net reclassification improvement (NRI) and decision-curve analysis (DCA) analyses to investigate whether TIPS can improve qSOFA for risk prediction in patients with sepsis. The primary endpoint was mortality and the secondary endpoints were mechanical ventilation and admission to the intensive care unit (ICU) during the 28-day follow-up. Results We identified 821 patients with sepsis. We randomly assigned the patients’ data to a derivation group (n = 498; n = 112 died during the 28-days follow-up) or to a validation group (n = 323; n = 61). The addition of TIPS to qSOFA (T-qSOFA) improved the area under the curve (AUC) from 0.724 to 0.824 (p < 0.001) for predicting 28-day mortality. The discrimination improvement was confirmed by an IDI of 0.092 (p < 0.001). Addition of TIPS to the qSOFA resulted in a NRI of 0.247 (p < 0.001). The DCA showed that the net benefit of T-qSOFA was higher than that of TIPS or qSOFA for any threshold probabilities. Conclusions The prognostic value of qSOFA for patients with sepsis was enhanced by adding the TIPS score on admission for risk prediction in patients with sepsis during early phases in the ED.