Band 55, Heft 2

Background: Point-of-care (POC) devices could be used to measure hemoglobin A 1c (HbA 1c ) in the doctors’ office, allowing immediate feedback of results to patients. Reports have raised concerns about the analytical performance of some of these devices. We carried out a systematic review and meta-analysis using a novel approach to compare the accuracy and precision of POC HbA 1c devices. Methods: Medline, Embase and Web of Science databases were searched in June 2015 for published reports comparing POC HbA 1c devices with laboratory methods. Two reviewers screened articles and extracted data on bias, precision and diagnostic accuracy. Mean bias and variability between the POC and laboratory test were combined in a meta-analysis. Study quality was assessed using the QUADAS2 tool. Results: Two researchers independently reviewed 1739 records for eligibility. Sixty-one studies were included in the meta-analysis of mean bias. Devices evaluated were A1cgear, A1cNow, Afinion, B-analyst, Clover, Cobas b101, DCA 2000/Vantage, HemoCue, Innovastar, Nycocard, Quo-Lab, Quo-Test and SDA1cCare. Nine devices had a negative mean bias which was significant for three devices. There was substantial variability in bias within devices. There was no difference in bias between clinical or laboratory operators in two devices. Conclusions: This is the first meta-analysis to directly compare performance of POC HbA 1c devices. Use of a device with a mean negative bias compared to a laboratory method may lead to higher levels of glycemia and a lower risk of hypoglycaemia. The implications of this on clinical decision-making and patient outcomes now need to be tested in a randomized trial.

Background: The pathogenesis of different types of myocardial infarction (MI) differs widely, so that accurate and timely differential diagnosis is essential for tailoring treatments according to the underlying causal mechanisms. As the measurement of cardiac troponins is a mainstay for diagnosis and management of MI, we performed a systematic literature analysis of published works which concomitantly measured cardiac troponins in type 1 and 2 MI. Methods: The electronic search was conducted in Medline, Scopus and Web of Science using the keywords “myocardial infarction” AND “type(-)2” OR “type II” AND “troponin” in “Title/Abstract/Keywords”, with no language restriction and date limited from 2007 to the present. Results: Overall, 103 documents were identified, but 95 were excluded as precise comparison of troponin values in patients with type 1 and 2 MI was unavailable. Therefore, eight studies were finally selected for our analysis. Two studies used high-sensitivity (HS) immunoassays for measuring cardiac troponin T (HS-TnT), one used a HS immunoassay for measuring cardiac troponin I (HS-TnI), whereas the remaining used conventional methods for measuring TnI. In all studies, regardless of type and assay sensitivity, troponin values were higher in type 1 than in type 2 MI. The weighted percentage difference between type 1 and 2 MI was 32% for TnT and 91% for TnI, respectively. Post-discharge mortality obtained from pooling individual data was instead three times higher in type 2 than in type 1 MI. Conclusions: The results of our analysis suggest that the value of cardiac troponins is consistently higher in type 1 than in type 2 MI.

This paper, prepared by the EFLM Task and Finish Group on Allocation of laboratory tests to different models for performance specifications (TFG-DM), is dealing with criteria for allocating measurands to the different models for analytical performance specifications (APS) recognized in the 1st EFLM Strategic Conference Consensus Statement. Model 1, based on the effect of APS on clinical outcome, is the model of choice for measurands that have a central role in the decision-making of a specific disease or clinical situation and where cut-off/decision limits are established for either diagnosing, screening or monitoring. Total cholesterol, glucose, HbA 1c , serum albumin and cardiac troponins represent practical examples. Model 2 is based on components of biological variation and should be applied to measurands that do not have a central role in a specific disease or clinical situation, but where the concentration of the measurand is in a steady state. This is best achieved for measurands under strict homeostatic control in order to preserve their concentrations in the body fluid of interest, but it can also be applied to other measurands that are in a steady state in biological fluids. In this case, it is expected that the “noise” produced by the measurement procedure will not significantly alter the signal provided by the concentration of the measurand. This model especially applies to electrolytes and minerals in blood plasma (sodium, potassium, chloride, bicarbonate, calcium, magnesium, inorganic phosphate) and to creatinine, cystatin C, uric acid and total protein in plasma. Model 3, based on state-of-the-art of the measurement, should be used for all the measurands that cannot be included in models 1 or 2.

Background: Human papillomavirus (HPV) DNA detection and genotyping is now being used for cervical screening by a growing number of laboratories in Shanghai, but they may have various levels of proficiency. The objective of this study was to evaluate the performance of clinical laboratories for HPV DNA detection and genotyping by an external quality assessment (EQA) program. Methods: The EQA panels were clinically validated by the Cobas 4800 HPV test, and then distributed to the participating laboratories in May 2015 (round 1) and September 2015 (round 2). Each panel consisted of one negative sample and nine positive cell or clinical samples of HPV16 and HPV18 types at different concentrations. In total, 40 laboratories submitted 18 qualitative and 22 genotyping data sets in round 1 and 44 laboratories submitted 18 qualitative and 26 genotyping data sets in round 2. In both rounds, all laboratories used commercial assays. Results: The negative samples were detected correctly in both rounds by all participating laboratories. There were no false-positive results in the qualitative data sets and only two false-positive results in the genotyping data sets in each of round 1 and round 2. The false-negative rates were 8.0% for round 1 and 2.7% for round 2. For the qualitative data sets, almost all of the laboratories (100% for round 1 and 97.8% for round 2) obtained a score of acceptable or better. For the genotyping results, acceptable or better scores were obtained in 81.8% (round 1) and 100% (round 2). Conclusions: Our results indicate that the majority of laboratories in Shanghai have reliable diagnostic ability for HPV detection and genotyping. Moreover, this study emphasizes the importance of EQA for monitoring the performance of clinical laboratories.

Background: Optimum patient care in relation to laboratory medicine is achieved when results of laboratory tests are equivalent, irrespective of the analytical platform used or the country where the laboratory is located. Standardization and harmonization minimize differences and the success of efforts to achieve this can be monitored with international category 1 external quality assessment (EQA) programs. Methods: An EQA project with commutable samples, targeted with reference measurement procedures (RMPs) was organized by EQA institutes in Italy, the Netherlands, Portugal, UK, and Spain. Results of 17 general chemistry analytes were evaluated across countries and across manufacturers according to performance specifications derived from biological variation (BV). Results: For K, uric acid, glucose, cholesterol and high-density density (HDL) cholesterol, the minimum performance specification was met in all countries and by all manufacturers. For Na, Cl, and Ca, the minimum performance specifications were met by none of the countries and manufacturers. For enzymes, the situation was complicated, as standardization of results of enzymes toward RMPs was still not achieved in 20% of the laboratories and questionable in the remaining 80%. Conclusions: The overall performance of the measurement of 17 general chemistry analytes in European medical laboratories met the minimum performance specifications. In this general picture, there were no significant differences per country and no significant differences per manufacturer. There were major differences between the analytes. There were six analytes for which the minimum quality specifications were not met and manufacturers should improve their performance for these analytes. Standardization of results of enzymes requires ongoing efforts.

Background: Results from external quality assessment schemes (EQASs) can provide information about accuracy and comparability of different measurement methods, provided that the material used in these schemes behave identical to patient samples among the different methods, a characteristic also known as commutability. The aim of this study was to assess the commutability of different matrices for the material used in an EQAS for tobramycin. Methods: Proficiency testing material (PTM) and patient samples containing tobramycin were prepared, collected, pooled, and distributed to participating laboratories for analysis. Low, medium, and high tobramycin concentrations in liquid human, liquid bovine and lyophilized bovine serum were tested in this study. The patient serum results of every laboratory were plotted against each of the other laboratories, and the distances of the PTM results to the patient serum regression line were calculated. For comparison, these distances were divided by the average within-laboratory standard deviation (SD wl ) of the results reported in the official EQAS for tobramycin, resulting in a relative residual. The commutability decision limit was set at 3 SD wl . Results: With 10 laboratories participating in this study, 45 laboratory couples were formed. For human serum, only one relative residual for high concentrations of tobramycin was found outside the commutability decision limit. For liquid and lyophilized bovine sera, the number of relative residuals outside the decision limit was between 15 and 18 for low, medium, and high tobramycin concentrations. Conclusions: The PTM used for tobramycin is preferably prepared with human serum.

Background: To date, no practical tools are available to obtain optimal settings for moving average (MA) as a continuous analytical quality control instrument. Also, there is no knowledge of the true bias detection properties of applied MA. We describe the use of bias detection curves for MA optimization and MA validation charts for validation of MA. Methods: MA optimization was performed on a data set of previously obtained consecutive assay results. Bias introduction and MA bias detection were simulated for multiple MA procedures (combination of truncation limits, calculation algorithms and control limits) and performed for various biases. Bias detection curves were generated by plotting the median number of test results needed for bias detection against the simulated introduced bias. In MA validation charts the minimum, median, and maximum numbers of assay results required for MA bias detection are shown for various bias. Their use was demonstrated for sodium, potassium, and albumin. Results: Bias detection curves allowed optimization of MA settings by graphical comparison of bias detection properties of multiple MA. The optimal MA was selected based on the bias detection characteristics obtained. MA validation charts were generated for selected optimal MA and provided insight into the range of results required for MA bias detection. Conclusions: Bias detection curves and MA validation charts are useful tools for optimization and validation of MA procedures.

Background: The innovative pneumatic tube system (iPTS) transports one sample at a time without the use of cartridges and allows rapid sending of samples directly into the bulk loader of a laboratory automation system (LAS). We investigated effects of the iPTS on samples and turn-around time (TAT). Methods: During transport, a mini data logger recorded the accelerations in three dimensions and reported them in arbitrary area under the curve (AUC) units. In addition representative quantities of clinical chemistry, hematology and coagulation were measured and compared in 20 blood sample pairs transported by iPTS and courier. Results: Samples transported by iPTS were brought to the laboratory (300 m) within 30 s without adverse effects on the samples. The information retrieved from the data logger showed a median AUC of 7 and 310 arbitrary units for courier and iPTS transport, respectively. This is considerably below the reported limit for noticeable hemolysis of 500 arbitrary units. Conclusions: iPTS reduces TAT by reducing the hands-on time and a fast transport. No differences in the measurement results were found for any of the investigated 36 analytes between courier and iPTS transport. Based on these findings the iPTS was cleared for clinical use in our hospital.

Background: Saving resources is a paramount issue for the modern laboratory, and new trainable as well as smart technologies can be used to allow the automated instrumentation to manage samples more efficiently in order to achieve streamlined processes. In this regard the serum free light chain (sFLC) testing represents an interesting challenge, as it usually causes using a number of assays before achieving an acceptable result within the analytical range. Methods: An artificial neural network based on the multi-layer perceptron (MLP-ANN) was used to infer the starting dilution status of sFLC samples based on the information available through the laboratory information system (LIS). After the learning phase, the MLP-ANN simulation was applied to the nephelometric testing routinely performed in our laboratory on a BN ProSpec ® System analyzer (Siemens Helathcare) using the N Latex FLC kit. Results: The MLP-ANN reduced the serum kappa free light chain (κ-FLC) and serum lambda free light chain (λ-FLC) wasted tests by 69.4% and 70.8% with respect to the naïve stepwise dilution scheme used by the automated analyzer, and by 64.9% and 66.9% compared to a “rational” dilution scheme based on a 4-step dilution. Conclusions: Although it was restricted to follow-up samples, the MLP-ANN showed good predictive performance, which alongside the possibility to implement it in any automated system, made it a suitable solution for achieving streamlined laboratory processes and saving resources.

Background: Urine represents an ideal source of clinically relevant biomarkers as it contains a large number of proteins and low molecular weight peptides. The comprehensive characterization of the normal urinary proteome and peptidome can serve as a reference for future biomarker discovery. Proteomic and peptidomic analysis of urine can also provide insight into normal physiology and disease pathology, especially for urogenital diseases. Methods: We developed an integrated proteomic and peptidomic analytical protocol in normal urine. We employed ultrafiltration to separate protein and peptide fractions, which were analyzed separately using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) on the Q-Exactive mass spectrometer. Results: By analyzing six urines from healthy individuals with advanced age, we identified 1754 proteins by proteomic analysis and 4543 endogenous peptides, arising from 566 proteins by peptidomic analysis. Overall, we identified 2091 non-redundant proteins by this integrated approach. In silico protease activity analysis indicated that metalloproteases are predominantly involved in the generation of the endogenous peptide signature. In addition, a number of proteins that were detected in normal urine have previously been implicated in various urological malignancies, including bladder cancer and renal cell carcinoma (RCC). Conclusions: We utilized a highly sensitive proteomics approach that enabled us to identify one of the largest sets of protein identifications documented in normal human urine. The raw proteomics and peptidomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD003595.

Background: Inhibition assays are an useful tool to identify the allergen of primary sensitization of cross-reactive allergens. Classical ELISA-based inhibition assays are limited by both the availability of commercial standardized allergen extracts and the experience and knowledge needed for making home-made extracts. Moreover the direct comparison of the inhibition ELISAs outcomes between different laboratories is difficult because of different sources of used allergen extracts and a number of methodological variations. Therefore, we propose a novel ImmunoCap (Phadia, Thermofisher Scientific) based immunoinhibition method with the use of commercially available Caps as the allergen source. Methods: The novel ImmunoCap based immunoinhibition method was developed and tested with sera from patients with a well-known cross-reactive sensitization for fig ( Ficus carica ) and ficus (Ficus benjamina ). Results were compared with a classically applied inhibition method, i.e. addition of homemade allergen extract to patient serum. Results: The amount of allergens (fig and ficus extracts) needed to reach a similar degree of inhibition was comparable for both inhibition methods. Conclusions: The ImmunoCap based inhibition assay, in addition to classical inhibition methods, is a valuable tool as the ImmunoCap analyzer and commercial allergens (Caps) are more widely available which makes the outcomes of inhibition tests comparable between different laboratories. Furthermore, in the ImmunoCap inhibition method the same protein source is used for both the inhibition of sIgE and sIgE measurement, which might be even more relevant when multiple cross-reactive allergens are tested.

Background: Abnormal α-synuclein aggregation and deposition is the pathological hallmark of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB), but is also found in Alzheimer disease (AD). Therefore, there is a gaining interest in α-synuclein in cerebrospinal fluid (CSF) as potential biomarker for these neurodegenerative diseases. To broaden the available choices of α-synuclein measurement in CSF, we developed and validated a new assay for detecting total α-synuclein. Methods: This novel ELISA uses commercially available antibodies and is based on electrochemiluminescence technology. The assay protocol is straightforward, with short and simple incubation steps, and requires only small amounts of CSF. We validated this assay for precision, parallelism, dilution linearity, specificity, and spike recovery. We further compared it to the newly validated α-synuclein assay from BioLegend by analyzing a set of 50 CSF samples with both assays. Results: The new assay quantifies α-synuclein in CSF with a lower limit of detection of 36.3 pg/mL and shows no cross-reactivity with human β- and γ-synuclein. Results of dilution linearity, parallelism, spike recovery, and precision classify this assay as well suited for α-synuclein detection in human CSF samples. Conclusions: We present a novel assay based on freely available components to quantify total α-synuclein in CSF as an additional method for α-synuclein as a biomarker in neurodegenerative diseases. The assay convinces with its simple and convenient protocol paired with high sensitivity.

Background: Circulating trimethylamine- N -oxide (TMAO) has been implicated in the development of cardiovascular and chronic kidney diseases (CKD). However, while higher TMAO levels have been associated with increased risks of cardiovascular or renal events in first prospective studies, it remained unclear how much plasma TMAO concentrations vary over time. Methods: We measured fasting plasma levels of TMAO and two of its precursors, betaine and choline by LC-MS, in two samples of 100 participants of the European Investigation into Cancer and Nutrition (EPIC)-Heidelberg study (age range: 47–80 years, 50% female) that were collected 1 year apart, and assessed their intra-individual variation by Spearman’s correlation coefficients (ρ). Results: Correlations of metabolite concentrations over 1 year were at ρ=0.29 (p=0.003) for TMAO, ρ=0.81 (p<0.001) for betaine, and ρ=0.61 (p<0.001) for choline. Plasma levels of TMAO were not significantly associated with food intake, lifestyle factors, or routine biochemistry parameters such as C-reactive protein (CRP), low-density lipoprotein (LDL)-cholesterol, or creatinine. Conclusions: In contrast to fasting plasma concentrations of betaine and choline, concentrations of TMAO were more strongly affected by intra-individual variation over 1 year in adults from the general population. The modest correlation of TMAO levels over time should be considered when interpreting associations between TMAO levels and disease endpoints.

Background: The aim of the present study was to investigate the predictive performance of serial tissue polypeptide antigen (TPA) testing after curative intent resection for detection of recurrence of colorectal malignancy. Methods: Serum samples were obtained in 572 patients from three different hospitals during follow-up after surgery. Test characteristics of serial TPA testing were assessed using a cut-off value of 75 U/L. The relation with American Joint Committee on Cancer stage and the potential additive value of tissue polypeptide antigen testing upon standard carcinoembryonic antigen (CEA) testing were investigated. Results: The area under the receiver operating characteristic curve of TPA for recurrent disease was 0.70, indicating marginal usefulness as a predictive test. Forty percent of cases that were detected by CEA testing would have been missed by TPA testing alone, whilst most cases missed by CEA were also not detected by TPA testing. In the subpopulation of patients with stage III disease predictive performance was good (area under the curve 0.92 within 30 days of diagnosing recurrent disease). In this group of patients, 86% of cases that were detected by CEA were also detected by TPA. Conclusions: Overall, TPA is a relatively poor predictor for recurrent disease during follow-up. When looking at the specific subpopulation of patients with stage III disease predictive performance of TPA was good. However, TPA testing was not found to be superior to CEA testing in this specific subpopulation.

Background: This study aimed to assess the association of mid-regional (MR) pro-adrenomedullin (MR-proADM) and MR-pro-A-type natriuretic peptide (MR-proANP) in comparison to N-terminal pro-natriuretic peptide (NT-proBNP) with outcome in patients with aortic stenosis (AS) treated with transcatheter aortic valve implantation (TAVI). Methods: One hundred consecutive TAVI patients were included in this prospective study. Association of preinterventional levels of MR-proADM, MR-proANP, NT-proBNP, C-reactive protein (CrP), and high-sensitive cardiac Troponin T (hsTN) with 30-day and 1-year outcome was analyzed. Results: There was no association with 30-day outcome, but all markers were associated with 1-year cardiovascular events and all-cause mortality. The combined biomarker analysis further improved risk prediction. Conclusions: In TAVI patients MR-proADM, MR-proANP, and NT-proBNP are promising predictors of adverse events within 1 year. Integration of these biomarkers into decision pathways may help to identify patients at higher risk.

Background: Although several studies have explored the genetic polymorphisms of apolipoprotein E ( APOE ) and their impact on premature coronary artery disease (PCAD), there is still some controversy regarding the significance of their association. Our aim is to estimate the association between APOE polymorphisms and PCAD via meta-analysis. Methods: All relevant case-control studies and cohort studies published in Chinese or English prior to March 2016 were searched for in electronic databases. Detailed information concerning each piece of literature was independently extracted by two researchers. We used STATA11.0 to process all data and to determine the pooled odds ratio (OR). Altogether, four genetic models were applied to calculate OR and 95% confidence interval (CI): (1) ε2 allele vs. ε3 allele; (2) ε2 carriers vs. ε3/3 ; (3) ε4 allele vs. ε3 allele; (4) ε4 carriers vs. ε3/3 . Results: Eighteen studies concerning APOE polymorphisms and their impact on PCAD were included in the final analysis. The pooled analysis displayed that the ε2 allele and ε2 carriers increased the risk of PCAD significantly among Asians (OR 1.54; 95% CI, 1.09–2.17; OR 1.65; 1.10–2.47), while they showed protective effects on PCAD in Caucasians (OR 0.77; 95% CI, 0.62–0.95; OR 0.69; 0.54–0.89). Subjects with the ε4 allele and ε4 carriers showed significant associations with PCAD (OR 1.62; 95% CI, 1.27–2.06; OR 1.65; 1.27–2.15). Conclusions: Our investigation supported the fact that the ε2 allele in APOE may appear as a risk factor for PCAD in Asians while a protective factor in Caucasians and that the ε4 allele acted as a genetic risk factor for PCAD.

Background: In order to help clinical decision making, we investigated the diagnostic and prognostic ability of urinary orosomucoid (u-ORM) as a new sepsis biomarker, and compared its performance to classical inflammatory parameters. Methods: We monitored u-ORM in septic (n=43) and SIRS (n=13) patients in a 5-day follow-up study vs. control patients (n=30). U-ORM was measured by a newly developed turbidimetric assay. U-ORM values were referred to urinary creatinine and expressed as u-ORM/u-CREAT (mg/mmol). Results: Significantly higher (p<0.001) u-ORM/u-CREAT levels were found in sepsis than in SIRS. Both intensive care unit (ICU) groups showed strongly elevated values compared to controls (p<0.001). The medians of admission u-ORM/u-CREAT levels were 19.2 in sepsis, 2.1 in SIRS and 0.2 mg/mmol in controls. The area under the receiver operating characteristic curve for distinguishing SIRS from sepsis was found to be 0.954 for u-ORM/u-CREAT, superior to serum ORM and hsCRP. U-ORM levels did not change during the 5-day follow-up and were independent of the severity of sepsis however, we found extremely elevated u-ORM/u-CREAT values in dialyzed septic patients (52.2 mg/mmol as median). Conclusions: The early and relevant increase of u-ORM in sepsis suggests that it might be a promising novel marker of sepsis and could be a valuable part of routine laboratory and clinical practice.