bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization procedure for ion-selective electrode assays of magnesium activity in aqueous solutions of physiological composition
Authors: Eugster R , Rusterholz B , Schmid A , Spichiger U E , Simon W
Published: January 2020

A magnesium ion-selective liquid membrane electrode based on a synthetic neutral carrier is presented. The selectivity for Mg2+ over Na+, K+, and H+ is sufficient for assays in the physiological range, but a chemometric correction of approximately 10% is still necessary for the Ca2+ interference. We optimized the membrane composition especially with respect to selectivity and accuracy by performing a new characterization procedure in which we simulated the variety of blood serum samples with 10 aqueous solutions. After a three-point calibration, these solutions were measured alternately with the middlerange calibrator for 3 min. The magnesium activity was evaluated after correcting for the calcium interference according to the Nikolsky equation. The selectivity coefficient, KpotMgCa, was itself fitted to give the minimum deviations from the assigned magnesium activities. Electrodes with an optimized membrane composition show an average deviation from theoretical activity values of about 1.6% with logKpotMgCa = -0.8.
Evaluation of seven Cholestech L.D.X analyzers for total cholesterol determinations
Authors: Rogers E J , Misner L , Ockene I S , Nicolosi R J
Published: January 2020

We assessed the performance of seven Cholestech L.D.X lipid analyzers under tightly controlled laboratory conditions for accuracy and precision in accordance with analytical guidelines of the National Cholesterol Education Program (NCEP). Venous heparinized whole blood (VB) and plasma (VP), venous serum (VS), and capillary fingerstick whole blood (FB) were collected from 18 individuals. Total cholesterol (TC) concentration was measured in VB, VP, and VS on all seven instruments. Three instruments were used for TC measurements of FB. Reference cholesterol values for each individual were generated in the same laboratory with a standardized method. The within-run coefficients of variation (CVs) for all instruments with a Level I pool (1560 mg/L, n = 10) ranged from 1.3% to 1.8% (mean = 1.59%). The between-run CVs with the same pool ranged from 2.2% to 3.4% (mean = 2.84%, n = 10). Correlation coefficients derived from comparison of total cholesterol values generated by the instruments for each specimen type vs the reference cholesterol values were all > 0.97. The average bias for all instruments for each sample type was 1.9% (FB), 4.3% (VB), 6.6% (VP), and 7.0% (VS). Predicted cholesterol concentration for each sample type from regression curves for total cholesterol at the suggested NCEP clinical decision cutoff values of 2000 and 2400 mg/L, respectively, were 2049 and 2431 mg/L for FB, 2081 and 2469 mg/L for VB, 2122 and 2522 mg/L for VP, and 2121 and 2521 mg/L for VS.
3-Hydroxydicarboxylic and 3-ketodicarboxylic aciduria in three patients: evidence for a new defect in fatty acid oxidation at the level of 3-ketoacyl-CoA thiolase
Authors: Bennett M J , Sherwood W G
Published: January 2020

Three patients presented with evidence of a fatty acid oxidation disorder. Analysis of urinary organic acids by gas chromatography/mass spectrometry demonstrated the presence of medium-chain (C6-C12) dicarboxylic, 3-hydroxydicarboxylic, and 3-ketodicarboxylic acids in all three urines. 3-Ketodicarboxylic aciduria is reported for the first time here, as are the mass spectra for 3-ketosuberic, 3-ketosebacic, and 3-ketododecanedioic acids and the oximated spectrum for 3-ketoadipic acid. The presence of 3-ketodicarboxylic acids suggests a defect at the level of a long-chain 3-ketoacyl-CoA thiolase, an enzyme for which a deficiency state has not previously been described. Our patients may represent the first cases of a long-chain thiolase defect.
Glutamine stability in biological tissues evaluated by fluorometric analysis
Authors: Grossie V B , Yick J , Alpeter M , Welbourne T C , Ota D M
Published: January 2020

Although glutamine has been considered unstable during storage and therefore difficult to quantitate, recent results suggest this amino acid is stable at low pH ranges. We evaluated the stability of glutamine in plasma and tissue extracts, using fluorometric analysis. The measured concentration of glutamine detected varied linearly up to 0.8 mmol/L for the aqueous solution (r2 = 98.7, P = 0.0001) with a mean (+/- SD) coefficient of variation of 2.41% +/- 0.79%. When glutamine was dissolved in 50 g/L trichloroacetic acid (TCA), the values were essentially unaltered. Glutamine in an aqueous solution and stored at -70 degrees C was stable for at least 16 days; glutamine in TCA was stable for 6-8 days, then decreased to a concentration significantly lower than that of the aqueous solution. The expected and observed concentrations in plasma were equal (r2 = 0.99975) for increasing amounts of added glutamine. Glutamine concentrations in plasma were stable for > 1 year when stored at -70 degrees C. The glutamine of a transplantable rat sarcoma and a normal rat liver could be extracted with 50 g/L TCA with high efficiency (88.6% +/- 1.9% and 90.2% +/- 0.04%, respectively); the extracted glutamine is stable in TCA for at least 7 days without neutralization when stored at -70 degrees C. Fluorometric analysis of glutamine required only a small quantity of plasma (25 microL) or tissue (200 mg) and is a convenient method for quantifying this important amino acid.
Cross-reactivities of cyclosporin G (NVa2 cyclosporin) and metabolites in cyclosporin A immunoassays
Authors: Yatscoff R W , Langman L J , LeGatt D F
Published: January 2020

Immunoassays of cyclosporin A (CsA) have been routinely used to measure CsG. We investigated the cross-reactivities of CsG and its metabolites, as well as the proportion CsG constitutes in relation to total drug measured, for six CsG metabolites (GM1, GM9, GM4N, GM1c, GM1c9, GM19) in the following CsA assays: Sandimmune selective RIA (SS), Sandimmune nonselective RIA (NS), Cyclotrac SP-RIA (CT), fluorescence polarization immunoassay (FPIA), and enzyme immunoassay (EMIT). The cross-reactivity of CsG in these assays was as follows: SS, FPIA, CT, approximately 100%; NS, approximately 40%; EMIT, < 2%. The cross-reactivities of CsG metabolites were investigated in all assays except EMIT and varied among metabolites and assays. The most significant variance was found with the NS assay, where most of the metabolites exhibited cross-reactivities of > 40%. In contrast, in the SS, FPIA, and CT assays, cross-reactivities of < 5% were observed for most of the metabolites. The ranking of cross-reactivities of CsG metabolites in the assays is SS = CT < FPIA < NS. The degree of cross-reactivity did not change significantly when the SS, CT, and FPIA assays were calibrated with CsG instead of CsA--whether parent CsG was present or not. The data suggest that the SS, CT, and FPIA methods would be suitable for the routine monitoring of CsG.
Partial least-squares regression for routine analysis of urinary calculus composition with Fourier transform infrared analysis
Authors: Volmer M , Bolck A , Wolthers B G , de Ruiter A J , Doornbos D A , van der Slik W
Published: January 2020

Quantitative assessment of urinary calculus (renal stone) constituents by infrared analysis (IR) is hampered by the need of expert knowledge for spectrum interpretation. Our laboratory performed a computerized search of several libraries, containing 235 reference spectra from various mixtures with different proportions. Library search was followed by visual interpretation of band intensities for more precise semiquantitative determination of the composition. We tested partial least-squares (PLS) regression for the most frequently occurring compositions of urinary calculi. Using a constrained mixture design, we prepared various samples containing whewellite, weddellite, and carbonate apatite and used these as a calibration set for PLS regression. The value of PLS analysis was investigated by the assay of known artificial mixtures and selected patients' samples for which the semiquantitative compositions were determined by computerized library search followed by visual interpretation. Compared with that method, PLS analysis was superior with respect to accuracy and necessity of expert knowledge. Apart from some practical limitations in data-handling facilities, we believe that PLS regression offers a promising tool for routine quantification, not only for whewellite, weddellite, and carbonate apatite, but also for other compositions of the urinary calculus.
Plasma immunoreactive endothelin in the acute and subacute phases of myocardial infarction in patients undergoing fibrinolysis
Authors: Lechleitner P , Genser N , Mair J , Maier J , Artner-Dworzak E , Dienstl F , Puschendorf B
Published: January 2020

Endothelin is a potent vasoconstrictor of coronary arteries. We measured plasma concentrations of immunoreactive endothelin (irET) in 46 patients with confirmed acute myocardial infarction (AMI). When compared with irET concentrations in healthy individuals who served as controls, irET concentrations in patients were already significantly elevated at the time of admission (P = 0.002) and remained significantly elevated for at least 2 days after AMI (P < 0.01). IrET concentrations peaked 1 h (mean) after admission (8.5 +/- 3.9 ng/L, P = 0.02 compared with values at time of admission). Reperfusion of the infarct-related artery markedly influenced irET release. Before the start of thrombolytic therapy, irET concentration in patients with early reperfusion did not differ significantly from that of those without early reperfusion. However, irET time courses were significantly (P = 0.03 by analysis of variance) different in patients who did and did not have early reperfusion. In the latter, peak irET concentrations correlated closely with the angiographic left ventricular ejection fraction (r = -0.71, P = 0.03), maximum creatine kinase MB mass concentrations (r = 0.69, P = 0.01), and creatine kinase activities (r = 0.59, P = 0.03). Reflow and reversion of myocardial ischemia are associated with a reduced irET release in patients with AMI.
Candidate reference methods for determining target values for cholesterol, creatinine, uric acid, and glucose in external quality assessment and internal accuracy control. I. Method setup
Authors: Stöckl D , Reinauer H
Published: January 2020

In Germany, the target values for External Quality Assessment (EQA) and internal accuracy control are determined by Reference Methods for several analytes, including cholesterol, creatinine, uric acid, and glucose. We present candidate Reference Methods for these compounds, based on isotope dilution-gas chromatography--mass spectrometry methods that have been developed at INSTAND, one of the two official Germany EQA reference institutions. Each Reference Method target value is calculated from six independent measurements performed on three different days. The mean method CVs ranged from 0.66% for glucose to 0.96% for creatinine. The inaccuracy (bias) of the methods is < 0.7%, as compared with the Standard Reference Material 909 of the National Institute of Standards and Technology. The maximum total error of a Reference Method value, including the 95% confidence interval and systematic errors, is < 2.3%. The presented candidate Reference Methods have been successfully used to set target values in the German EQA scheme and the internal accuracy control of routine laboratories.
General approach to correction for bias in analytical performance in longitudinal studies illustrated by estimating the effect of age on gamma-glutamyltransferase activity
Authors: van der Meulen E A , van Sittert N J , de Koningh A G , Lugtenburg D , van Strik R
Published: January 2020

For studying trends in blood biochemistry analytes of an individual or a group of individuals, the outcome may be influenced by analytical changes that may have occurred during the study. An observed trend may well represent a drift in analytical performance instead of a truly biological finding. We developed a model that allows for retrospective correction of analytical changes with time. This model is based on the concept of adjustment of an individual's longitudinal blood biochemistry data by comparing the long-term results of the laboratory with those of other laboratories in an external quality-control survey program. Factors responsible for the analytical bias of our laboratory were identified by multiple regression analysis. The resulting procedure for assessing analytical bias and variability was applied to study in two mutually exclusive cohorts of employees of the Shell petrochemical complex in Rotterdam (a) the true nature of the changes (analytical or biological) in gamma-glutamyltransferase (GGT) and (b) the effect of age on GGT. The first cohort consisted of employees who attended a periodic health assessment in 1984 and in 1989; the second, employees who attended periodic health assessments in 1985 and in 1988. Thus we studied 3- and 5-year changes of GGT corrected for analytical bias. Whereas standard cross-sectional results apparently showed an increase of GGT up to age 50 years, the longitudinal findings corrected for analytical changes, as indicated above, do not support these cross-sectional results.
Kinetics of plasma homocysteine in healthy subjects after peroral homocysteine loading
Authors: Guttormsen A B , Mansoor A M , Fiskerstrand T , Ueland P M , Refsum H
Published: January 2020

The kinetics of plasma homocysteine were determined in 13 healthy subjects after peroral administration and in one person after intravenous injection. Various forms of homocysteine completely dissolved in an aqueous solution were rapidly absorbed after peroral administration, and the bioavailability was estimated to be 0.53. The volume of distribution was 0.66 L/kg. The area under the plasma concentration curve (AUC0-48 h) was proportional to the administered dose (33.5-134 mumol/kg body wt), and showed small interindividual variations. Plasma homocysteine showed first-order elimination kinetics for at least 6 h. The half-life (t1/2) was 223 +/- 45 min, and there was a significant correlation between t1/2 values determined on two different occasions in the same individual. The transient hyperhomocysteinemia was associated with an increase in plasma methionine, which probably reflects intracellular remethylation of homocysteine. Less than 2% of the administered homocysteine dose was recovered in the urine. These findings may form the basis for future studies on the regulation of plasma homocysteine in health and disease, and should motivate the evaluation of a homocysteine loading test as a diagnostic tool.
On the calculation of reference change values, with examples from a long-term study
Authors: Queraltó J M , Boyd J C , Harris E K
Published: January 2020

Reference change values (sometimes called critical differences) indicate statistically important changes between test values obtained on two occasions. They are commonly computed from the median (or mean) within-subject variance observed in repeated test measurements on a number of subjects. With this computational approach, all observed within-subject variances are assumed to be estimates of a constant true variance, the same for all individuals. Moreover, any possible correlation between successive values is almost always ignored. This simplified methodology differs from the method originally proposed for computing reference change values, which accounts for variability in true variances and for serial correlation. From data obtained from repeated measurements over 2 to 5 years in 72 physically healthy subjects, we computed and compared reference change values in 18 serum analytes, using the simplified method and the originally proposed procedure. Although the original method is more complicated and requires a computer program, we believe that it produces more-reliable reference change values than those obtained by the simplified approach. The former are generally larger, but remain sensitive to clinically important changes in the individual.
Desirable standards for laboratory tests if they are to fulfill medical needs
Authors: Fraser C G , Petersen P H
Published: January 2020

Many strategies to define desirable standards for laboratory tests to fulfill medical needs have been proposed over the last three decades. Traditional approaches are based on reference (normal) values, opinions of clinicians, the state of the art, views of experts, data on biological variation, and assessment of the effect of error on clinical use. All these approaches have advantages and disadvantages, but the consensus of experts reached over a decade ago that imprecision desirably be less than one-half of the within-subject biological variation still seems to provide the best set of generally applicable performance standards. Desirable bias is less than one-quarter of the group (within-subject plus between-subject) biological variation. Recent proposals are either restatements of traditional recommendations, further empirical suggestions, or models based on assessment of clinical needs, and have not been widely accepted. Both old and new studies on clinical opinions, sought by using structured questionnaires containing clinical vignettes designed to seek views on the magnitude of significant change, are flawed in design, execution, and data analysis. Until clinicians are more aware of test-result variability and clinical chemists gain quantitative knowledge on the interpretation of test results, it will be difficult to set desirable standards that fulfill actual medical needs, except in a few well-defined screening situations.
Variability of lipid measurements: relevance for the clinician
Authors: Schectman G , Sasse E
Published: January 2020

Decreasing the large test variability associated with measurements of blood cholesterol, triglyceride, and high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)-cholesterol is likely to improve the classification of coronary heart disease (CHD) risk and allow improved monitoring of lipid-lowering treatments. However, improving test precision will benefit the clinician only if (a) the analytical test variability is high relative to the biological test variability and (b) detecting subtle responses to diet or drug therapy is clinically important. Improving HDL- and LDL-cholesterol test precision can be expected to increase the clinical usefulness of these measurements because values for HDL- and LDL-cholesterol correlate closely with CHD risk; are associated with small, yet clinically important, changes in response to diet and (or) drug therapy; and have substantial analytical test variability relative to biological variability. On the other hand, measurements of both blood cholesterol and triglyceride have high biological relative to analytical variability, and do not correlate as closely with CHD risk. Therefore, further improvements in precision for these measurements are less likely to be useful to the clinician.
Medically relevant laboratory-performance goals: a listing of the complexities and a call for action
Authors: Witte D L
Published: January 2020

This 1992 Clinical Chemistry Forum asks if accuracy and precision goals for the laboratory can be specified by reference to medical requirements, which are a function of the total laboratory testing process as well as the needs of patients, clinicians, and societal institutions. Furthermore, medical decisions and decisions about medical requirements must be made in situations of uncertainty and thus are subject to predictable cognitive errors. The interaction of all these factors must be considered by patients, laboratorians, and clinicians to identify practical and effective performance goals. Pathologists and clinical chemists are uniquely trained to identify thoughtful clinicians who are knowledgeable in quantitative judgment to participate in this goal-setting endeavor. It is time for these parties to accumulate the available data and engage in the synthesis of effective performance goals.
Comparison of quality-control rules used in clinical chemistry laboratories
Authors: Bishop J , Nix A B
Published: January 2020

Numerous papers have been written to show which combinations of Shewhart-type quality-control charts are optimal for detecting systematic shifts in the mean response of a process, increases in the random error of a process, and linear drift effects in the mean response across the assay batch. One paper by Westgard et al. (Clin Chem 1977;23:1857-67) especially seems to have attracted the attention of users. Here we derive detailed results that enable the characteristics of the various Shewhart-type control schemes, including the multirule scheme (Clin Chem 1981;27:493-501), to be calculated and show that a fundamental formula proposed by Westgard et al. in the earlier paper is in error, although their derived results are not seriously wrong. We also show that, from a practical point of view, a suitably chosen Cusum scheme is near optimal for all the types and combinations of errors discussed, thereby removing the selection problem for the user.
Estimation of plasma and urinary hemoglobin by a rate spectrophotometric method
Authors: Chalmers A H , Snell L E
Published: January 2020

A method is described for estimating plasma and urinary hemoglobin concentrations as low as 3 mg/L. The assay measures at 528 nm the rate of peroxidation of chlorpromazine by hemoglobin and is not affected by ascorbate and bilirubin concentrations up to 500 mumol/L. Results by this method (mean +/- SD: 54.4 +/- 41.6 mg/L; n = 19) correlated well with those by a scanning spectrophotometric method (52.5 +/- 41.6 mg/L; r = 0.96) and a Coulter Instrument method (r = 0.99; Coulter method: 125 +/- 15 g/L; rate method: 122 +/- 15 g/L; n = 10, r = 0.99). The correlation for assays of 20 plasma samples by our method and a tetramethylbenzidine method was also good (r = 0.95) though the latter gave lower results (31.1 +/- 31.6 mg/L) than the chlorpromazine method (50.9 +/- 41.1 mg/L). The chlorpromazine rate method gave an intra- and interday CV of 7.9% and 9.7%, respectively, at a hemoglobin concentration of 31 mg/L.
Rapid multicomponent analysis of hemoglobin derivatives for controlled antidotal use of methemoglobin-forming agents in cyanide poisoning
Authors: Zijlstra W G , Buursma A
Published: January 2020

When cyanide poisoning is treated with a methemoglobin-forming agent, oxidative metabolism is protected at the expense of the oxygen capacity of the blood. The affinity of methemoglobin for CN- is high enough to compete with cytochrome oxidase, which protects the latter from becoming blocked, but all hemoglobin used for this purpose is lost for the transport of oxygen. Therefore, the fractions of the various hemoglobin derivatives present in the blood should be carefully monitored during this kind of treatment. After we had developed a multiwavelength spectrophotometric method for this purpose, we studied the feasibility of using a modified commercial six-wavelength hemoglobin photometer (Radiometer OSM3) for easy and rapid analysis of methemoglobin and methemoglobin cyanide in small samples of blood. All conditions appeared to be fulfilled for the construction of a practical multiwavelength photometer for reliably monitoring methemoglobin therapy in patients with cyanide poisoning, even in the presence of carboxyhemoglobin, as often occurs in fire victims.
Measurement of carboxyhemoglobin and total hemoglobin by five specialized spectrophotometers (CO-oximeters) in comparison with reference methods
Authors: Mahoney J J , Vreman H J , Stevenson D K , Van Kessel A L
Published: January 2020

We measured total hemoglobin (CtHb) and carboxyhemoglobin (COHb) in 100 patients' blood samples by using five specialized spectrophotometers (CO-oximeters)--IL 482 CO-Oximeter, Corning 2500 CO-oximeter, Radiometer OSM 3 Hemoximeter, Corning 270 CO-oximeter, and the AVL 912 CO-Oxylite--and compared the results with those obtained with the manual cyanmethemoglobin method and a gas-chromatographic (GC) method, respectively. For the CtHb measurements, the differences between the cyanmethemoglobin method and the CO-oximeters were not clinically important for any model. For the blood COHb measurements, the direction of the bias relative to GC was dependent on COHb concentration. In general, the CO-oximeters underestimated COHb concentration for COHb > 2.5% of total hemoglobin but overestimated COHb concentration for COHb < or = 2.5%. We conclude that all five CO-oximeters compared favorably with the reference methods for CtHb and for high concentrations of COHb. However, the inaccuracy of CO-oximeters for low-concentration (< or = 2.5%) COHb measurements may make these instruments unsuitable for some applications.
Within- and between-subject biological variations of follitropin, lutropin, testosterone, and sex-hormone-binding globulin in men
Authors: Valero-Politi J , Fuentes-Arderiu X
Published: January 2020

The within-subject and between-subject biological variation of the serum concentrations of follitropin, lutropin, sex-hormone-binding globulin, and testosterone; the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin; and the concentration of testosterone in saliva have been studied in a group of 20 men during 12 months. The between-subject coefficients of variation (CVs) were 36.0% for follitropin, 37.0% for lutropin, 42.7% for sex-hormone-binding globulin, 21.3% for testosterone in serum, 28.8% for testosterone in saliva, and 51.6% for the ratio between serum concentrations of testosterone and sex-hormone-binding globulin. The medians of the within-subject CVs for the respective analyses and ratio were 17.3%, 24.0%, 12.1%, 10.9%, 17.3%, and 9.4%. These data were used to calculate the desirable imprecision, the critical difference for significant change detection, and the index of individuality.
Factitious hyperthyroxinemia due to a monoclonal IgA in a case of multiple myeloma
Authors: Cissewski K , Faix J D , Reinwein D , Moses A C
Published: January 2020

A clinically euthyroid 53-year-old woman with an IgA-lambda-secreting multiple myeloma presented with increased serum concentrations of thyroid hormones. Laboratory studies revealed increased total thyroxine (T4) and triiodothyronine (T3) concentrations, a high-normal free T4 concentration, and a normal basal thyrotropin (TSH) concentration with a normal response to thyroliberin (TRH). Her serum concentration of IgA was 11,040 mg/L (normal range 900-4500 mg/L) and immunoelectrophoresis revealed it to be monoclonal. This monoclonal IgA bound both T4 and T3, as determined by serum immunoelectrophoresis and direct binding studies. Immunoelectrophoresis in the presence of [125I]T4 or [125I]T3 localized the radiolabeled iodothyronines to a band corresponding exactly to the precipitin arc of the monoclonal IgA. We performed direct binding studies with IgA purified by affinity chromatography with the lectin jacalin. Purified IgA (50 micrograms) bound both [125I]T4 (12.3%) and [125I]T3 (2.7%) specifically and in a dose-dependent manner. Scatchard analysis of competitive-binding data utilizing [125I]T4 and unlabeled T4 revealed a Kd of 2.2 x 10(-7) mol/L. The binding capacity for T4 was approximately 7 mumol/L. Thus, in this case of IgA-secreting myeloma, the monoclonal IgA acts as an additional thyroid hormone-binding protein in serum that interferes in the T4 and T3 RIAs. This is the first report of a monoclonal IgA producing an apparent euthyroid hyperthyroxinemia.
Total homocysteine in plasma or serum: methods and clinical applications
Authors: Ueland P M , Refsum H , Stabler S P , Malinow M R , Andersson A , Allen R H
Published: January 2020

Total homocysteine is defined as the sum of all homocysteine species in plasma/serum, including free and protein-bound forms. In the present review, we compare and evaluate several techniques for the determination of total homocysteine. Because these assays include the conversion of all forms into a single species by reduction, the redistribution between free and protein-bound homocysteine through disulfide interchange does not affect the results, and total homocysteine can be measured in stored samples. Total homocysteine in whole blood increases at room temperature because of a continuous production and release of homocysteine from blood cells, but artificial increase is low if the blood sample is centrifuged within 1 h of collection or placed on ice. Different methods correlate well, and values between 5 and 15 mumol/L in fasting subjects are considered normal. Total homocysteine in serum/plasma is increased markedly in patients with cobalamin or folate deficiency, and decreases only when they are treated with the deficient vitamin. Total homocysteine is therefore of value for the diagnosis and follow-up of these deficiency states and may compensate for weaknesses of the traditional laboratory tests. In addition, total homocysteine is an independent risk factor for premature cardiovascular diseases. These disorders justify introduction of the total homocysteine assay in the routine clinical chemistry laboratory.
Characterization and mathematical correction of hemolysis interference in selected Hitachi 717 assays
Authors: Jay D W , Provasek D
Published: January 2020

The effect of hemolysis on several assays performed with the Hitachi 717 was quantified by relating the amount of error to the concentration of hemoglobin. Hemolysis interference was judged clinically significant when analyte concentration varied by > 10% from the initial value. Hemolysis interference was significant for alkaline phosphatase, aspartate aminotransferase, alpha-amylase, bilirubin, creatine kinase, gamma-glutamyltransferase, lactate dehydrogenase, lactate dehydrogenase-1, potassium, and theophylline assays. Error (expressed in absolute terms) was linearly dependent on hemoglobin concentration and independent of the initial analyte concentration in each case, except for bilirubin and theophylline, where multiple regression analysis was required to quantify the effect. Relative error was dependent on the initial analyte concentration in all cases. Correction formulas were calculated from linear regression of absolute error vs hemoglobin concentration. Clinical application of correction formulas and mechanisms of hemolysis interference for each assay are discussed.
Unusual thermolability properties of leukocyte beta-hexosaminidase: implications in screening for carriers of Tay-Sachs disease
Authors: Prence E M , Natowicz M R , Zalewski I
Published: January 2020

Tay-Sachs disease (TSD), an autosomal recessive neurodegenerative condition, is the result of a deficiency of beta-hexosaminidase A (hex A). Heterozygotic individuals are screened by analysis for hex A and hex B activities; the percent of hex A is the critical determinant of carrier vs noncarrier status. Most laboratories use a heat-inactivation assay that exploits the differential thermolability of the isoenzymes. However, we have found a reciprocal relation between the apparent leukocyte hex A activity and the amount of the sample used in the assay; i.e., a significant increase in the percent of hex A activity with decreasing amounts of sample. Three sets of data indicate that this phenomenon was caused by an effect on the hex B isoenzyme and not on hex A. This variation in hex A activity with sample amount was not observed when a hex A-specific substrate was used. This phenomenon was also not seen in assays of leukocytes from carriers for Sandhoff disease, a condition associated with a reduction in the amount of hex B. Finally, when leukocytes from a TSD homozygote, containing almost no hex A, were analyzed, marked increases in the percent of hex A were observed with decreasing sample concentrations. These data indicate that misdiagnoses could result from variations in sample concentrations used for TSD carrier testing and support the view that the leukocyte concentrations used for these assays should be standardized.
Urinary metanephrine and normetanephrine determined without extraction by using liquid chromatography and coulometric array detection
Authors: Gamache P H , Kingery M L , Acworth I N
Published: January 2020

We describe a procedure for the direct measurement of metanephrine (MN) and normetanephrine (NMN) in hydrolyzed urine, using HPLC with coulometric array detection. Acid-hydrolyzed samples were diluted and filtered before separation by isocratic reversed-phase ion-pair chromatography. Eight serial coulometric sensors, set at incrementally increasing anodic potentials, were used to screen lower-oxidizing interferences and provide stepwise oxidation of the metanephrines. Voltammetric behavior across three adjacent sensors was used to assess resolution and aid in peak identification. Values obtained in commercial controls were consistently within the specified target range. Variability, expressed as CV, was 5.45-9.22% between runs and 1.60-4.52% within-run for both compounds. The limit of detection was 2.6 micrograms/L for MN and 2.8 micrograms/L for NMN, with a linear response to 15.0 mg/L for both analytes. Results from patients' samples correlated well with those by a method involving dual ion-exchange extraction (r = 0.963, n = 82 for MN; r = 0.9768, n = 83 for NMN). This procedure provided high selectivity and objective peak purity information while greatly simplifying sample preparation.
Interference in immunoassay measurements of total and free phenytoin in uremic patients: a reappraisal
Authors: Roberts W L , Rainey P M
Published: January 2020

Accumulation of phenytoin metabolites in uremia has been shown to interfere with some immunoassay methods for phenytoin measurement. We evaluated the effects of uremia (serum creatinine > 13 mg/L) on free and total phenytoin concentrations measured by the Abbott TDx fluorescence polarization immunoassay, and the DuPont aca and Syva EMIT homogeneous enzyme-multiplied immunoassay methods, using HPLC as the comparison method. In uremic patients, the TDx assay showed both fixed and proportional bias in comparison with the HPLC for both total phenytoin concentration (TDx = 1.24 x HPLC + 1.9 mg/L) and free phenytoin concentration (TDx = 1.52 x HPLC + 0.24 mg/L). The total bias was as great as 100% for both total and free phenytoin. Cross-reactive substances other than 5-(p-hydroxyphenyl)-5-phenylhydantoin (HPPH) and HPPH-glucuronide appeared to be responsible. In contrast, there was minimal interference with aca and EMIT assays.
Reference standards for quantification of skeletal alkaline phosphatase activity in serum by heat inactivation and lectin precipitation
Authors: Farley J R , Hall S L , Herring S , Libanati C , Wergedal J E
Published: January 2020

Putative standards of skeletal alkaline phosphatase (ALP) (from bone, bone cells, osteosarcoma cells, and Pagetic serum) and hepatic ALP (from cholestatic serum and bile) were used to compare three methods for quantifying skeletal ALP activity in serum: heat inactivation, precipitation with wheat germ agglutinin (WGA), and precipitation with concanavalin A (Con A). All the skeletal ALP standards were similarly sensitive to heat inactivation, as were the hepatic ALP standards. Heat inactivation separated skeletal from hepatic ALP by a 50% difference in remaining ALP activities (e.g., 23% and 74% remaining skeletal and hepatic ALP activities after 30 min at 52 degrees C). Differential precipitations with WGA and with Con A were less efficient at separating skeletal from hepatic ALP (maximum differences of < 30% remaining ALP activity). Although both types of hepatic ALP standard (cholestatic serum and bile) were precipitated with similar efficiencies by WGA and Con A, the skeletal ALP standards were not (e.g., at 2.7 g/L, WGA precipitated 78-86% of the ALP activity in Pagetic serum, but only 49% of the ALP activity in extracts of human bone). These data suggest that heat inactivation is preferable to precipitation with WGA or Con A for quantifying skeletal ALP activity in serum: it better separates skeletal from hepatic ALP activity and is not sensitive to glycosyl heterogeneity.
Severe isopropanolemia without acetonemia or clinical manifestations of isopropanol intoxication
Authors: Chan K M , Wong E T , Matthews W S
Published: January 2020

This is the first reported case of severe isopropanolemia in a patient who did not experience associated clinical manifestations and acetonemia. The patient was found lying face down in a hotel lobby but at admission was alert and oriented to place and person. Toxicological analysis of the patient's serum revealed the presence of isopropanol at a concentration of 72 mmol/L. An increased serum osmolal gap (81 mOsm/kg) was also observed. The serum concentration of isopropanol decreased to 9.5 mmol/L 15.5 h after admission with an estimated half-life of elimination of 5-7 h. No serum acetone was detected throughout the patient's hospitalization. The identity of isopropanol was confirmed by gas chromatography/mass spectrometry. The patient remained awake and alert while in the hospital and was discharged 5 days after admission. These unusual findings raise some fundamental questions about the role of isopropanol conversion to acetone in the manifestation of symptoms usually associated with isopropanol intoxication.
Mass spectrometry of proteins and peptides: sensitive and accurate mass measurement and sequence analysis
Authors: Arnott D , Shabanowitz J , Hunt D F
Published: January 2020

The study of proteins and peptides by mass spectrometry has been advanced by the development of matrix-assisted laser desorption/ionization and electrospray ionization. Proteins with masses > 100 kDa may be measured accurately at picomole sensitivities. Sequence analysis of peptides in mixtures at subpicomole quantities is possible by tandem mass spectrometry. Practical applications of the new technology to biological research are illustrated.
224 Malignancy associated pericardial effusion- do we need to drain them all?
Authors: Ho C , Lee P H , So T C , Chiang M C S , Wong M H , Fong Y H , Tsang C F , Cheng Y W , Luk N H , Chui S F , Chan K C , Wong C Y , Fu C L , Lee K Y , Chan K T
Published: January 2020

On Behalf

Cardiac Team, Department of Medicine, Queen Elizabeth Hospital

Background

Management of significant pericardial effusion in cancer patients is controversial. These patients have poor prognosis, and avoiding unnecessary intervention is important. Close monitoring of symptoms and echocardiogram is often a reasonable option, but inherits risk of cardiac tamponade. Whether pericardial drainage by means of percutaneous pericardiocentesis or surgical pericardiotomy could prevent future deterioration or affect survival is unknown.

Purpose

To evaluate the benefit of elective pericardial drainage in malignancy associated pericardial effusion without echocardiographic or clinical evidence of tamponade effect.

Methods

From 1st Jul 2014 to 31st Dec 2017, all patients with new onset malignancy-associated pericardial effusion with size more than 1cm were retrospectively analyzed. Patients with clinical or echocardiographic evidence of cardiac tamponade were excluded. We compared pericardial drainage versus monitoring for short-term (30-day), mid-term (90-day) and long term (1 year) survival without need for drainage.

Results

101 patients were retrospectively analyzed. 40 (39.6%) patients underwent drainage. Overall median survival free from drainage was 4 months. There were no significant difference in short-term (30-day), mid-term (90-day) and long term (1-year) survival free from drainage or mortality between treatment and monitoring group. Size of pericardial effusion did not predict mortality or future need of drainage. Chemotherapy was associated with improved 30-day mortality (RR 0.53 CI 0.32-0.87 p = 0.025) but not survival free from drainage or longer term mortality.

Conclusion

Close monitoring could be a feasible strategy in cancer patients with significant pericardial effusion without tamponade effect.

Baseline characteristics Factor Drainage (n = 40) monitoring (n = 61) p-value method of drainage pericardiocentesis alone 17 NA pericardiotomy alone 13 both 10 Male 19 (47.5%) 27 (44.3%) 0.749 mean size (cm) 1.93 2.77 <0.001 mean age 60.9 63.1 0.357 on chemotherapy 27 (67.5%) 38 (62.3%) 0.593

Abstract 224 Figure. Survival free from drainage
P24 Association between plasma PCSK9 and major cardio-cerebrovascular events in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention
Authors: Santoso A , Nofanda Putra A , Arifa Yuzar D A F S A H
Published: January 2020

Background

Some STEMI patients still suffers adverse outcomes though they undergo optimal management, including primary PCI. Plasma PCSK9 is deemed to  have a role in that residual risk. Our knowledge on the association between plasma PCSK9 level and MACCE in STEMI is still limited.

Purpose

The aim of this study is to evaluate the association between plasma PCSK9 level during admission with MACCE in STEMI who undergo primary PCI.

Methods

This was a prospective observational study, recruited 239 patients with STEMI who were treated with primary PCI and assayed for PCSK9 level using ELISA technique.  MACCE and other supportive data were taken from the medical records and telephone follow-up.

Results

 There were 28 study participants who experienced MACCE in 30 days. However, survival analysis did not show a significant association between plasma PCSK9 level and MACCE in 30 days. The hazard ratio for MACCE between the third tertile and the second tertile of plasma PCSK9 level was 1.466 (95%CI 0.579-3.714) and between the first tertile and the second tertile was 1.257 (95%CI 0.496-3.185).

Conclusion

 Plasma PCSK9 levels was not associated with MACCE in STEMI patients treated with primary PCI.
P42 Role of statins for the prevention of anthracycline-induced cardiomyopathy: a meta-analysis
Authors: Reymatias J , Villanueva D L , Ramiro V , Magno J D
Published: January 2020

Background

 Anthracyclines are key components of many chemotherapeutic regimens, having demonstrated efficacy in lymphomas and many solid tumors. However, a major factor limiting their use is a cumulative, dose-related cardiotoxicity which ultimately leads to asymptomatic and symptomatic heart failure. Oxidative stress is considered as a major mechanism in anthracycline-induced cardiomyopathy. Statins have been shown to possess anti-oxidative, pleiotropic effects besides their anti-inflammatory and lipid-lowering effects.

Purpose

 This study evaluated the potential role of statin for the prevention of anthracycline-induced cardiomyopathy.

Methods

 Using MEDLINE, EMBASE, ScienceDirect, Scopus, Google Scholar, ClinicalKey, Cochrane Database of Systematic Reviews, clinicaltrials.gov, and Cochrane Central Register of Controlled Trials databases, a search for eligible studies was conducted until December 2018. Included studies were evaluated based on the Cochrane Collaboration"s tool for assessing risk of bias. Our primary outcome of interest was the development of anthracycline-induced cardiomyopathy. We also investigated the mean change in LVEF pre- and post-chemotherapy with anthracycline. Review Manager (RevMan) 5.3 was utilized to compute for relative risk and mean change in LVEF. A random effects model was applied for all meta-analyses.

Results

 We identified 3 studies involving 332 cancer patients, showing that in cancer patients undergoing anthracycline-based chemotherapy, pre-treatment with statins was associated with a lower risk of developing anthracycline-induced cardiomyopathy (RR 0.33, 95% CI 0.14-0.79, p < 0.05). There was a significant decrease in LVEF among patients who were not treated with statins [Mean difference -6.25, 95% CI -11.68 - (-) 0.82, p= 0.02]

Conclusions

 Pre-treatment with statins on cancer patients undergoing anthracycline chemotherapy may prevent the development of anthracycline-induced cardiomyopathy and reduction in LVEF. This will expand the utility of statin as a medication for the prevention and treatment of cardiovascular diseases.
P104 Prognostic value of Circulating Amino Acids (AAs) in Patients with Idiopathic Dilated Cardiomyopathy (DCM)
Authors: Wakasa M , Kawai Y , Kajinami K
Published: January 2020

Backgrounds Circulating levels of some amino acids are significantly decreased in heart failure patients. However, relationship between their levels and cardiac function remains unclear. We therefore examined association between amino acid levels and cardiac function as prognostic predictor in DCM patients.

Methods

Consecutive 59 patients with DCM (M/F: 46/13, mean age: 59 years) were enrolled. We measured 25 kinds of plasma AA concentration, derivative of reactive oxygen metabolites (d-ROMs) as marker of oxidative stress, and washout rate of Tc-99m Sestamibi (WOR) as function of mitochondria and LVEF as LV function parameters. The occurrence of rehospitalization for cardiac events or cardiac death were followed during mean 1101 days (13-2626).

Results

Histidine, arginine and Fischer ratio (FR) showed a significant positive association with LVEF (p < 0.05). Threonine and asparagine showed a significant negative association with WOR (P < 0.05). Histidine and arginine showed a significant negative association with levels of d-ROMs (p < 0.05).Rehospitalization for cardiac events and cardiac death were recorded in 16 patients (27%) and 6 patients (10%), respectively. Kaplan-Meier curves analysis showed similar trend of rehospitalization in subjects with lower FR and those with higher values. However, cardiac death in subjects with lower FR was observed more frequently as compared to those with higher values (22.2% vs 5.3% p < 0.05).

ConclusionsThe plasma FR could be a novel prognostic biomarker in DCM patients.
P119 The impact of minimal alcohol price policy on premature CVD mortality in Kazakhstan
Authors: Davletov K , Mereke A , Tussupbekova S , Tolegenova A
Published: January 2020

Background

In Kazakhstan, premature cardiovascular (CVD) mortality is one of the highest in the world despite the dramatic decline of CVD mortality since 2006.  Our previous research found that alcohol consumption was the main determinant of premature CVD mortality in Kazakhstan and the decrease of alcohol use was the main factor influencing the CVD mortality decline.

Purpose

With the aim of examining the impact of minimal price changes for strong spirits (vodka) and alcohol sales on premature CVD mortality in 2006-2014, we compared age-specific CVD mortality for the age group 19-49 with changes in the minimal price of strong spirit (vodka) and alcohol sales.

Methods

Age-specific CVD mortality rates in age group 19-49 in Kazakhstan were obtained from the Global Burden of Disease database and explored with regard to changes in minimal prices of vodka and alcohol sales in Kazakhstan over this period.

Results

Age-standardized CVD mortality rates in age group 19-49 declined by 47% from 2006 to 2014, for both men and women.  However, we observed the plateauing effect in CVD mortality trend in 2015-2017. These mortality trends coincided with the sharp increase in minimal vodka prices and decrease or flatten in alcohol sales in 2006-2014 period and consequent minimal price decrease and plateauing in 2015-2017 that was accompanied by increase of alcohol sales in this period.

Conclusions

Our findings indicate that public health measures such as tax increases for strong spirits can be a very effective CVD prevention strategy in Kazakhstan and other former USSR countries, where similar mortality trends can be observed. Unfortunately, this mortality decline was not sustained over time. We believe it happened due to a weakened policy in regard to the minimal alcohol prices.  Therefore, there is much scope for further policy action in this area.

Abstract P119 Figure. CVD and Alcohol price