bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lidocaine metabolite and creatinine measurements in the Ektachem 700: steps to minimize its impact on patient care.
Authors: Sena S F , Syed D , Romeo R , Krzymowski G A , McComb R B 
Published: January 2020

Abstract
The single-slide method used for creatinine in the Kodak "Ektachem" analyzer is far more precise than the two-slide method. We confirm that sera from patients on intravenous therapy with lidocaine exhibit a positive bias in results for creatinine but that lidocaine itself does not interfere. Instead, N-ethylglycine, a metabolite of lidocaine with a structure similar to that of sarcosine, is probably the cause. A method that allows N-ethyglycine to be measured directly is described. We followed the degree of this interference through five generations of the slide. Our investigations include two detailed comparison studies between the Kodak Ektachem 700 and the Beckman Astra analyzers. Creatinine determinations on lidocaine-treated patients when first-generation slides were used averaged 4.6 mg/L higher than determinations on these same specimens performed in the Astra. Serum creatinine results from patients not on lidocaine showed no significant difference between the two instruments. The average difference in generation 2, 3, and 4 slides was 0.24, 0.22, and 2.5 mg/L, respectively. No more than 2% of our creatinine results had a clinically significant lidocaine-related bias. We show how to identify and correct this small proportion of results that are biased because of lidocaine therapy.
Disposable-column radioimmunoassay for serum digoxin with less interference from metabolites and endogenous digitalis-like factors.
Authors: Longerich L , Vasdev S , Johnson E , Gault M H 
Published: January 2020

Abstract
A preparative extraction step using disposable C18 low-pressure chromatography columns greatly improved the specificity of a commercially prepared digoxin radioimmunoassay (RIA). Elution solvents were isopropanol/water (15/85 by vol), which extracted most immunoreactive digitalis-like factors and metabolites, and methanol, which extracted digoxin for RIA. Many different digoxin RIA kits could be used. The coefficients of variation for replicates and duplicates were 4.6% and 5.2%. Analytical recoveries of digoxin standards in serum of 1.0, 0.5, and 0.1 microgram/L were 96%, 95%, and 88%, respectively. Serum digoxin was assayed by this method in 200 patients, 47 of whom were studied by HPLC-RIA. Values correlated better with "true digoxin" by HPLC-RIA (r = 0.93) than did values found by direct assay (r = 0.63). The mean for the isopropanol fraction as a percentage of the mean direct RIA value was higher for the 21 dialysis-dependent patients than was that found for the 179 nondialysis patients (P less than 0.004). The method is suggested as being most useful when metabolites or digitalis-like factors are known to be often high and values for digoxin are disproportionate to the dose.
Determination of vanillylmandelic acid, vanillactic acid, and homovanillic acid in dried urine on filter-paper discs by high-performance liquid chromatography with coulometric electrochemical detection for neuroblastoma screening.
Authors: Kinoshita Y , Yamada S , Haraguchi K , Takayanagi T , Mori Y , Takahashi T , Haruki E 
Published: January 2020

Abstract
We report a method for determination of vanillylmandelic acid, vanillactic acid, and homovanillic acid by high-performance liquid chromatography (HPLC), with coulometric electrochemical detection, for mass screening of neuroblastoma. Urine samples were collected on filter paper, dried, and then pretreated. The chromatographic procedure is reliable and fast, allowing for a large sample throughput for routine screening. Intricate extraction procedures and centrifugal separation are unnecessary. Screening for neuroblastoma by HPLC is rapidly gaining acceptance in Japan, and our method is being used at many screening centers. Of 26,571 infants screened in one year in Yokohama City, our method detected five with neuroblastoma.
Liquid-chromatographic measurement of p-aminobenzoic acid and its metabolites in serum.
Authors: Yung-Jato L L , Durie P R , Soldin S J 
Published: January 2020

Abstract
This is a high-performance liquid-chromatographic method for measuring p-aminobenzoic acid (PABA) and its metabolites in plasma or serum. Samples are deproteinized, then extracted with organic solvents before chromatography. For quantification, the peak height of the individual compound is compared with that of the internal standard. Analytical recoveries ranged from 41% to 100%, depending on the compound studied. Comparison of patients' samples after oral administration of either N-benzoyl-L-tyrosyl-p-aminobenzoic acid or free PABA revealed that PABA is extensively metabolized and conjugated to either p-acetamidobenzoic acid, p-aminohippuric acid, or p-acetamidohippuric acid. PABA concentrations in serum as measured with the Bratton-Marshall ultraviolet spectrophotometric procedure would appear predominantly to reflect measurements of metabolites, with only a minor contribution from PABA itself.
Homogeneous time-resolved fluoroimmunoassay of thyroxin in serum.
Authors: Hemmilä I , Malminen O , Mikola H , Lövgren T 
Published: January 2020

Abstract
We describe a rapid, simple nonseparation fluoroimmunoassay for determination of thyroxin in serum. The assay is based on the labeling of thyroxin directly with a fluorescent europium chelate, the fluorescence of which is quenched on binding to an antithyroxin antibody. With the assay buffer we used, maximum quenching is 90%. The rapid achievement of equilibrium in the assay solution, regardless of the sequence of reagent additions, allows fast measurement of thyroxin. Precision was good (CV less than 5%) within the clinical range for total thyroxin (50-300 nmol/L), and results correlated well with those by a commercial radioimmunoassay.
Determination of D-sorbitol in human erythrocytes by an improved enzymatic method with fluorometric detection.
Authors: Liao J C , Rountree M , Good R , Hook J , Punko C 
Published: January 2020

Abstract
In this enzymatic method to analyze erythrocytes for D-sorbitol, the erythrocytes were separated from plasma by centrifugation, washed with isotonic saline (9 g/L NaCl), then diluted threefold with more saline. We lysed 1.5 mL of the diluted erythrocytes with chloroform and precipitated the protein with 58 g/L HClO4 solution. The resulting supernates were mixed with buffer, NAD+, and sorbitol dehydrogenase (EC 1.1.1.14). For standards, we added sorbitol to the erythrocytes before lysing. After 25 min of incubation at 37 degrees C, the fluorescence responses were recorded. Results for sorbitol were corrected for sample-blank and enzyme fluorescence, and were then normalized for hemoglobin content. Response was linear for a sorbitol concentration range of 1 to 30 mumol/L. Reproducibility was good, with an average CV of 2.5% at 10 mumol/L. Results for healthy individuals and diabetic patients are presented.
Evaluation of the Technicon Chem-1.
Authors: Barlow I M , Harrison S P , Hogg G L 
Published: January 2020

Abstract
We evaluated the performance of 15 colorimetric and three ion-selective electrode assays in the Technicon Chem-1 serum analyzer and briefly assessed the suitability of plasma and urine for analysis in the system. Within- and between-batch precision, accuracy, correlation, and linearity of all methods was acceptable but some assays, notably those for bicarbonate and creatinine, were susceptible to interferences. Except for the total bilirubin and lactate dehydrogenase assays, plasma can be assayed successfully in the instrument. Urine samples can also be assayed but specimens for phosphate analysis must be diluted in a polyvinylpyrrolidone solution before analysis, and the calcium method is sensitive to variations in urinary pH.
A simple liquid-chromatographic method applied to determine caffeine in plasma and tissues.
Authors: Biaggioni I , Paul S , Robertson D 
Published: January 2020

Abstract
In this simple, reliable assay for quantifying caffeine in plasma and tissues, methylxanthines are first partly purified from plasma and acid extracts of tissue by passage through solid-phase columns. The ease of this extraction method permits a relatively large number of samples to be processed daily. Quantification is by reversed-phase high-pressure liquid chromatography (mobile phase: acetic acid/acetonitrile/water, 2/6/92 by vol). Caffeine is eluted in 20 min. The reliability of this method allows its automation. This method has been adapted to measure caffeine in brain and kidney extracts and in as little as 10 microL of plasma. After 10 days of oral administration of caffeine (1 g/L, in drinking water) to six rats, the mean (+/- SEM) concentrations of caffeine in plasma, brain, and kidney were 18.6 +/- 6.0 micrograms/mL, 16.2 +/- 1.5 micrograms/g, and 18.9 +/- 2.0 micrograms/g, respectively. Correlations were linear between concentrations of caffeine in plasma and brain (r = 0.86) and between concentrations in plasma and kidney (r = 0.91). This method should be useful in studying the effects and mechanisms of actions of methylxanthines.
Libyan family with beta-thalassemia trait associated with hypercholesterolemia with widespread xanthomas.
Authors: Sheriff D S , el Fakhri M 
Published: January 2020

Abstract
We describe a Libyan family with beta-thalassemia trait associated with unusually high concentrations of hemoglobin A2 and hypercholesterolemia. The family consists of the father, mother, and three sons. The marriage was consanguineous. The concentrations of total cholesterol and low-density lipoprotein cholesterol in serum were very high in two sons who also had widespread xanthomas. The erythrocyte membranes showed a high cholesterol/phospholipid ratio, with no significant susceptibility to lipid peroxidation in vitro.
Free triiodothyronine measured in dried blood spots from normal, low-birth-weight, and hypothyroid neonates.
Authors: Laroche D , Lemonnier F , Viel J F , Travert G , Fernandez Y 
Published: January 2020

Abstract
Free triiodothyronine (FT3) has rarely been studied in neonates, primarily because of obvious problems in obtaining serum samples from neonates for research purposes. We adapted an analog radioimmunoassay for measuring FT3 in dried blood samples and used it to assay 361 samples selected from those collected for the screening for neonatal hypothyroidism. The mean FT3 concentration in healthy neonates on the fourth postpartum day is 2.55 pmol per liter of whole blood (SD 0.78 pmol/L, n = 145), the same as in healthy adults. Low-birth-weight infants have a decreased concentration of FT3, and this decrease is much greater in premature neonates than in infants at low weight for gestational age. In six hypothyroid newborns, the FT3 concentration was normal or increased, clearly indicating that FT3 assay is not a diagnostic tool for hypothyroidism. FT3 was barely detectable in one case of congenital galactosemia.
An enzyme immunoassay procedure for cancer antigen 125 evaluated.
Authors: Ryder K W , Oei T O , Hull M T , Sample M M 
Published: January 2020

Abstract
The performance of a new enzyme immunoassay (EIA) procedure (Abbott Labs.) for cancer antigen 125 (CA 125) met or exceeded the manufacturer's claims for all analytical variables examined. Overall correlation with results obtained with a radioimmunoassay (RIA) were good. However, near the decision thresholds typically chosen to define a positive result for ovarian carcinoma, EIA results were 10 to 20 arbitrary units/mL less than the RIA results. At specific decision thresholds, therefore, the sensitivities and specificities of the EIA and RIA procedure differed. Adjusting the decision thresholds gave a similar optimum efficiency for each procedure: EIA, 82.9% (decision threshold, 35 units/mL); RIA, 83.4% (decision threshold, 54 units/mL). Receiver-operating characteristic curves showed that the two procedures' ability to distinguish patients with active ovarian carcinoma from those with disease in remission was the same.
Reflotron cholesterol measurement evaluated as a screening technique.
Authors: Sedor F A , Holleman C M , Heyden S , Schneider K A 
Published: January 2020

Abstract
We evaluated the analytical performance of Boehringer Mannheim Diagnostics' "Reflotron" analyzer for the measurement of cholesterol. Coefficients of variation (CVs) for whole-blood cholesterol were: within-day 2.0% and 2.2% at 1680 and 2670 mg/L, respectively; between-day 1.8% and 2.4% (n = 9 and 8). Results were similar for serum and heparinized or EDTA-treated single-donor plasma (CV 1.4% to 2.6%). CVs of results for two reconstituted commercial quality-control materials were 3.4% and 4.6%. Heparin and hematocrit were evaluated as interferents, and critical limits for interference were identified for bilirubin, hemoglobin, and triglyceride in blood and plasma or serum. When sample collection and analysis were controlled by trained personnel, results with the Reflotron (y) compared well with those by the Ektachem procedure (x) for both blood and serum samples: r = 0.950, y = 0.944x + 130 mg/L; and r = 0.955, y = 0.93x + 43.5 mg/L, respectively. The same comparability was observed when the analysis was performed by briefly trained high-school students: r = 0.980, y = 0.949x + 23 mg/L. Performance decreased when both collection and analysis were performed by laymen: r = 0.880, y = 0.870x + 186 mg/L.
Stability of serum fructosamine during storage.
Authors: Koskinen P , Irjala K 
Published: January 2020

Abstract
Stability of serum fructosamine during storage was evaluated in serum specimens obtained from 27 diabetic individuals. The samples were divided into six aliquots, which were stored at -20 degrees C and -70 degrees C for two, eight, and 16 months. The minor systematic differences between the six treatments contrasted with the considerable variation of individual specimens. The mean percentage changes in the six treatments ranged between -4.6% and 7.5%, whereas the changes in individual specimens ranged from -20% to 26.7%. Several factors evidently contribute to this variation, one being progressive in vitro glycation, especially at -20 degrees C. Small changes in fructosamine concentrations between consecutively drawn specimens, determined after storage, evidently should be interpreted cautiously. Low temperatures, at least -70 degrees C, are preferable to minimize pre-analytical variation during storage.
Definitive liquid-chromatographic demonstration that N-ethylglycine is the metabolite of lidocaine that interferes in the Kodak sarcosine oxidase-coupled method for creatinine.
Authors: Roberts R T , Alexander N M , Kelner M J 
Published: January 2020

Abstract
Patients receiving lidocaine may show false increases of serum creatinine as assayed by the single-slide method on the Kodak Ektachem 700. Bissell et al. (Clin Chem 1987;33:951) suggested that this interference was due to oxidation of N-ethylglycine (NEG), a previously uncharacterized metabolite of lidocaine, by the sarcosine oxidase preparation used in the Ektachem creatinine slide. To investigate this possibility, we synthesized NEG, added it to drug-free human serum, and analyzed the NEG-supplemented sera for creatinine with the Ektachem 700. We found the following linear relationships between creatinine bias (y, mg/L) and NEG concentration (x, mg/L) for first (I), third (III), and fourth (IV) generation slides: I: y = 1.70x - 0.8 mg/L (n = 13, r = 1.0) III: y = 0.39x - 0.3 mg/L (n = 3, r = 1.0) IV: y = 0.79x - 1.8 mg/L (n = 13, r = 1.0) Using HPLC, we directly demonstrated the presence of NEG in sera of patients receiving lidocaine and quantified NEG concentrations in sera from four of these patients. The increasing artifactual bias in creatinine with increasing NEG concentration unequivocally confirmed that NEG is responsible for the lidocaine-associated interference in the Kodak Ektachem single-slide creatinine method.
Concentrations of serotonin in plasma--a test for appendicitis?
Authors: Singh S M , Dean H G , de Dombal F T , Wilson D H , Flowers M W 
Published: January 2020

Abstract
We assessed the value of measuring serotonin (5-hydroxytryptamine) in plasma (by HPLC) in the diagnosis of acute appendicitis. Values for patients with subsequently confirmed appendicitis (11-145 nmol/L, median 70 nmol/L) significantly (P congruent to 0.005) exceeded those for patients with abdominal pain in whom appendicitis was only a possible diagnosis (2-45 nmol/L, median 20 nmol/L). The results for appendicitis patients were bimodally distributed, with low results found in patients where surgery revealed gangrenous appendicitis with little viable appendicular tissue. We conclude that measuring serotonin may be of value in confirming or excluding the diagnosis of early acute appendicitis where the physical signs are equivocal, and thus helps reduce unnecessary appendectomies. However, serotonin is of little help in diagnosing gangrenous appendicitis, where physical signs are more likely to be clearcut.
Escape from blockade of interfering heterophile antibodies in a two-site immunoradiometric assay for thyrotropin.
Authors: Zweig M H , Csako G , Spero M 
Published: January 2020

Abstract
Sandwich-type immunoassays in which mouse monoclonal antibodies are used are subject to positive interference by heterophile antibodies present in human serum. Manufacturers now customarily add nonspecific mouse immunoglobulins to absorb the heterophile antibodies and eliminate such interference. We describe the case of a patient who had spurious increases in thyrotropin concentration in serum despite use of the mouse immunoglobulins included in the assay kit. This resulted in a puzzling clinical picture, a workup, and treatment. We demonstrate that the observed increases in thyrotropin were markedly reduced by including additional amounts of mouse immunoglobulins of the appropriate class, subclass, and fragment type in the assay mixture.
Lactulose interferes in the alkaline picrate assay for creatinine.
Authors: Bruns D E 
Published: January 2020

Abstract
Errors of more than 10 mg/L in measured serum creatinine concentrations were encountered for an azotemic patient who was given lactulose orally. The magnitude of the apparent error fluctuated with the dose of lactulose. Additions of lactulose to serum produced a linear increase in the creatinine measured by each of two automated methods that involve use of the alkaline picrate (Jaffé) reaction. A lactulose concentration of 100 g/L produced positive interferences of 30 and 65 mg/L in kinetic (Beckman Astra) and continuous-flow (Technicon SMAC) assays, respectively, but caused no problem in an enzymatic assay for creatinine. The results of creatinine assays must be interpreted with caution in patients treated with lactulose.
Use of alternative rules (other than the 1(2)s) for evaluating interlaboratory performance data.
Authors: Ehrmeyer S S , Laessig R H , Schell K 
Published: January 2020

Abstract
Previous studies have documented the ineffectiveness of using either the group mean +/- 2 group standard deviations (SD) or the 1(2)s rule as the standard of acceptable performance in evaluating interlaboratory proficiency testing (PT) data. Using computer simulation of PT data, we evaluated the efficiency of 244 alternatives to the 1(2)s rule, all based on the PT population's mean and SD. Using the traditional interlaboratory PT format, we determined the ability of each rule to correctly identify both good and deficient intralaboratory performance. The rules are based on results from one to five PT samples "analyzed" at the same time. Because the effectiveness of the criteria set for acceptable performance in a PT program is influenced by the population SD, each rule's capabilities were examined for PT populations with interlaboratory SDs ranging from 1% through 10% of the population mean value. All rules achieve their maximum efficiency over a narrow range of interlaboratory SDs. For PT evaluations of intralaboratory performance to be optimally effective, selection of the rule must be based on the SD of the PT population.
Extrinsic-pathway enzyme-linked coagulation assay (EP-ELCA). A clot-based alternative to prothrombin time for measurement of extrinsic pathway factors in plasma.
Authors: Doellgast G J , Triscott M X , Buss D H , West J 
Published: January 2020

Abstract
This solid-phase colorimetric microtiter-plate clotting assay is much more sensitive than standard clotting tests. In enzyme-linked coagulation assay (ELCA), enzyme-labeled fibrinogen and solid-phase fibrinogen are the substrate for thrombin generated in the clotting cascade. We used this assay to measure the factors of the extrinsic pathway by an extrinsic pathway-specific assay (EP-ELCA) and to determine the individual factors of the extrinsic pathway (VII, X, V, II) in plasmas of coumadin-treated and heparin-treated patients, with prothrombin time (PT) values used as a reference. In the ELCA method, samples and controls are incubated on the same plate, eliminating the requirement for pre-standardization of the substrate "plasma" before the factor assay is done. Concentrations of factors are determined by serially diluting sample and control plasmas to yield equivalent activity at given dilutions, a more direct approach for measuring specific factors than determining log concentrations vs log clotting time. Changes in the concentrations of clotting factors are seen before changes are apparent by PT. For coumadin-treated patients, all vitamin K-dependent factors were significantly (P less than or equal to 0.001) less than in normal controls, whereas factor V concentrations were normal, as expected. For patients treated with heparin, concentrations of factors X and VII were less than in normal controls (P less than 0.01) and results for EP-ELCA, II, and V assays were normal. This methodology can readily be automated.
Serum fructosamine in diabetic pregnancy.
Authors: Frandsen E K , Sabagh T , Bacchus R A 
Published: January 2020

Abstract
Serum fructosamine was measured in 275 blood donors, in 559 subjects with a normal pregnancy, in 32 gestational diabetics being treated with insulin and 69 being treated by diet only, and in 53 pregnant subjects with established diabetes. In none of the pregnant subgroups did the mean fructosamine concentration exceed that of the donor group. The concentration in normal pregnant subjects showed a modest but significant decrease with gestational age and an increase with maternal age. Hyperglycemic non-pregnant subjects (n = 24) had significantly increased serum fructosamine concentrations, and 96% of these subjects exceeded the upper 95% confidence limit for fructosamine in the donor group. A highly significant correlation was demonstrated between serum fructosamine and preprandial plasma glucose in the hyperglycemic subjects. A weak, but significant, correlation was shown for the entire population sample of antenatal patients, while this was non-significant within each of the sub-groups comprising established diabetics and gestational diabetics, respectively.
Radioenzymatic assay of catecholamines in plasma after a preliminary solvent extraction compared with an analogous liquid-chromatographic method.
Authors: Feoli J , Bijault C , Dehennin L 
Published: January 2020

Abstract
Catechol-borate complexation and ion-pair formation combined with organic solvent extraction as preliminaries to radioenzymatic assay (REA) with catechol-O-methyltransferase-catalyzed methylation allows the quantification of catecholamines in plasma samples of any volume. We attained improved detection limits for 1-mL samples: 9 ng/L for norepinephrine (NE), 8 ng/L for epinephrine (E), and 11 ng/L for dopamine (DA). Precision data resemble those obtained by REA for small-volume samples. Comparison with a liquid chromatography-electrochemical detection (LCEC) technique showed the two methods to be equivalent for NE and E determinations, but DA estimations were lower by REA than by LCEC.