bluuebunny/crossref_metadata_2025_split huggingface dataset:
Validity of analog free thyroxin immunoassays.
Authors: Ekins R 
Published: January 2020

Abstract
I have briefly illustrated the way in which the main features of analog methods may be readily predicted by consideration of elementary physicochemical laws. (Editorial limitations on the length of this presentation have prevented exploration of other issues such as the reasons for, and effects of, the hitherto unexplained inclusion by manufacturers of large amounts of albumin (12, 18) in kit reagents.) The main implication of our analysis is that, to conform genuinely to the principles of "unbound analog" free hormone immunoassay, an analog must bind to serum proteins to a maximal extent of approximately 10% (but preferably less) in the absence of antibody. The notion that an analog is suitable for use in this context merely if it binds to serum proteins with lower affinities than does the native hormone (6) is demonstrably fallacious. Current analog methods thus neither adhere to the principles of unbound analog free hormone assay nor do they survive classic dilution tests of free hormone assay validity. Demonstrably they do not, in a general sense, measure the free hormone in serum. They may nevertheless yield roughly "correct" values in pregnancy (and thus, arguably, possess clinical value) if the analog fortuitously distributes in an optimal manner between serum proteins, implying approximate balance between the biasing effects caused by the protein changes occurring in pregnancy. However, such methods yield incorrect estimates in all other situations in which the binding characteristics of test samples are disturbed (e.g., by the presence of binding competitors, drugs, abnormal proteins, etc. or when "unbalanced" changes in protein concentration occur), this being the fundamental cause of their diagnostic unreliability. Wilkins, Midgley, and their colleagues have consistently opposed these conclusions, although they have never (using their computer model or by other rigorous means) demonstrated them to be incorrect, nor indeed have they ever formally substantiated the physicochemical propositions on which they themselves claim the methodology rests. Furthermore, they have repeatedly misinterpreted experimental results yielded by the Amerlex kits (such as the effects thereon of serum dilution, NEFA, drugs, etc.), discreetly abandoning (and even totally reversing) their original claims (though not withdrawing them) when these appeared no longer tenable. Perhaps the most serious consequence of these events is the resulting confusion in the literature. This is of major importance in physiological research (28), but it also clearly has major implications in clinical chemistry.(ABSTRACT TRUNCATED AT 400 WORDS)
Patterns of porphyrin excretion in feces as determined by liquid chromatography; reference values and the effect of flora suppression.
Authors: Beukeveld G J , Wolthers B G , van Saene J J , de Haan T H , de Ruyter-Buitenhuis L W , van Saene R H 
Published: January 2020

Abstract
While determining reference values for porphyrins in feces as measured by liquid chromatography, we observed strong fluctuations in fecal porphyrin contents. To explain these fluctuations, we selectively suppressed the intestinal flora of healthy persons. Suppression of aerobic flora had no effect on fecal porphyrin excretions, whereas suppression of anaerobic flora completely inhibited the transformation of protoporphyrin to pempto- and deuteroporphyrin for as long as five days after stopping medication. During this latter, the conversion to mesoporphyrin was clearly increased in one person and in others partly affected or decreased. During complete suppression of flora for prolonged periods, the production of proto- and coproporphyrins was decreased and deutero-, pempto-, and mesoporphyrins were absent. We conclude that the nature of fecal porphyrins is mostly affected by action of anaerobic bacteria, different kinds of bacteria having different effects. Some, like aerobic Gram-negative bacteria, have little or no effect on porphyrins; some cause production of mesoporphyrin; some promote a conversion to pempto- and deuteroporphyrin; and some mainly cause production of copro- and protoporphyrin. We give examples in which normal to slightly increased excretions of fecal porphyrin do not exclude a diagnosis of porphyria, and relatively high concentrations do not confirm one.
Liquid-chromatographic measurement of catecholamines and metabolites in plasma and urine.
Authors: Foti A , Kimura S , DeQuattro V , Lee D 
Published: January 2020

Abstract
In this general method for measuring the concentrations of neurotransmitters in body fluids by "high performance" liquid chromatography (HPLC), the procedures for extracting different biogenic amines from body fluids vary, but the basic chromatographic conditions are the same for all. We use citric/formic acid buffer as the mobile phase, a C18 column, and an electrochemical detector. Specificity is better than in previously reported methods. Because of its excellent cost efficiency, we consider this to be the method of choice for quantifying biogenic amines.
Simultaneous determination of trace elements in lavage fluids from human bronchial alveoli by energy-dispersive x-ray fluorescence. 3. Routine analysis.
Authors: Maier E A , Dietemann-Molard A , Rastegar F , Heimburger R , Ruch C , Maier A , Roegel E , Leroy M J 
Published: January 2020

Abstract
We applied the energy-dispersive x-ray fluorescence technique to determination of trace elements in human bronchoalveolar lavage fluids. Our analysis of more than 200 samples allowed us to determine normal reference values, to be used in characterizing occupational exposure. These values are expressed both in nanograms per 1000 cells (of all kinds) and nanograms per 1000 macrophages to correlate lavage efficiency and dust content of the alveoli. The result expressed in milligrams per liter is not sufficient, because some healthy volunteers showed high concentrations of iron but normal values when expressed vs the number of cells. Some examples of abnormal compositions of broncho-alveolar lavages are reported and the fully automated spectrometer developed for clinical and biological investigations is described.
An international collaborative study on standardization of apolipoproteins A-I and B. Part II. Evaluation of contributions of antisera to among-laboratory variance components.
Authors: Henderson L O , Hannon W H , Smith S J , Cooper G R 
Published: January 2020

Abstract
Local antisera (LA) were compared with a common interim reference antiserum (IRA) to examine the antiserum component of the among-laboratory variation in an international collaborative study with 28 laboratories evaluating a candidate international Reference Material (apo-RM) for apolipoproteins A-I (apo A-I) and B (apo B). Measurement of the relative concentration of lyophilized preparations differed by less than 1% for LA and IRA. The percentage of the total variation in measurement of the concentration of apo-RM that was contributed by antisera among laboratories was 5% and 8% for apo A-I and B, respectively. Estimated differences from overall mean concentrations for the five different immuno-methods were greater for apo B (range: +22% to -23.5%) than for apo A-I (range +14% to -14%), but were similar within a method for LA and IRA. The results indicated that antisera are not a major source of error among laboratories and, indeed, are responsible for relatively little of the total variability.
Evaluation of a monoclonal immunoradiometric assay for prostate-specific antigen.
Authors: Rock R C , Chan D W , Bruzek D , Waldron C , Oesterling J , Walsh P 
Published: January 2020

Abstract
We evaluated the analytical performance of a new monoclonal immunoradiometric assay ("M-PSA") for prostate-specific antigen ("Tandem"; Hybritech Inc.) in comparison with a monoclonal immunoradiometric assay ("M-PAP") for mass measurement of prostatic acid phosphatase ("Tandem") and with a conventional enzyme-activity assay ("E-PAP") for prostatic acid phosphatase (EC 3.1.3.2). For M-PSA, the CVs were 1.3-3.0% within-run and 3.0-4.9% between-run. The minimum detectable mass concentration was 0.10 microgram/L, and linearity extended to 100 micrograms/L. The reference interval for M-PSA in 178 healthy men was 0-2.8 micrograms/L. Serum specimens from men with prostatic disease (primarily prostatic carcinoma and benign prostatic hypertrophy) were assayed by the three methods. Correlation was best between mass measurement (M-PAP) and enzyme activity (E-PAP) for prostatic acid phosphatase (r = 0.958). Results for PSA did not correlate well with those for either M-PAP (r = 0.629) or E-PAP (r = 0.387). PSA was increased in a higher percentage of specimens from men with earlier (clinical stage B) prostatic carcinoma than were results from either assay for PAP.
An alternative fluorescence enhancement solution for use in lanthanide-based time-resolved fluoroimmunoassays.
Authors: Keelan J A , France J T , Barling P M 
Published: January 2020

Abstract
Time-resolved fluoroimmunoassays that make use of lanthanide chelates as labels require the addition of an enhancement solution to elicit the formation of a fluorescent lanthanide complex. All solutions previously described are based on 2-naphthoyltrifluoroacetone (NTA), a beta-diketone. Currently, this compound is not commercially available. We report here the properties and performance of an enhancement solution prepared with a commercially available beta-diketone, thenoyltrifluoroacetone. Use of this solution in a commercial time-resolved fluoroimmunoassay gave results essentially identical to those obtained with the NTA-based solution, although fluorescence emission was approximately 27% lower. The lower fluorescence yield did not, however, significantly reduce assay sensitivity. We conclude that this solution represents a viable and highly economical alternative to the preparation currently in use, particularly for laboratories wishing to develop their own assays based on lanthanide fluorescence.
Stability of 5-fluorouracil in whole blood and plasma.
Authors: Murphy R F , Balis F M , Poplack D G 
Published: January 2020

Abstract
We studied the stability of 5-fluorouracil (5-FU) in plasma and whole blood kept at room temperature and on ice for 1 to 24 h. At room temperature, there was a steady loss of 94% of the parent drug over 24 h in whole blood and 52% in plasma. In the presence of an excess of uracil, 5-FU was stable for 24 h, suggesting that the loss of 5-FU is the result of enzymatic degradation. 5-FU is more stable in whole blood and plasma when samples are kept cold. For blood and plasma samples maintained on ice, the loss was only 30% and 10% of the parent drug in the respective samples over 24 h. Frozen plasma samples (-20 degrees C) were stable for five weeks. Blood specimens collected for quantifying 5-FU should be immediately placed on ice, and the plasma should be separated and frozen as promptly as possible.
Accuracy and precision of breath-alcohol measurements for a random subject in the postabsorptive state.
Authors: Simpson G 
Published: January 2020

Abstract
The accuracy of estimates of blood-alcohol concentration based on measurements of breath-alcohol concentration in a randomly selected subject by a random quantitative evidential breath-alcohol analyzer is evaluated with respect to the breath analyzer itself, its calibration, and the biological variables of the subject being tested. There are no suitable experimental data for rigorous determination of the overall accuracy, so I estimate it from the CV of the available data. I find that the uncertainty in these breath-analyzer readings for a random subject in the postabsorptive state is at least +/- 15%, +/- 19%, or +/- 27%, depending on whether +/- 2 CV, the experimental range, or +/- 3 CV, respectively, is used to express the overall uncertainty. Over 90% of this uncertainty is due to biological variables of the subject, and at least 23% of subjects will have their actual blood-alcohol concentration overestimated. Manufacturers' specifications for the accuracy and precision of these instruments are inconsistent with the experimental values reported in the literature and I recommend that an appropriate amount of uncertainty be reflected in the results from these breath analyzers, especially when they are used for law-enforcement purposes.
Assay of serum fructosamine that minimizes standardization and matrix problems: use to assess components of biological variation.
Authors: Howey J E , Browning M C , Fraser C G 
Published: January 2020

Abstract
Methodological problems with the assay of fructosamine in serum--standardization, matrix effects, and dependence on buffer pH--have been minimized with a method involving colorimetric assay of each specimen and subsequent re-assay after standard addition of 1-deoxy-1-morpholinofructose. Absorbance at optimum wavelength of 540 nm varies linearly with fructosamine concentration to at least 5.5 mmol/L, and between-run precision is about 6% for both patients' specimens and quality control materials. Correction of fructosamine to serum albumin of 40 g/L minimizes the effect of albumin while maintaining transferability of data and reference values. From data on biological variation, the analytical goal for precision (CV) is less than or equal to 2.6%. The square root of the ratio of intra- to interindividual variance is low, indicating that fructosamine concentrations have a high index of individuality; thus conventional population-based reference values are of limited use. Although this assay may be useful in monitoring disease, we doubt that it provides a valid screening test for diabetes.
Kinetic study of the Jaffé reaction for quantifying creatinine in serum: 1. Alkalinity controlled with NaOH.
Authors: Pardue H L , Bacon B L , Nevius M G , Skoug J W 
Published: January 2020

Abstract
We studied the kinetic behavior of the reaction of alkaline picrate and creatinine and evaluated a nonlinear curve-fitting method for quantifying creatinine in serum. Using a 3 X 3 factorial experimental design, we evaluated interactive effects among temperature and concentrations of creatinine, picrate, and NaOH. We found no evidence of interference by glucose or unconjugated bilirubin; the effects of the acetoacetate reaction, which is fast, are easily compensated by the curve-fitting method. The reaction with human serum albumin is very complex, but its effects are compensated by the curve-fitting method and by preparing standards containing 50 g of albumin per liter. Calibration plots are linear under a wide variety of conditions for both aqueous standards and standard additions of creatinine to pooled serum. Reproducibility studies with standards containing creatinine at 2, 10, and 20 mg/L yielded relative standard deviations (RSD) of 8.2, 2.5, and 1.3%, corresponding to absolute variations of 0.16, 0.25, and 0.26 mg/L. The average SD for 17 sera containing creatinine at 15-50 mg/L was 0.7 mg/L. The averages of ratios (as percent) of determined vs expected concentrations in 17 sera with added creatinine (7.27 mg/L) were 97.8% for aqueous standards, 99.9% for standards with added albumin.
Proteinuria in health and disease assessed by measuring the urinary protein/creatinine ratio.
Authors: Lemann J , Doumas B T 
Published: January 2020

Abstract
We measured daily excretion rates for urinary protein and the ratios of urinary protein to creatinine in 24-h urines and in untimed urines in 60 healthy adults, 30 patients with kidney disease, and 22 kidney-transplant recipients. The ratios for urinary protein/creatinine, mg/g, in untimed urines and in 24-h urines from the same subjects were closely correlated (r = 0.97) for rates of protein excretion ranging from normal (mean 44 mg/day) to nephrotic (maximum 19,300 mg/day). Because urinary protein/creatinine in healthy subjects never exceeded 100 mg/g, we propose that a ratio of less than 100 mg/g in untimed urines, obtained in the absence of exercise, fever, or other evidence of urinary tract disease, is a criterion of normal kidney function. Among patients with nephrotic syndrome (urinary protein excretion rate greater than or equal to 4000 mg/day), urinary protein/creatinine ratios always exceeded 2000 mg/g in both 24-h and untimed urines. Intermediate urinary protein/creatinine ratios (100 to 2000 mg/g) may reflect any type of kidney disease.
Desirable standards of performance for therapeutic drug monitoring.
Authors: Fraser C G 
Published: January 2020

Abstract
Therapeutic drug monitoring is an important aspect of clinical chemistry for which no objective analytical goals yet exist. Based on fundamental pharmacokinetic theory, and the current consensus strategy for analytical goal-setting for precision based upon biological variation, a theoretical model allows derivation of the goal that: analytical CV less than or equal to 1/4 [(2T/t - 1)/(2T/t + 1)] X 100%, where T is the time interval between doses, and t is the average elimination half-life. Using published data on half-lives, I have derived goals for analysis for (e.g.) digoxin, lithium, some antiepileptic drugs, and theophylline. The goal for accuracy proposed is that methods should have no bias and should generate true values. Goals for precision should therefore be viewed as goals for total analytical error.
Gas chromatographic-mass spectrometric assay for 6-hydroxymelatonin sulfate and 6-hydroxymelatonin glucuronide in urine.
Authors: Francis P L , Leone A M , Young I M , Stovell P , Silman R E 
Published: January 2020

Abstract
Circulating melatonin is hydroxylated to 6-hydroxymelatonin and excreted in urine as the sulfate and glucuronide conjugates. We extracted these two compounds from urine by using octadecylsilane-bonded silica cartridges to eliminate most of the urea and electrolytes, and silica cartridges to separate the sulfate and glucuronide conjugates. After hydrolyzing the separated conjugates enzymically, we determined the free hydroxymelatonin by gas chromatography-mass spectrometry. Though recoveries were low and variable, we were able to quantify the analyte in the original sample by adding deuterated sulfate and glucuronide conjugates to the urines before extraction.
Metabolic profiles of urinary organic acids recovered from absorbent filter paper.
Authors: Chamberlin B A , Sweeley C C 
Published: January 2020

Abstract
We evaluated for reliability and reproducibility a semiquantitative gas-chromatographic assay of organic acids in samples of normal urine recovered from absorbent filter paper. We also evaluated this method for use in diagnosis of some of the more common organic acidurias. Transfer of urine from diapers to absorbent filter paper eases the usual trauma of specimen collection from young children; it also simplifies sample storage and shipment.
Lactate and pyruvate electrochemical biosensors for whole blood in extracorporeal experiments with an endocrine artificial pancreas.
Authors: Mascini M , Mazzei F , Moscone D , Calabrese G , Benedetti M M 
Published: January 2020

Abstract
Glucose, lactate, and pyruvate can be continuously measured in whole blood by using three extracorporeal electrochemical biosensors. We fixed two newly developed sensors, for lactate and pyruvate, in series with an endocrine artificial pancreas ("Betalike") without affecting its performance. These new sensors for use with whole blood should be able to clarify the fate of the intermediary metabolites of glucose in diabetic patients receiving infusions of drugs or insulin.
Digoxin-like immunoreactivity eliminated from serum by centrifugal ultrafiltration before fluorescence polarization immunoassay of digoxin.
Authors: Christenson R H , Studenberg S D , Beck-Davis S , Sedor F A 
Published: January 2020

Abstract
Digoxin determined in the Abbott "TDx" by fluorescence polarization immunoassay by the manufacturer's recommended method involving precipitation of protein with 5-sulfosalicylic acid (SSA) is subject to interference from endogenous compounds having digoxin-like immunoreactivity. Guided by the work of Graves et al. (Clin Chem 1986;32:1506-9), we eliminated interference caused by digoxin-like immunoreactivity by substituting ultrafiltration for precipitation with SSA to remove protein. Using the manufacturer's method, we quantified digoxin in serum from 53 patients in three clinically defined groups who were receiving no digoxin, finding apparent digoxin in excess of the 200 ng/L detection limit in 24% of the 17 pregnant women, 59% of the 17 renal-dialysis patients, and all of 19 neonatal cord-blood samples examined. No measurable digoxin immunoreactivity was observed by fluorescence polarization immunoassay for any of the 53 clinically defined patients after removal of protein by ultrafiltration. For 22 men for whom digoxin was prescribed, digoxin measurement after protein removal by SSA and by ultrafiltration correlated well (r = 0.98), with good proportionality (slope = 1.04). Analytical recovery of added digoxin from adulterated serum was 115% after SSA, but 100% after ultrafiltration. Thus, before this assay procedure, we recommend ultrafiltration, to remove digoxin-like interference.
Enzyme-linked immunosorbent assay for urinary albumin at low concentrations.
Authors: Krämer B K , Jesse U , Ress K M , Schmülling R M , Risler T 
Published: January 2020

Abstract
We describe an enzyme-linked immunosorbent assay (ELISA) for urinary albumin. It requires only commercially available reagents, can detect as little as 16 micrograms of albumin per liter, and analytical recovery ranges from 92 to 116%. The assay is simple, rapid, and inexpensive. Albumin excretion was 6.2 (SD 4.1) mg/24 h in healthy subjects (n = 40), 14.7 (SD 7.2) mg/24 h in albumin-test-strip-negative Type I diabetics (n = 11), and 19.7 (SD 16.2) mg/24 h in patients with essential hypertension (n = 12).
Oxybuprocaine and five metabolites simultaneously determined in urine by gas chromatography and gas chromatography-mass spectrometry after extraction with Extrelut.
Authors: Kasuya F , Igarashi K , Fukui M 
Published: January 2020

Abstract
We describe a gas-liquid chromatographic (GC) method for determination of oxybuprocaine, and a gas chromatographic-mass spectrometric (GC-MS) method for simultaneous determination of four of its nine metabolites in urine. We used an Extrelut column to simply and rapidly extract oxybuprocaine and its metabolites from urine. For the GC-MS analyses, we monitored the characteristic fragment ions at m/z 353, 395, 369, 411, and 235 for 3-butoxy-4-aminobenzoic acid (metabolite 2, M-2), 3-butoxy-4-acetylaminobenzoic acid (M-3), 3-hydroxy-4-aminobenzoic acid (M-4), 3-hydroxy-4-acetylaminobenzoic acid (M-5), and methaqualone (internal standard), respectively. We quantified the glucuronide of M-2 after enzymic treatment. The assay's selectivity and reproducibility (within-day and between-day CVs less than 8% for all metabolites) make it applicable to determine oxybuprocaine and its metabolites in human urine. Mean 9-h urinary excretion of oxybuprocaine and its five metabolites from four healthy volunteers was 89.2% after a 100-mg oral dose.