bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas-chromatographic determination of ethanol in blood with 0.53-mm fused-silica open tubular columns.
Authors: Penton Z
Published: January 2020

Several 0.53 mm (i.d.) fused-silica open tubular columns were evaluated for the gas-chromatographic determination of ethanol and other volatiles in blood by both headspace and liquid injection. These columns offer the advantages of fused-silica technology without requiring expensive modification of the instrument for capillary. Methyl silicone columns of various lengths and film thicknesses were examined and also a polyethylene glycol column. The merits of each column are discussed and relative retention times are given.
Routine urinalysis (dipstick) findings in mass screening of healthy adults.
Authors: Carel R S , Silverberg D S , Kaminsky R , Aviram A
Published: January 2020

We present results of simple urinalysis examinations (dipstick) in a large (approximately 21,000 people) working population. In about 10% of the screened individuals at least one abnormality was found. In men the most common finding was proteinuria (4.9%). Hematuria was found in 2.6% and glycosuria in 0.6%. The most prevalent finding in women was hematuria (8.1%), followed by proteinuria (3.9%) and glycosuria (0.6%). Only about 1% of the examinees had two or more abnormalities in their urine examinations. These findings attest to the utility and practicability of incorporating urine testing into various screening and clinical examinations.
Interference of the chemotherapeutic agent etoposide with the direct phosphotungstic acid method for uric acid.
Authors: Matheke M L , Kessler G , Chan K M
Published: January 2020

A 62-year-old woman receiving chemotherapy with etoposide showed discrepant uric acid values as measured by a direct phosphotungstic acid (PTA) method (150 mg/L) compared with a uricase technique (40 mg/L). After ultrafiltration, the positive interference for the direct PTA method was retained in the protein fraction, but not in the filtrate. Adding exogenous etoposide to drug-free serum confirmed this interference for the direct PTA method, but not for the uricase procedure or a PTA technique preceded by dialysis. Decisions for aggressive patient management are often based on the magnitude of hyperuricemia. We do not recommend that the direct phosphotungstic acid method be used to measure uric acid in patients receiving etoposide.
Validity of analog free thyroxin immunoassays.
Authors: Ekins R
Published: January 2020

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Accuracy and precision of breath alcohol measurements for subjects in the absorptive state.
Authors: Simpson G
Published: January 2020

Published data are analyzed in order to estimate the accuracy of breath-alcohol measurements for subjects during absorption of orally ingested ethanol. Simultaneous measurements of breath alcohol concentration (BrAC) and venous blood alcohol concentration (VBAC) show that actual VBAC can be overestimated by more than 100% for a significant amount of time after drinking stops. The maximum error found for four individual subjects is +230%, +190%, +60%, and +30%. The magnitude of these errors indicates that results from quantitative evidential breath alcohol analyzers are far less accurate for the absorptive state than they are during the postabsorptive state, but the specifications for accuracy and precision given by manufacturers of these instruments do not reflect this. The results also indicate that there is a significant likelihood that subjects will be in the absorptive state when tested under field conditions. I conclude that estimates of BAC based on BrAC measurements are not reliable in the absorptive state and that the uncertainty associated with such estimates should be accounted for, particularly when the results are used in connection with law enforcement.
Fluorometric determination of indocyanine green in plasma.
Authors: Hollins B , Noe B , Henderson J M
Published: January 2020

With this fluorometric method for measuring indocyanine green (ICG) in biological fluids, the limit of detection is an order of magnitude lower than for the traditional spectrophotometric procedure. The excitation and emission maxima are 780 and 810 nm, respectively. Agreement was excellent (r = 0.998) between direct results by this method and those by a liquid-chromatographic procedure with spectrophotometric detection. ICG breaks down in aqueous solution; the degradation products can be detected with liquid-chromatographic/spectrophotometric methods, but because the metabolites are not fluorescent, they do not interfere in the method present here. The increased specificity and sensitivity of this method should permit much more complete analysis of the kinetics of ICG disposition.
Assessment of urinary retinol-binding protein as an index of proximal tubular injury.
Authors: Bernard A M , Vyskocil A A , Mahieu P , Lauwerys R R
Published: January 2020

The urinary excretion of retinol-binding protein (RBP), beta 2-microglobulin (beta 2-m), and beta-N-acetyl-D-glucosaminidase was monitored in patients with renal tubular damage secondary to multiple injuries, rhabdomyolysis, antibiotic treatment, or poisoning by various chemicals such as solvents, heavy metals, or pesticides. In almost all cases, RBP proved to be a more sensitive index of renal tubular damage than was beta-N-acetyl-D-glucosaminidase and, being more stable in acid urine, a more practical analyte to measure than was beta 2-m. We corroborated this finding by studying the relationships between these three analytes in more than 150 patients. On the average, an increase in the urinary excretion of beta-N-acetyl-D-glucosaminidase becomes detectable when urinary RBP already exceeds the normal value by 50- to 100-fold. In urines with pH greater than 6, RBP and beta 2-m concentrations are well correlated (r = 0.93, n = 150), beta 2-m tending to be more frequently positive (i.e., greater than 311 micrograms/L). But in urines with pH less than 6 (about 30-40% of the samples), the RBP/beta 2-m concentration ratio increases as pH decreases, up to 500 in some patients with massive tubular injury. Because the renal uptake of proteins involves a saturable process, the urinary excretion of RBP, like that of beta 2-m, specifically reflects the reabsorption capacity of proximal tubules only when the glomerular filtration rate is normal or slightly impaired (i.e., serum creatinine less than 20 mg/L). Under these conditions the determination of RBP protein in urine appears the most appropriate test when early detection of tubular injury is desirable.
Interlaboratory proficiency-testing programs: a computer model to assess their capability to correctly characterize intralaboratory performance.
Authors: Ehrmeyer S S , Laessig R H
Published: January 2020

We developed a computer model of an interlaboratory survey program to study the ability of proficiency testing (PT) programs to detect intralaboratory errors (total, random, and systematic). It uses a base interlaboratory PT population of 400 laboratories and one test laboratory each with uniquely defined intralaboratory characteristics, i.e., mean, standard deviation (SD), and bias. A gaussian random-number generator uses these parameters to simulate 401 test results analogous to the analysis of one PT sample by each laboratory. The test laboratory's intralaboratory error is expressed as various combinations of bias and coefficient of variation (CV); its simulated survey result is evaluated by a performance criterion derived from the group statistics. To eliminate statistical artifacts, the computer model repeats the complete simulation process 400 times and determines the percentage of the test laboratory's results that fail to meet a specified performance criterion. The computer model can use assigned values or actual intralaboratory data.
Improved method for quantifying vitamin D in proprietary infants' formulas and in breast milk.
Authors: Ballester I , Cortes E , Moya M , Campello M J
Published: January 2020

In this new method for quantifying vitamin D in infants' formulas and breast milk, after repeated lipid extraction, samples are further purified by passage through Sep-Pak cartridges, followed by liquid chromatography, then quantified by competitive protein-binding assay. Analytical recovery is estimated by use of added 3H-labeled vitamin D. For repeated assays of a reconstituted proprietary powdered milk formula in two runs, the intra-assay vitamin D values were 9.0 (SD 1.4) (n = 6) and 8.9 (SD 1.6) micrograms/L (n = 7) (t = 0.07). Assay of a proprietary liquid formula yielded values of 14.9 (SD 0.9) micrograms/L (n = 6). For each, the results agreed with the vitamin D content shown on the label. Vitamin D concentrations in breast milk from two groups of lactating mothers of different social class and nutritional status were 2.3 (SD 1.4) (n = 7) and 2.0 (SD 1.7) micrograms/L (n = 7). Overall recoveries ranged from 65 to 75%. Only 2 mL of milk is required, which facilitates sample collection, and the assay is less time-consuming than other current methods.
Reassessment of creatine kinase BB as a marker for cancer of the prostate, breast, and lung.
Authors: Wong S S , Wu A H , Fritsche H A
Published: January 2020

We used an enzyme-linked immunoabsorbent assay to measure creatine kinase (CK; EC 2.7.3.2) BB in the sera of 58 cancer patients. A pre-incubation step with an anti-CK-M antibody-coated bead removed M chain components, and CK-BB was quantified with use of an anti-CK-B antibody-coated tube. No cross reactivity was observed with mitochondrial CK or CK-MM; CK-MB cross reacted slightly (1.6%). Macro CK type 1 was measured as CK-BB. Average analytical recovery of purified CK-BB added to serum was 97.7%. Although the enzyme activity of CK-BB is labile, our studies show that this protein is antigenically stable for 12 months when stored frozen. The upper limit of normal for CK-BB concentration was 0.3 micrograms/L (95th percentile, n = 25). Of the 20 cases of breast cancer of various stages, none showed any increases of serum CK-BB. Only two of 18 patients with prostatic carcinoma (stage D), and two of 10 patients with oat-cell carcinoma of the lung had increased concentrations of CK-BB in the serum. Ten patients with squamous cell cancer of the lung had normal concentration of the enzyme. Thus the CK-BB isoenzyme is not frequently increased in cancers of the prostate, lung, and breast, and it has little apparent value as a tumor marker for these diseases.
Another physician's office analyzer: the Abbott "Vision" evaluated.
Authors: Hicks J M , Iosefsohn M
Published: January 2020

We evaluated the Abbott Vision system, to assess its suitability for use in the physician's office setting. We compared results from Vision for all the available analytes (alkaline phosphatase, urea nitrogen, cholesterol, creatinine, glucose, uric acid, and triglycerides) with results from the Kodak Ektachem 400 and 700. For all analytes, standard curve linearity, assessed with various dilutions of an analyte-supplemented serum pool, was within the ranges claimed by the manufacturer. Within-run precision (CV) for assays of these analytes ranged from 0.9% to 4.7%, run-to-run precision from 1.1% to 7.3%. Comparisons with other methods were generally very good except for a bias in results for blood urea nitrogen and alkaline phosphatase. Hemolysis (hemoglobin at 2.0 and 3.0 g/L) interferes with results for cholesterol, glucose, triglycerides, and uric acid in serum and whole blood. Bilirubin at 82 mg/L interferes with results for creatinine and triglycerides; at 120 mg/L it interferes with cholesterol, glucose, and uric acid results; and at 170 mg/L it interferes with alkaline phosphatase results. Triglycerides up to 5000 mg/L do not interfere with any of the tests. Calibration of the analyzer was stable for one month. We also compared the performance of a skilled operator with that of an unskilled operator and a physician.
Bromcresol purple dye-binding methods underestimate albumin that is carrying covalently bound bilirubin.
Authors: Bush V , Reed R G
Published: January 2020

We used automated and manual versions of two commonly used dye-binding methods for albumin to quantify albumin that had been modified by covalent addition of bilirubin. Dye-binding methods based on reaction with bromcresol purple underestimated the modified albumin by as much as 29%. Dye-binding methods based on reaction with bromcresol green were unaffected by the presence of covalently attached bilirubin. Neither method was affected by the presence of noncovalently bound bilirubin.
Automated analysis for taurine in biological fluids and tissues.
Authors: Goodman H O , Shihabi Z K
Published: January 2020

We have developed an automated method of analysis for taurine, based on incorporating an ion-exchange chromatography column into the continuous-flow AutoAnalyzer (Technicon). After removal of proteins and peptides by dialysis, taurine is selectively eluted from an ion-exchange column and reacted with o-phthaldialdehyde to yield a fluorescent compound. The advantages of this method are: full automation with no need for sample deproteinization or cleanup; sensitivity, detecting as little as 5 mumol/L; speed (20 samples per hour); and flexibility. It can be used for assaying taurine in urine, plasma, cerebrospinal fluid, and tissue homogenates. This method can be adapted for assays of other metabolites.
Biological variation in analyte concentrations in urine of apparently healthy men and women.
Authors: Gowans E M , Fraser C G
Published: January 2020

Analytical, intra-individual, and interindividual components of variation for sodium, potassium, urea, creatinine, calcium, and phosphate were estimated from results for 24-h urine specimens collected from 15 apparently healthy individuals every four weeks for 40 weeks. Expressed as output, mean values differed for men and women, except for calcium. Our data on intra-individual variation were similar to those obtained for 10 men by Shephard et al. (Clin Chem 1981;27:569-73). Calculated analytical goals are easily attained by current methods. Reference values for urine creatinine are useful only when expressed as output and stratified according to gender. The ratios of intra- to interindividual variation generally increase on such stratification; separate reference values for men and women are therefore required for analytes expressed as output. Measurements of sodium and potassium in urine should be reported as concentration, but output terms are favored for the other analytes. Differences for two serial results from an individual must be rather large to differ statistically.
Storage conditions and stability of thyrotropin and thyroid hormones on filter paper.
Authors: Waite K V , Maberly G F , Eastman C J
Published: January 2020

We evaluated the effects of temperature and humidity on thyroid hormones (T4, T3) and thyrotropin (TSH) measured in blood spots dried on filter paper. RIAs for T4 and T3 blood spots were optimized to measure these analytes over the neonatal and euthyroid adult reference intervals. Sensitivities of the T3 and T4 assays were 0.5 and 10 nmol/L, respectively. A blood-spot immunoradiometric assay for TSH involving magnetizable particles was developed with a sensitivity of 6 milli-int. units/L. Control sera stored at -20 degrees C, 4 degrees C, room temperature, 37 degrees C, and at external ambient temperatures for 36 days showed no significant change in measured concentrations of TSH or T3 during 30 days or for T4 at -20 and 4 degrees C. T4 markedly declined in blood spots stored at room temperature (either high or low humidity), 37 degrees C, or ambient temperature. TSH and T3 in blood spots evidently are stable at temperatures likely to be encountered during storage or transport, but blood spots for T4 assay must be stored between -20 and 4 degrees C.
Two-carbon oxalogenesis compared in recurrent calcium oxalate stone formers and normal subjects.
Authors: McWhinney B C , Nagel S L , Cowley D M , Brown J M , Chalmers A H
Published: January 2020

We used a xylitol load to test the two-carbon pathway to oxalate production in humans. Use of this pentose sugar caused a fourfold increase in glycolate excretion, indicating its suitability as a dynamic function test of two-carbon metabolism. However, despite this increase in glycolate excretion in 10 recurrent stone formers and six normal subjects, there was no concomitant increase in oxalate excretion in either group. By comparison, a sucrose load produced no increase in excretion of either glycolate or oxalate. In addition, when we studied four recurrent calcium stone formers on successive diets with various fat content, we found no correlation between high fat intake and increased glycolate or oxalate excretion. In summary, there was no evidence of abnormal fluxes through the two-carbon pathway to oxalate in recurrent stone formers, nor of hyperoxaluria as related to increased intake of sucrose or fat.
Time-resolved immunofluorometric assay of 34-kDa somatomedin-binding protein.
Authors: Koistinen R , Stenman U H , Alfthan H , Seppälä M
Published: January 2020

In this time-resolved immunofluorometric assay for the 34-kDa somatomedin-binding protein (SmBP), affinity-purified polyclonal antibodies are used, along with solid-phase separation of bound and free analyte. The first antibody is bound to polystyrene microtiter wells; the second is labeled with europium(III) chelate. The detection limit of the method is 0.25 microgram/L, much lower than that (about 8 micrograms/L) for radioimmunoassay. By immunofluorometric assay, SmBP is detectable, and could be accurately quantified, in the serum of all 88 individuals we tested, whereas by radioimmunoassay a third of the samples had concentrations below the detection limit. When SmBP was detectable by both methods, the concentrations measured by the two techniques correlated well (r = 0.98).
Using the coefficient of correlation in method-comparison studies.
Authors: Bookbinder M J , Panosian K J
Published: January 2020

The coefficient of correlation (R) is one of the most commonly computed statistics in method-comparison studies. Usually, it is simply quoted without interpretation. In this paper, we show how R may be used to detect interference, nonlinearity, and misuse of the imprecision components. Specifically, one may precisely predict what R should be by considering the imprecisions of the two methods being compared, even before the comparison is performed. When the actual R disagrees with the predicted R, then one of the mentioned effects is present. We also describe a statistical test to detect these effects at the P = 0.05 level, then evaluate this test by using computer simulation and present two examples of its use. We also present the theory underlying the usage of R, including how R is affected by the distribution and range of the data, by the joint imprecisions of the methods being compared, by the sample size, and by the randomness of the specimen-selection process.
Decrease of free thyroxin in serum of lactating women.
Authors: Iwatani Y , Amino N , Tanizawa O , Mori H , Kawashima M , Yabu Y , Miyai K
Published: January 2020

We measured thyroid hormones and thyroxin-binding proteins in serum from 62 normal lactating and 52 nonlactating women at three months postpartum, and compared these values with those for 42 nonpregnant control women of similar age. Mean thyroxin concentrations in the lactating and nonlactating women were significantly (P less than 0.001) lower than that of the nonpregnant controls, but there was no significant difference (P greater than 0.2) in triiodothyronine concentration among these three groups. Free T4 concentration was significantly (P less than 0.01) lower in lactating women than in controls. The reverse-T3 concentrations in both lactating and nonlactating women were significantly (P less than 0.001) lower than in controls, and were significantly (P less than 0.001) lower in lactating than in nonlactating women. The concentration of thyroxin-binding globulin was significantly higher in lactating women than in controls, and the albumin concentration was significantly lower in women postpartum than in controls. Evidently, regulation of thyroid hormone in women postpartum, especially during lactation, differs from that in nonpregnant women.
Differential assay of salivary and pancreatic alpha-amylase in serum and urine, with use of monoclonal antibody to human salivary amylase immobilized on bacterial cell wall.
Authors: Hiroishi S , Matsuyama S , Kurooka S , Sunahara N , Inoue S , Ida T
Published: January 2020

We previously reported (Clin Chim Acta 1986;159:89) that bacterial cell wall chemically coated with a monoclonal antibody specific to human salivary (S) amylase (EC 3.2.1.1) could be successfully used to separate S and pancreatic (P) amylase in solution. We have now applied this method to serum and urine samples and found that the activities of S and P amylases so measured correlated well with those measured by the isoamylase inhibitor method. The present method is simple and reliable for routine clinical tests.
A linear method for determining specific activity of tracers in radioimmunoassays.
Authors: Chiang C S
Published: January 2020

I describe a rapid and objective method for graphically determining specific activity of radioactive tracers by self-displacement. Two sets of results are plotted on the same graph: total/bound counts vs concentration of unlabeled analyte (for the standard curve results) or quantity of radioactivity (for tracer self-displacement results). Because these plots are linear, not only are the difficulties of curve fitting and the need for numerous data points avoided, but also how well the data fit the lines can be assessed by calculating the standard deviation of the slope of the lines. This method minimizes uncertainty between data points, allows easier interpolation, and often yields more precise results than do previously published procedures.
Measurement of direct bilirubin by use of bilirubin oxidase.
Authors: Doumas B T , Perry B , Jendrzejczak B , Davis L
Published: January 2020

We developed an enzymatic method for measuring direct-reacting bilirubin (DBIL) in serum. At pH 4.5, bilirubin oxidase (BOX) oxidizes mono-conjugated bilirubin, di-conjugated bilirubin, and most of the delta-bilirubin to biliverdin. The resulting decrease in absorbance at 460 nm is linearly related to the concentration of DBIL in serum. Mean DBIL values in the 51 patients' sera examined by the BOX method and a diazo procedure (Clin Chem 1982;28:2305) were 45.4 and 42.8 mg/L, respectively. For the same samples, mean values for DBIL and conjugated bilirubin by the Kodak "Ektachem" methods were 50.2 and 24.8 mg/L, respectively. Hemoglobin, up to 1.5 g/L, does not interfere. Unconjugated bilirubin reacts negligibly. Day-to-day CVs were 2.2% and 2.4% at DBIL concentrations of 37 and 74 mg/L, respectively.
Total testosterone, free-androgen index, calculated free testosterone, and free testosterone by analog RIA compared in hirsute women and in otherwise-normal women with altered binding of sex-hormone-binding globulin.
Authors: Wilke T J , Utley D J
Published: January 2020

We compared the clinical value of information on free testosterone as measured with the Coat-A-Count (Diagnostic Products Corp.) radioimmunoassay kit involving a ligand analog with that of total testosterone, the free-androgen index, and free testosterone calculated from concentrations of testosterone, sex-hormone-binding globulin, and albumin, in hirsute women, pregnant women, oral-contraceptive users, women with thyroid disease, and epileptic women taking phenytoin. Total testosterone, the free-androgen index, calculated free testosterone, and free testosterone by RIA were increased in 41-68% of hirsute women. Values for free testosterone increased in the first and third trimesters of pregnancy but remained within normal limits in all non-hirsute groups. Total testosterone was increased in patients having increased sex-hormone-binding globulin, whereas the free-androgen index and, to a lesser extent, calculated free testosterone were significantly decreased. Free testosterone measured by analog RIA not only has greater diagnostic efficiency than total testosterone, it also is technically simpler to determine than the free-androgen index and calculated free testosterone.
Lactate dehydrogenase isoenzymes in serum during recent acute myocardial infarction.
Authors: Rotenberg Z , Weinberger I , Sagie A , Fuchs J , Sperling O , Agmon J
Published: January 2020

Lactate dehydrogenase (LD, EC 1.1.1.27) isoenzymes 1 and 2 and the LD 1:2 ratio were determined in 62 patients with recent myocardial infarction 24, 48, and 72 h after total serum LD activity had returned to normal values. From the results we could define two groups of patients. The first, 40 patients in whom proportions of LD-1 and LD-2 isoenzymes in serum and the LD 1:2 ratio were all within the normal reference interval, all had an uncomplicated course of recovery from myocardial infarction. In the remaining 22 patients, LD-1 still exceeded LD-2 24 to 72 h after total LD activity returned to normal values; i.e., the ratio was similar to that in patients with myocardial infarction. Seven of these 22 patients (32%) had a complicated course, with re-infarction in all seven. Thus, even in the presence of normal total LD activity, a high LD 1:2 ratio may reflect a consistent focal myocardial necrosis in some patients with recent myocardial infarction and may serve as an early marker for further re-infarction.