bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved method for measurement of inorganic phosphate in serum with a centrifugal analyzer.
Authors: Wentz P W , Savory J , Cross R E
Published: January 2020

A direct mehtod [Clin. Chim. Acta 46, 113 (1973)] for determination of inorganic phosphate in serum was adapted for use with a centrifugal analyzer. Contamination is minimized and analysis rate maximized by doing the reaction in the reagent wells of the transfer disc and by utilizing the high-speed spectrophotometric and data-reduction capabilities of the centrifugal analyzer. Hemolysis, icterus, and moderate lipemia cause no interference. Grossly lipemic sera and sera from patients with plasma cell dyscrasias can be analyzed by incorporating appropriate blanking and dilution techniques. The method exhibits excellent sensitivity and precision and results correlate well with those from a continuous-flow procedure.
Direct determination of serum chloride with a semiautomated discrete analyzer.
Authors: Levinson S S
Published: January 2020

I show how mercuric thiocyanate reagent can be used in assaying serum chloride economically, rapidly, and precisely. I used a semiautomated discrete analyzer with direct concentration read-out capability but the method can easily be applied to many mechanized instruments. Linearity between concentration and color is obtained by adding appropriate amounts of mercuric nitrate to the reagent. As many as 300 samples can be assayed per hour, and the method is excellent for emergency use.
Comparison of results for 13 clinical laboratory determinations with three automated analytical systems.
Authors: Sampson E J , Derck D D , Demers L M
Published: January 2020

We evaluated the Abbott Bichromatic Analyzer-100 (ABA-100) for use in the routine clinical chemistry laboratory by examining 13 different determinations that can be performed on the instrument. Results with the Du Pont "aca" and Technicon continuous-flow systems were compared to the ABA-100 in terms of upper limits of linearity, inter-run coefficient of variation, and results for samples from patients. The upper limits of linearity for the methods on the ABA-100 exceeded all of those for the continuous-flow systems, except for urea nitrogen. Precision of the ABA-100 was as good as or better than that of the aca for all determinations, except for glucose in a normal control serum and creatine kinase and creatinine in an above-normal control serum.
Statistical characterization of the random errors in the radioimmunoassay dose--response variable.
Authors: Rodbard D , Lenox R H , Wray H L , Ramseth D
Published: January 2020

We have developed practical methods for evaluating the magnitude of the random errors in radioimmunoassay dose--response variables, and the relationship between this error and position on the dose--response curve. This is important: to obtain appropriate weights for each point on the dose--response curve when utilizing least-squares curve-fitting methods; to evaluate whether the standards and the unknowns are subject to error of the same magnitude; for quality-control purposes; and to study the sources of errors in radioimmunoassay. Both standards and unknowns in radioimmunoassays for cAMP and cGMP were analyzed in triplicate. The same mean (Y), sample standard deviation, sy, and variance (2-y) of the response variable were calculated for each dose level. The relationship between s 2-y and y was calculated utilizing several models. Results for standards and unknowns from several assays were pooled, and a curve smoothing procedure was used to minimize random sampling errors. This pooling increased the reliability of the analysis, and confirmed the presence of the theoretically predicted nonuniformity of variance. Thus, the calculation of results from these radioimmunoassays should utilize a weighted least-squares curve-fitting program. These analyses have been computerized, and can be used as a "pre-processor" for programs for routine analysis of results of radioimmunoassay.
Evaluation of contemporary methods for serum CO2.
Authors: Lustgarten J A , Creno R J , Byrd C G , Wenk R E
Published: January 2020

We evaluated and inter-compared several newer methods for CO2 analysis--titrimetric (Van Slyke), automatic titrator, continuous-flow/indicator, and coupled-enzyme procedures--with respect to accuracy, precision, specificity interferences, and management criteria. All methods studied appeared to be clinically acceptable; but precision decreased (standard deviations increased) for the last two methods in above-normal ranges.
Improved method for measuring fibrinogen in plasma, with use of a plasmin inhibitor.
Authors: Steffen L W , Steffen B W
Published: January 2020

We describe a modified procedure for quantitating plasma fibrinogen by use of the thrombin-clottable protein technique. The method is accurate and requires a0out 30 min to complete. During its formation and isolation, the clot is protected from the degradative action of plasmin by an inhibitor, epsilon-aminocaproic acid.
Fluorometry of plasma amino nitrogen, with use of fluorescamine.
Authors: Klein B , Standaert F
Published: January 2020

We describe a fluorometric procedure, with use of fluorescamine, for determining plasma amino nitrogen in a 10-mul sample of deproteinized plasma. Values for apparently healthy human subjects agree well with those obtained by spectrophotometry. The simplicity and speed of the assay recommends it as a screening procedure for detecting aminoacidopathies.
High-pressure liquid-chromatographic separation of lactate dehydrogenase isoenzymes.
Authors: Kudirka P J , Schroeder R R , Hewitt T E , Toren E C
Published: January 2020

The isoenzymes of lactate dehydrogenase (EC 1.1.1.27) were separated with excellent resolution in less than 1 h by high-pressure anion-exchange chromatography. These isoenzymes were determined in some tissue extracts and high-activity serum samples by this technique.
Performance studies on the Technicon "SMAC" analyzer: Precision and comparison of values with methods in routine laboratory service.
Authors: Westgard J O , Carey R N , Feldbruegge D H , Jenkins L M
Published: January 2020

We present performance studies on the Technicon "SMAC" analyzer. Precision was estimated from control data during routine operation and from blind duplicates of sera from patients. Patients' specimens were analyzed with the SMAC and the SMA 12/60 during initial evaluation studies. Comparisons were also made with the Du Pont aca and other methods during routine service. Performance is judged relative to medical usefulness requirements, by using previously developed criteria and recommendations for decision levels and allowable errors.
Serum iron determination in patients receiving therapy with iron dextran ("Imferon").
Authors: McIntosh M E , Lynn J K , Meyerriecks N , Contant I
Published: January 2020

Imferon (Lakeside Labs., Inc.), an iron dextran complex, is widely used for parenteral therapy with iron. Colorimetry and atomic absorption spectroscopy give different values for serum iron concentration in patients receiving such therapy. Values determined by atomic absorption spectroscopy were usually much higher than those obtained by either a manual or an automated colorimetric procedure, and also were higher than the total serum iron-binding capacity of the same sera. This difference is attributed to circulating iron being present both as iron dextran as as transferrin-bound iron. We conclude that atomic absorption spectroscopy should be used to determine serum iron in patients receiving Imferon.
Radioimmunoassay of bile acids in serum.
Authors: Demers L M , Hepner G
Published: January 2020

We developed four radioimmunoassay procedures for the determination of glycine-conjugated bile acids in serum. Antibodies to two primary bile acids, cholylgycine and chenodeoxycholylglycine, and to two secondary bile acids, sulfolithocholylglycine and deoxycholylglycine, were raised in rabbits after the acids were covalently linked to albumin by use of the carbodiimide reaction. Assay sensitivity for each of these bile acids is in the picomole range with the standard curve extending from 10-80 pmol. The concentration of bile acids in serum increased in various states of liver disease and its measurement appears to be an extremely sensitive indicator of liver function.
Method for measuring the concentration of urinary proteins according to their molecular size category.
Authors: Pesce A J , Hsu A , Kornhauser C , Sethi K , Ooi B S , Pollak V E
Published: January 2020

We combined the use of a concentrating device (Minicon) and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate to semi-quantitate the concentration of (a) the collective low-molecular-weight proteins and (b) of albumin excreted in the urine of patients after renal transplantation. Analytical recovery of many serum proteins from samples concentrated 100-fold in the Minicon apparatus was about 70%. It was possible to examine many urine samples by polyacrylamide gel electrophoresis after concentration with this device. The reproducibility (CV) of the technique was on the order of 20% when albumin and low-molecular-weight protein were in about equal concentration. The method was adequate to differntiate glomerular and tubular proteinuria, because in glomerular proteinuria the ratio of albumin to low-molecular-weight proteins is about 20/1, whereas in tubular proteinuria the ratio is about 1/1.
Specificity and reproducibility of acetone precipitation in identifying surface-active phosphatidylcholine in amniotic fluid.
Authors: Penney L L , Hagerman D D , Sei C A
Published: January 2020

We show the thoretical and actual variability in the amount of surface-active lecithin precipitated in the acetone-precipitation step of determining lecithin/sphingomyelin (L/S) ratios in the clinical laboratory. Lecithins precipitated may range from 60 to 90% of the total surface-active lecithins present. The range is sufficient to account for the occasional "immature" L/S ratios (less than 2/1) found in amniotic fluid from women bearing mature fetuses.
Detection of drugs of abuse by radioimmunoassay: a summary of published data and some new information.
Authors: Cleeland R , Christenson J , Usategui-Gomez M , Heveran J , Davis R , Grunberg E
Published: January 2020

We review the status of radioimmunoassays for detection of abused drugs. Individual assays with use of 125I-labeled antigens are all performed in an identical manner and can be completed in 30 min to 1 h. Combined assays for simultaneous detection of two or more such drugs or assays in which a tritium-labeled antigen is used require 1-2 h for completion. All tests can be performed with 0.1 ml or less of specimen. The assays involving 125I reliably detect urinary concentrations of, per liter, 40-100 mug of morphine, 100 mug of barbiturates, methadone, methaqualone, or benzoylecgonine, and 1000 mug of amphetamine. The assay for morphine involving 3H detects 60 mug/liter. Each assay is capable of providing a qualitative and quantitative estimate of the drugs sought. The 125I-labeled antigens have a usable shelf life of at least two to four months after the antigen is iodinated; the tritium assay is stable for six months. The assays can be performed with use of paper discs that have been suspended in urine and then dried, in place of the liquid specimen. The assays appear to be equally applicable to detection of drugs in urine, blood, saliva, and tissues. All of them are done at ambient temperature and can be used equally well for emergency (stat) tests or mass screening. Except for the benzoylecgonine assay, the clinical reliability of these tests has been demonstrated.
Gas-chromatographic analysis for therapeutic concentrations of amitriptyline and nortriptyline in plasma, with use of a nitrogen detector.
Authors: Bailey D N , Jatlow P I
Published: January 2020

We describe a gas-chromatographic procedure for the simultaneous determination of amitriptyline and its active metabolite, nortriptyline, in therapeutic concentrations in human plasma, with use of a nitrogen detector. Both drugs are extracted at pH 10.5 into hexane/isoamyl alcohol, back-extracted into dilute HCl, and re-extracted into hexane/isoamyl alcohol after alkalinization of the HCl. The solvent is evaporated and the residue gas-chromatographed. Protriptyline is used as the internal standard. As little as 5 mug of amitriptyline or nortriptyline can be detected per liter of plasma. The coefficients of variation, for a concentration of 200 mug/liter, are 4.6% and 4.3% within-day and 8.6% and 3.4% day-to-day for amitriptyline and nortriptyline, respectively. The procedure was applied to patients receiving therapeutic doses of both drugs and also to patients who had taken overdoses of amitriptyline.
Enzymatic assay for methotrexate in serum and cerebrospinal fluid.
Authors: Falk L C , Clark D R , Kalman S M , Long T F
Published: January 2020

We describe an assay for methotrexate in biological fluids. The assay is based on inhibition by methotrexate of dihydrofolate reductase from Lactobacillus casei. The lower limit of sensitivity in serum is 2 X 10(-8) mol (about 10 mug) of methotrexate per liter. Within-run precision is +/- 5% (coefficient of variation) and day-to-day variation is 18%. Advantages of the assay are ease of manipulation, high sensitivity, and specificity.
Rapid gas-chromatographic measurement of anticonvulsant drugs in serum.
Authors: Dorrity F , Linnoila M
Published: January 2020

We describe a rapid method for precisely measuring concentrations of anticonvulsant drugs in serum. The simple procedure, adaptable to the clinical laboratory, can be used for the routine simultaneous measurement in sera of phenobarbital, primidone, dephenylhydantoin, and (or) ethosuximide. The extraction procedure requires no solvent evaporation and gives a good yield for primidone and quantitative extraction for the other drugs. The relatively small amount of "early phenobarbital" formed during on-column methylation permits a precise analysis of phenobarbital based on a single peak. Results can be made available directly, without manual measurements or calculations.
Quantitative gas-chromatographic flame-ionization method for p-chlorophenoxyisobutyric acid in human serum and saliva.
Authors: Connor J N , Johnson G F , Solomon H M
Published: January 2020

We describe a gas-chromatographic method for p-chlorophenoxyisobutyric acid (I) the active metabolite of clofibrate. The drug and internal standards are separated from either serum or saliva by a double extraction procedure and converted to the corresponding butyl esters by reaction with iodobutane in a mixture of methanol and N,N-di-methylacetamide containing tetramethylammonium hydroxide. Within-run CV of this assay at a serum I concentration of 79.2 mg/liter was 2.3% and at a salivary I concentration of 2.5 mg/liter was 2.1%. Precision during four months of the serum and salivary assays at these concentrations was 4.1% and 6.2%, respectively. The mean serum concentration of I (12 h after dose) in patients receiving the drug at an average dose of 28.0 mg/kg per day was 109.6 mg/liter. Serum and salivary concentrations of I as determined by our procedure were used to calculate the unbound fraction of drug in human serum. Such measurements can be used to monitor therapy in patients with renal disease, where drug toxicity may arise from high concentrations of unbound I.
Simplified fluorometric assay for diphenylhydantoin in plasma.
Authors: Dill W A , Leung A , Kinkel A W , Glazko A J
Published: January 2020

The fluorometric benzophenone procedure for diphenylhydantoin has been simplified by eliminating the need for preliminary extraction of plasma with an organic solvent. Assays are done directly on 0.2 ml of plasma by treating it with alkaline permanganate to form benzophenone, extracting the benzophenone with heptane, and then shaking the heptane layer with sulfuric acid and measuring the fluorescence of the acid layer. The assay is highly reproducible, and adequately sensitive to detect 1 mug of the drug per milliliter of plasma. Fluorometric and gas-liquid chromatographic assays of 154 plasmas gave results that were not significantly different, even in the presence of phenobarbital, other barbiturates and anticonvulsant drugs, or of various tranquilizers and other commonly used drugs. The assay is rapid, the unit cost per assay low.
Beta-carotene content of certain organs from two patients receiving high doses of beta-carotene.
Authors: Mathews-Roth M M , Abraham A A , Gabuzda T G
Published: January 2020

We measured carotene in the livers of two patients receiving beta-carotene therapy for photosensitivity. In both patients, the amount of carotene was within reported ranges for patients on normal diets; no abnormal amounts of beta-carotene had accumulated in the livers after oral administration of large amounts of beta-carotene. Light-microscopic examination of the liver (specimen obtained at cholecystectomy) of one patient with erythropoietic protoporphyria and cholesterosis showed findings characteristic of these conditions. Electron-microscopically, semicrystalline inclusions were seen in the mitochondria of the hepatocytes; such inclusions have been reported in several conditions, including erythropoietic protoporphyria and porphyria cutanea tarda, and in control subjects. Microscopic examination of the liver of the other patient, who had Rothmund-Rhomson syndrome and died of acute bacterial meningitis, revealed no abnormalities. The cerebrum of the latter patient contained 13 mug of carotene per kilogram (wet weight) of brain. No previous report of analysis of human brain for carotenoids could be found.
Studies of the reliability of constituent target values established in a large inter-laboratory survey.
Authors: Grannis G F
Published: January 2020

Lyophilized serum specimens were manufactured in such a way that fixed quantitative interspecimen relationships were established. The specimens were analyzed for about twenty constituents by several thousand laboratories in 1971, 1972, and 1973. Most of the consensus mean values derived from these analyses were found to relect accurately the relationships established in the manufacture of the specimens. In addition, analyses of some of the specimens for calcium by the National Bureau of Standards confirmed the relationships. I conclude that the consensus mean values derived for most constituents are reproducible and any biases that may be present are consistent from survey to survey.
Ultramicro gas-chromatographic analysis for anticonvulsants, with use of a nitrogen-selective detector.
Authors: Vandemark F L , Adams R F
Published: January 2020

We describe a procedure for determining phenobarbital, primidone, and diphenylhydantoin simultaneously in 50-mul volumes of serum by use of gas chromatography and a detector with heightened sensitivity and selectivity for nitrogenous compounds. The drugs, together with an internal standard, 5-allyl-5-phenyl barbituric acid, are extracted from serum by the procedure of MacGee [Anal. Chem. 42, 421 (1970)]. The drugs are converted to their methyl derivatives by a modification of the procedure of Greeley [Clin. Chem. 20, 192 (1974)] and then analyzed on a column containing 3% OV-1, with a temperature program, and detected by a nitrogen-selective detector. The method is reproducible to about 7%. Sensitivities of 0.5 mg/liter for 50-mul serum samples are attained routinely. Mephobarbital interferes with the analysis because methylation yields the same product as methylated phenobarbital. Total analysis time for a single sample is 15 min.
Determination of erythrocyte folate by competitive protein binding assay preceded by extraction.
Authors: Mortensen E
Published: January 2020

Determination of the concentration of erythrocyte folate by means of competitive protein binding assay critically depends on the extraction procedure applied. Results will be influenced by variable factors such as the in vitro age of the blood samples, the degree of hemolysis, the presence of ascorbic acid, and the pH during extraction and elimination of proteins. The radioassay is strongly influenced by the pH of the final reaction mixture, the method used to separate free and protein-bound molecules, and the molecular configuration of the folates present. Based on experimental results presented, I describe a method for the determination of erythrocyte folate.
X-Prolyl dipeptidyl-aminopeptidase activity, with X-proline p-nitroanilides as substrates, in normal and pathological human sera.
Authors: Hino M , Fuyamada H , Hayakawa T , Nagatsu T , Oya H
Published: January 2020

X-Prolyl dipeptidyl-aminopeptidase (no EC no. assigned) activity in normal and pathological human sera was assayed with several newly synthesized X-proline p-nitroanilides as chromogenic substrates. Normal values for 88 healthy subjects (15 to 81 years old), with glycylproline p-nitroanilide as substrate at pH 8.7, were 54.9 +/- 1.5 (SE) (range, 25.7 - 96.0) mumol/min per liter of serum at 37 degrees C. The results suggest that the enzyme activities with all X-proline p-nitroanilides were increased in patients with hepatitis and decreased in patients with gastric cancer. On Sephadex G-200 column chromatography, normal human sera showed a single peak of enzyme activity with glycylproline p-nitroanilide as the substrate, which coincided with the peak with glycylproline beta-naphthylamide but was different from the peaks with leucine beta-naphthylamide. Sera from patients with hepatitis or liver cirrhosis showed an increase in the normal peak and the appearance of another new peak with glycylproline p-nitroanilide as substrate.
Urinary organic acids in man. I. Normal patterns.
Authors: Lawson A M , Chalmers R A , Watts R W
Published: January 2020

We studied qualitative pattern of urinary acidic metabolites excreted by normal persons. The results provide a basis on which to compare results for patients with potentially abnormal organic acidurias. A series of urinary polyhydroxy (aldonic and deoxyaldonic) acids has been identified. Most of these compounds have not been previously reported in human urine, except in connection with the present work, and are additional to the previously recognized urinary organic acids, which were also observed. Possible metabolic origins of some of the acids are briefly discussed.
Urinary organic acids in man. II. Effects of individual variation and diet on the urinary excretion of acidic metabolites.
Authors: Chalmers R A , Healy M J , Lawson A M , Watts R W
Published: January 2020

We have assessed individual variations in urinary acidic metabolite excretion and the effects of extreme alterations in dietary composition on these metabolites in selected normal persons who we considered representative of the general ambulant normal population. Extreme dietary alterations produced relatively small changes in the patterns or amounts of metabolite excretion, but large individual within-subject variations were observed. Our results indicate that variation in the ranges of excretion for the normal population mainly depend on individual metabolic variations rather than on dietary factors, and provide a basis for the assessment of the normal ranges determined from population surveys. Our results are discussed in relation to previous studies on the variability of urinary acidic metabolite excretion in man.
Analysis of whole blood by neutron activation: a search for a biochemical indicator of neoplasia.
Authors: Zdankiewicz D D , Fasching J L
Published: January 2020

We determined a total of 13 elements in the whole blood of cancer patients and controls by using instrumental neutron activation analysis. The samples were spotted as whole blood on small filter paper disks, allowed to dry at room temperature, and sealed between two polyethylene disks. They were then irradiated and counted. Eleven elements were determined by this method. Sodium and chlorine were measured by irradiating whole blood in polyethylene vials. Statistical analysis of the data predicts that, with a very hgih probability, cobalt and iron are lower, adn sodium, tantalum, lanthanum and chlorine are higher in the cancer patients than in the normal persons tested. Chromium, zinc, and bromine also show differences between the two groups at a probability exceeding 0.95. Variations are indicated in scandium and cesium also, but are less strongly supported. Hafnium and selenium show no significant differences.
Competitive enzyme-liked immunoassay with use of soluble enzyme/antibody immune complexes for labeling. I. Measurement of human choriogonadotropin.
Authors: Yorde D E , Sasse E A , Wang T Y , Hussa R O , Garancis J C
Published: January 2020

We described the principle of a new enzyme-immunoassay, competitive enzyme-liked immunoassay (CELIA), for quantitative measurement of soluble antigens and haptens. In the assay, binding of antibody to antigen-immunosorbent is competitively inhibited by the free antigen to be measured. The amount of first antibody bound to the immunosorbent is measured by an enzymatic technique in which a heterologous bridging antibody and a soluble antibody/enzyme immune complex are applied in sequence. The soluble complex we used was rabbit antiperoxidase/horseradish peroxidase. Peroxidase activity is inversely proportional to the concentration in the original sample of the substance to be assayed. The enzyme-linked reagents are potentially widely applicable to any substance to be measured. To demonstrate the feasibility of CELIA, we report a preliminary study of its application to the measurement of human chloriogonadotropin in serum and urine. The assay described for this hormone has a working range of 1 to 50 int. units per milliliter of sample. The technique obviates the disadvantages associated with measurement and handling of radioisotopes in radioimmunoassays and the only major instrumentation required is a centrifuge and a conventional spectrophotometer.
Modified nucleosides in urine: selective removal and analysis.
Authors: Uziel M , Smith L H , Taylor S A
Published: January 2020

Because excretion of certain nucleosides increases in all types of cancer, detection and treatment of the disease would be enhanced by rapid, simple quantitation of such nucleotides. To facilitate these analyses in urine, we have prepared a specific adsorbent for nucleosides. The affinity adsorbent gel contains an immobilized phenylboronic acid group that specifically binds cis-diols, as in ribonucleosides, which can then be quantititatively recovered by elution with acetic acid. The advantage of this boronate gel over other preparations lies in its high capacity in the swollen state (0.26 mmol/ml), so that only small volumes (less than 1 ml) of gel are required for assays. Nucelosides containing a free diol group on the ribosyl group are retained at pH 8.8 in 0.25 mol/liter salt solution with a retention volume of 15 or larger, as compared with values of 1 to 2 for the free bases. Negatively charged species (not including the boronate complex) are eluted earlier than neutral or cationic species. Added nucleosides (neutral, cationic, or anionic) are quantitatively recovered. Because pseudouridine is eluted in a unique position, this property has been used to measure it in urine. The procedures used are chemically mild. For example, we have confirmed the observation of Fink and Adams [Arch. Biochem. Biophys. 126, 27 (1968)] that urine contains N1-methyladenosine and not N6-methyladenosine, the alkaline rearranged product.
Erythrocyte porphobilinogen synthase (delta-aminolaevulinate dehydratase) activity: a reliable and quantitative indicator of lead exposure in humans.
Authors: Mitchell R A , Drake J E , Wittlin L A , Rejent T A
Published: January 2020

We assessed optimal conditions for assay of porphobillinogen synthase (EC 4.2.1.24) activity in human blood containing abnormally high concentrations of lead. Zn2+and -SH, both required for complete activation of the enzyme, had additive effects. Using a modified method based on these studies, we found blood lead concentration to be strictly proportional to ln(activated/nonactivated) enzyme activity. One brand of commercially available "lead-free" tubes contained a substance that interfered with this relationship. In vitro studies, with the modified assay, showed ALAD to be activated by low concentrations but inactivated by high concentrations of Hg2+, Cd2+, and ethylenediaminetetraacetate. We fouund no genetically influenced differences among unexposed individuals when in(activated/nonactivated) enzyme activities were compared. The technique is suitable for use in screening for lead poisoning in humans.
New approach to determination of total ketone bodies in serum.
Authors: Siegel L , Robin N I , McDonald L J
Published: January 2020

We describe a one-step assay for total ketone bodies in serum. D-BETA-Hydroxybutyrate is enzymatically oxidized by NAD+ to acetoacetate. This thermodynamically unfavorable reaction is driven to completion by coupling it with the enzymatic reduction of pyruvate by NADH. The acetoacetate so formed, as well as the pre-existing acetoacetate, is quantitatively decarboxylated to acetone in a gas chromatograph and measured directly. Thus by a single measurement for acetone, all three ketone bodies are simultaneously determined. In light of the ubiquity of situations associated with augmented ketone body production, the clinical implications of this approach are extensive.
Performance characteristics of rules for internal quality control: probabilities for false rejection and error detection.
Authors: Westgard J O , Groth T , Aronsson T , Falk H , de Verdier C H
Published: January 2020

When assessing the performance of an internal quality control system, it is useful to determine the probability for false rejections (pfr) and the probability for error detection (ped). These performance characteristics are estimated here by use of a computer stimulation procedure. The control rules studied include those commonly employed with Shewhart-type control charts, a cumulative sum rule, and rules applicable when a series of control measurements are treated as a single control observation. The error situations studied include an increase in random error, a systematic shift, a systematic drift, and mixtures of these. The probability for error detection is very dependent on the number of control observations and the choice of control rules. No one rule is best for detecting all errors, thus combinations of rules are desirable. Some appropriate combinations are suggested and their performance characteristics are presented.
Combined Shewhart-cusum control chart for improved quality control in clinical chemistry.
Authors: Westgard J O , Groth T , Aronsson T , de Verdier C H
Published: January 2020

We describe the adaptation of the decision limit cumulative sum method (cusum) to internal quality control in clinical chemistry. With the decision limit method, the cusum is interpreted against a numerical limit, rather than by use of a V-mask. The method can be readily implemented in computerized quality-control systems or manually on controls charts. We emphasize the manual application here and demonstrate how the technique can be implemented on existing Shewhart or Levey-Jennings control charts. This permits both cusum and Shewhart control rules to be used simultaneously on a single control chart and also minimizes the data calculations necessary for the cusum method. Computer simulation studies are used to determine the performance characteristics of several different cusum rules, alone and in combination with a Shewhart rule. These studies indicate that improvements in existing quality-control systems should be possible by addition of this simple cusum method and by use of a combined Shewhart-cusum control chart. This should be particularly advantageous when introducing the cusum method in laboratories with manual quality-control systems.
Presence of creatine kinase BB isoenzyme in some patients with prostatic carcinoma.
Authors: Feld R D , Witte D L
Published: January 2020

We have observed creatine kinase isoenzyme BB in the sera of nine of 19 patients with Stage D carcinoma of the prostate. Its presence does not seem to correlate with acid phosphatase activity in serum or the presence of bone metastases as indicated by increased alkaline phosphatase activity in serum. Only three of the nine patients with BB isoenzyme activity detectable in their serum had abnormal values for total creatine kinase activity, but all had abnormal values for alkaline and acid phosphatase activity. All 10 patients with no BB isoenzyme detectable had abnormal acid phosphatase values; however, only seven had increased alkaline phosphatase values and only one had increased creatine kinase activity.
High-performance liquid-chromatographic analysis for tryptophan in serum.
Authors: Krstulovic A M , Brown P R , Rosie D M , Champlin P B
Published: January 2020

Concentrations of total tryptophan were determined rapidly and sensitively in 50 microliter of serum by a reversed-phase partition version of high-performance liquid chromatography. For determination of total tryptophan, sample preparation requires only precipitation of the serum protein with trichloroacetic acid and removing excess trichloroacetic acid with a 1,1,2-trichlorotrifluoroethane(Freon)/tri-N-octylamine solution. Tryptophan in serum samples was detected by ultraviolet and fluorescence spectrometry. No interferences from the naturally occurring constituents of serum were observed. Elution time for tryptophan is 15 min, the limit of detection is 1 pmol.
Radioimmunoassay of parathyroid hormone (parathyrin) in monkey and man.
Authors: Hargis G K , Williams G A , Reynolds W A , Kawahara W , Jackson B , Bowser E N , Pitkin R M
Published: January 2020

A radioimmunoassay for rhesus monkey and human immunoreactive parathyrin was developed in which a selected anti-bovine parathyrin antiserum, radioiodinated purified bovine parathyrin tracer, and human parathyroid tissue-culture media standards were used. The resulting data indicate that (a) the method is sensitive, specific, accurate and reproducible; (b) it is valid for both the rhesus monkey and the human; (c) the serum immunoreactive parathyrin concentration of the monkey is essentially the same as that in man; (d) monkey immunoreactive parathyrin responds to changes in serum calcium concentration similarly to that in man; and (e) the rhesus monkey is therefore a suitable species in which to study parathyroid physiology, from which conclusions can be applied to the human.
New micromethod for measuring cholesterol in plasma lipoprotein fractions.
Authors: Bronzert T J , Brewer H B
Published: January 2020

A method is described for the reliable, fast, and relatively inexpensive fractionation of plasma lipoproteins and quantitation of their cholesterol content. This procedure requires 350 microliter of plasma and can be completed within 3 h. Plasma lipoproteins (175 microliter of plasma) were prestained with Fat Red 7B and centrifuged (Beckman Airfuge) at plasma density (d = 1.006 kg/liter) and at a solvent density of 1.060 kg/liter, adjusted by adding solid KBr. Prestained centrifuged samples demonstrated the characteristic elevation of chylomicrons in phenotypes I and V, low-density lipoproteins of phenotype II, very-low-density lipoproteins in phenotype IV and V, and continuum of pink color throughout the centrifuge tube, diagnostic of the floating beta lipoprotein of type III. Centrifuged samples were separated into top and bottom fractions by aspiration. Cholesterol was quantitated with an enzymic oxygen-electrode analyzer (Beckman Cholesterol Analyzer). Correlation coefficients between cholesterol values for plasma from normal hyperlipidemic individuals obtained with the Beckman Analyzer vs. the Technicon AutoAnalyzer II and SMAC systems were 0.977 and 0.973, respectively.
Hemoglobin interference with Du Pont Automatic Clinical Analyzer procedure for calcium.
Authors: Porter W H , Carroll J R , Roberts R E
Published: January 2020

Hemoglobin in concentrations of approximately 2.5 g/liter or greater significantly increases values for apparent calcium in serum as determined with the Du Pont aca, an interference attributable to the 575-nm absorption band of oxyhemoglobin being uncompensated by the 577--600 nm differential absorption reading of the calcium o-cresolphthalein complexone complex.
High-performance liquid-chromatographic assay for nitrofurantoin in plasma and urine.
Authors: Aufrère M B , Hoener B , Vore M E
Published: January 2020

The high-performance liquid-chromatographic method described here for the quantitative analysis for nitrofurantoin in urine and plasma involves direct analysis of urine samples and analysis of plasma samples after protein precipitation by methanol. The assay, which requires only 0.2 ml of biological fluid and shows a linear relationship in the range 0.02 to 200 mg/liter, can be performed in 9 min and is reproducible (CV less than 2%). Results for nitrofurantoin so obtained correlate well with those obtained by the Hyamine 10-X spectrophotometric method (CV = 2%), but the present method is more sensitive. With no modification, the present procedure can also be used for nitrofurazone. The sensitivity, accuracy, and convenience of the method make it suitable for clinical monitoring and pharmacokinetic/bioavailability studies with 5-nitrofuran derivatives.
Isoelectric focusing of gamma globulins in cerebrospinal fluid from patients with multiple sclerosis.
Authors: Trotter J L , Banks G , Wang P
Published: January 2020

The technique of isoelectric focusing has been adapted for rapid clinical analysis for globulins in cerebrospinal fluid with use of commercially prepared horizontal-slab acrylamide gels. The globulin fraction is concentrated by ammonium sulfate precipitation, which allows more of the relevant protein to be applied, use of a wider range of total protein concentrations, and higher resolution than is true for previously described methods. Critical variables include a constant concentration and volume of IgG, a constant low temperature of the acrylamide gel, and sensitive staining with Coomassie Brilliant Blue G-250. The apparatus used is adaptable for other electrophoretic procedures in the clinical laboratory, and the use of commercially prepared gel slabs is more convenient, more reproducible, and requires less time than other methods.
Effectiveness of an outpatient urine screening program.
Authors: Fraser C G , Smith B C , Peake M J
Published: January 2020

We evaluated the effectiveness of a routine outpatient urinalysis screening program on a sample population of 2600 patients. The 189 abnormal urine results found in 182 patients were followed up by study of any new clinical and laboratory investigations or therapeutic modifications initiated on the basis of any abnormal test result. The urinalysis screening program appeared to have significant bearing on diagnosis or treatment in only 13 patients. Abnormalities found in 150 of the 182 patients were either not noted or no further positive action was taken. Thus we concluded that under the conditions of this study the urine screening program added to hospital costs without significant benefit to the patient.
Influence of salts on Michaelis-constant values for NADH.
Authors: Howell B F , McCune S , Schaffer R
Published: January 2020

We previously observed [Clin. Chem. 22, 1648 (1976)] that values of the Michaelis constant for NADH for the conversion of pyruvate to lactate with lactate dehydrogenase (EC 1.1.1.27) in the presence of 0.1 mol/liter buffers at 25 degrees C showed first-order dependence on enzyme concentration. This is now recognized to be the result of an inhibitory influence exerted by buffers [NH4HCO2, tris(hydroxymethyl)aminomethane, and phosphate] and salts [(NH4)2SO4 and NaCl] present in the reaction mixtures. Inhibition constants for the enzyme/inhibitor complexes formed with these substances are about 0.3 mol/liter for competition of NH4HCO3 with NaOH and 0.4 mol/liter for competition of NH4HCO3 with pyruvate; they are 0.6 mol/liter for NaCl, 1.0 mol/liter for sodium phosphate, 0.3 mol/liter for (NH4)2SO4, and 0.8 mol/liter for tris(hydroxymethyl)aminomethane when these substances compete with NADH. Because of the large molar ratio of buffer to substrate (about 10(9):1) in enzymatic assays, the buffer concentration significantly influences the Michaelis constant, despite the large value for the inhibition constant. Attention to the concentrations of these substances may be required for decreasing variability in clinical assays in which lactate dehydrogenase and possible other enzymes are used.
Measurement of free-circulating cis-dichlorodiammineplatinum(II) in plasma.
Authors: Bannister S J , Sternson L A , Repta A J , James G W
Published: January 2020

Dichlorodiammineplatinum(II) is an anti-neoplastic agent that is currently undergoing clinical evaluation. We describe an analytical method for monitoring the free drug (or its breakdown products) in plasma. The method is able to distinguish between free and protein-bound drug. Plasma samples are deproteinized by centrifugal ultrafiltration. The platinum in the ultrafiltrate is converted to a cationic species by reaction with ethylenediamine and then collected on paper impregnated with cation-exchange resin. This process concentrates the samples, increases the stability of the platinum compounds (by removing the compound from solution), and places the sample in a uniform matrix of minimum thickness, which maximizes detection capabilities. Platinum was measured directly on the ion-exchange disks by X-ray fluorescence. The detection limit for free drug is 240 microgram/liter of plasma at the 3s level and fluorescence intensity is linearly related to drug concentration in the range from 570 to 5700 microgram/liter.
Serum gentamicin assay by high-performance liquid chromatography.
Authors: Maitra S K , Yoshikawa T T , Hansen J L , Nilsson-Ehle I , Palin W J , Schotz M C , Guze L B
Published: January 2020

We describe a high-performance liquid chromatographic method for the quantitative determination of gentamicin in serum. The antibiotic was separated from serum by passage through a silicic acid column, derivatized with o-phthalaldehyde, and eluted with ethanol. The derivatized gentamicin was then separated into all three of its major components by reversed-phase chromatography and quantified by fluorometry. Concentrations in serum as low as 0.5 mg of gentamicin per liter could be accurately determined. A standard curve showed a linear response for serum containing gentamicin at concentrations ranging from 0 to 20 mg/liter. Tobramycin, amikacin, ampicillin, penicillin G, methicillin, carbenicillin, chloramphenicol, clindamycin, and cephalothin did not interfere with the gentamicin assay. Comparison with an accepted microbiological assay yielded a correlation coefficient of 0.99. This chemical assay is rapid (less than 30 min), sensitive, accurate, specific, and appears to be applicable to other aminoglycosides.
Use of an enzymatic kit method for cholesterol, designed for continuous-flow instrumentation, with discrete bichromatic and centrifugal analyzers.
Authors: Levinson S S
Published: January 2020

I examined a cholesterol-assay kit ("Autoflo", Biodynamics/bmc) designed for use with continuous-flow instrumentation for its use with some discrete analyzers. At pH 7.2, color develops within 3 min upon exposure to cholesterol, then begins to fade. At pH 8, the color develops more slowly but remains stable for at least 15 min after reaching a maximum. A pH 8.8, the color develops still more slowly and standards and patients' sera behave differently. Reagent at pH 7.2 is preferred because assays can be completed most rapidly, but pH 8 reagent must be used with instruments requiring longer periods of incubation. Cholesterol assays can be performed accurately, rapidly, reproducibly, and at low cost with an Abbott ABA-50 and pH 7.2 reagent or with a Gemeni Centrifugal Analyzer and the pH 8 reagent.
Determination of placental estriol in urine by gas-liquid chromatography, with equilenin as internal standard.
Authors: Gotelli G R , Kabra P M , Marton L J
Published: January 2020

Placental estriol in urine can be determined by rapid enzymatic hydrolysis, extraction with neutral XAD-2 resin, and quantitation by gas-liquid chromatography, with equilenin as the internal standard. Glucose, methenamine mandelate, hydrochlorothiazide, phenolphthalein, or salicylate do not interfere. Analytical recovery of estriol added to urine was 92-108%. Day-to-day precison (CV), established by 15 repilicate analyses at a mean concentration of 21.3 mg/liter, was 6.6%.
History and Background of Protoporphyrin Testing
Authors: Labbé Robert F
Published: January 2020

Lead intoxication was first associated with increased coproporphyrin excretion almost 100 years ago; but not until the 1930's were abnormalities in blood protoporphyrin detected. These later findings have been interpreted as an inhibition by lead of iron incorporation into protoporphyrin during heme synthesis. The testing and application of this hypothesis had to await three more decades of research during which porphyrin/heme biosynthesis was elucidated, control of the pathway was intensively studied, and methodology was greatly improved. The heme biosynthetic pathway is uniquely affected by lead at several sites. These toxic effects can be manifested as increased coproporphyrin and δ-aminolevulinate excretion, decreased erythrocyte δ-aminolaevulinate dehydratase activity, and increased erythrocyte protoporphyrin concentration, all of which have been used and promoted as diagnostic tests for lead intoxication. Among these, the last appears to be becoming the test of choice. The historical background of this development is discussed from a biochemical viewpoint.
Simpler flame photometric determination of erythrocyte sodium and potassium: the reference range for apparently healthy adults.
Authors: Mayer K D , Starkey B J
Published: January 2020

Separated erythrocytes are washed repeatedly with iso-osmolar magnesium chloride solution, lysed by adding saponin, and sodium potassium measured in the diluted hemolysate by flame photometry. The coefficient of variation for the method was less than 4%. Reference intervals determined for a healthy population and hospitalized (elective surgery) patients without electrolyte disorders were 4.6-7.8 mmol/liter for erythrocyte sodium concentration and 94-110 mmol/liter for erythrocyte potassium concentration (2.5-97.5 percentiles).
Compensation by zinc chelation for fluorescent background in determining coproporphyrin and uroporphyrin in urine.
Authors: Lavallee D K , Norelius J T
Published: January 2020

An improved method for separation and fluorescent analysis of coproporphyrin and uroporphyrin in urine was presented by Sobel, Cano, and Thiers [Clin. Chem. 20, 1397 (1974)]. Accurate determination of porphyrin concentrations by this method is impeded by the fluorescent background in urine samples, which varies from one specimen to another. By use of a straightforward procedure, zinc may be incorporated into coproporphyrin and uroporphyrin. Measurement of the difference in the fluorescent emission intensity at 650 nm for the porphyrin solutions before and after zinc incorporation compensates for fluorescent background and gives a more accurate determination.