bluuebunny/crossref_metadata_2025 huggingface dataset:
The unique lipoprotein(a): properties and immunochemical measurement
Authors: Albers J J , Marcovina S M , Lodge M S
Published: January 2020

Lipoprotein (a) [Lp(a)] represents a class of lipoprotein particles defined by the presence of apolipoprotein(a), a unique glycoprotein linked by a disulfide bond to apolipoprotein B-100 to form a single macromolecule. Apolipoprotein(a) is formed by three different structural domains having high amino acid sequence homology with plasminogen. One of the domains, called kringle 4, is present in multiple copies, the number of which varies and is genetically determined. This accounts for the size heterogeneity of apolipoprotein(a) and thus of Lp(a). Because high concentrations of Lp(a) are associated with atherosclerotic cardiovascular and cerebrovascular disease and may inhibit fibrinolysis, interest in measuring Lp(a) has increased considerably, leading to a rapid development of commercially available immunoassays for the measurement of Lp(a) in human plasma. However, the immunochemical measurement of Lp(a) has several peculiar problems in addition to those encountered by the measurements of other apolipoproteins. The major problems that need to be carefully evaluated are (a) the structural complexity and heterogeneity of Lp(a), (b) the homology of apolipoprotein(a) with plasminogen, (c) the lack of standardization of the methods, and (d) the lack of a common means of expressing the Lp(a) values.
Discordance between measured and calculated total carbon dioxide
Authors: Ungerer J P , Ungerer M J , Vermaak W J
Published: January 2020

Recent studies on the agreement and correlation between measured and calculated total CO2 (TCO2) have yielded conflicting results. Pre-analytical variation could have been partially responsible. While keeping such variables at an absolute minimum, we found excellent correlation (r = 0.98) in 88 samples, with only a small variation in agreement between measured and calculated TCO2 values (SD = 1.1 mmol/L), which could be a function of variation in apparent pK (pK'). A subsequent evaluation of 913 consecutive samples, routinely analyzed, yielded similar results. These results suggest that some of the discrepancies reported in the literature could be ascribable to differences in sample types and sample handling. Rigid control of pre-analytical procedures is therefore a prerequisite in studies on this topic. The two methods were found to agree over a wide range of values, such that either of them could be used to evaluate clinical acid-base status accurately.
On dividing reference data into subgroups to produce separate reference ranges
Authors: Harris E K , Boyd J C
Published: January 2020

We consider statistical criteria for partitioning a reference database to obtain separate reference ranges for different subpopulations. Using general formulas relating population variances, sample sizes, and the normal deviate test for the significance of the difference between two subgroup means, we show that partitioning into separate ranges produces little reduction in between-person variability, even when the differences between means are highly significant statistically. However, when there is a clear physiological basis for distinguishing between certain subgroups, simulation studies show that partitioning may be necessary to obtain reference limits that cut off the desired proportions of low and high values in each subgroup. Guidelines based on these results are provided to help decide whether separate ranges should be obtained for a given analyte.
Cross-reactivity of monomeric and dimeric biosynthetic human growth hormone in commercial immunoassays
Authors: Bowsher R R , Apathy J M , Ferguson A L , Riggin R M , Henry D P
Published: January 2020

Commercial kits give different measurements for concentrations of growth hormone (GH, somatotropin) in serum. Most notably, a two-site monoclonal-antibody-based immunoradiometric assay (IRMA) from Hybritech routinely yields lower values than do conventional RIAs in which polyclonal antibodies are used. We used purified dimeric biosynthetic human GH as a model compound to investigate the specificity of five commercial immunoassays for size variants of GH. In all five assays, biosynthetic monomeric GH was significantly more potent than pituitary-derived standard GH supplied with the kits. Dimeric GH was significantly less potent than monomer in four of the five assays, and cross-reactivities varied more than fivefold, from 15% to 84%. Using three commercial kits selected for their specificity for dimeric GH, we measured GH in serum samples from 18 normal adults. The mean GH concentrations in serum--0.7 (Hybritech, IRMA), 1.8 (Diagnostic Products, RIA), and 3.1 (Cambridge, RIA) micrograms/L--differed significantly, but in the same rank order as that obtained in the experiments on dimer cross-reactivity.
Massive theophylline overdose with atypical metabolic abnormalities
Authors: Eshleman S H , Shaw L M
Published: January 2020

We report a case of fatal theophylline overdose in a 16-year-old asthmatic boy who presented with seizures, respiratory arrest, and a theophylline concentration of 117 mg/L in serum. His hospital course was complicated by refractory hypotension and severe ischemic necrosis of skeletal muscle, bowel, and liver. The metabolic abnormalities observed early in his hospital course included severe hyperkalemia, hyperphosphatemia, hypermagnesemia, hypocalcemia, and profound metabolic acidosis. These metabolic abnormalities differ from those previously reported in cases of massive theophylline overdose. The metabolic abnormalities observed in this patient probably reflected his extensive ischemic tissue damage with release of intracellular ions and associated acidemia. Markedly increased catalytic activities of creatine kinase, aspartate aminotransferase, and alanine aminotransferase in serum were also noted.
Measurement of glutathione S-transferase pi isoenzyme in plasma, a possible marker for adenocarcinoma of the lung
Authors: Howie A F , Douglas J G , Fergusson R J , Beckett G J
Published: January 2020

Using a specific radioimmunoassay, we measured glutathione S-transferase (GST; EC 2.5.1.18) pi isoenzyme in the plasma of 29 patients diagnosed as having carcinoma of the bronchus. Concentrations of the enzyme were significantly higher (P less than 0.01) than those measured in a control group of 16 patients with respiratory disorders other than malignancy. Although, overall, only 19 (66%) of patients with cancer of the bronchus had increased concentrations of GST pi in plasma, eight of the nine (89%) patients diagnosed as having adenocarcinoma had above-normal concentrations of GST pi. To obviate spuriously high results for GST pi concentrations caused by platelet release, we assayed blood samples collected in "Thrombotect" tubes, which contain inhibitors of platelet activation.
Light-chain ratios of immunoglobulins G, A, and M determined by enzyme immunoassay
Authors: Chui S H , Lam C W , Lai K N
Published: January 2020

We describe an enzyme-linked immunosorbent assay for determination of light-chain ratios for IgG, IgA, and IgM in serum. A commercial serum with known overall kappa and lambda concentrations was used as standard. To capture the respective immunoglobulins, we used antibodies to gamma, lambda and mu chains coated onto microtiter plates. Peroxidase-conjugated anti-kappa and anti-lambda chain antisera were reacted with light chains on the captured immunoglobulins, and the amount of enzyme bound was monitored with o-phenylenediamine and urea-hydrogen peroxide as substrates. Calculation of absorbance ratios allowed determination of kappa and lambda chain concentrations of individual immunoglobulins in the standard and samples. Within-run and between-run CVs (n = 25) ranged from 5.9% to 13.0% for "high," "normal," and "low" kappa/lambda ratios for IgG, IgA, and IgM. The thoroughness of light-chain detection, expressed as, e.g., (IgA kappa + IgA lambda)/(total IgA), for 150 sera was 91-110%. The detection limit was 1 microgram/L. Reference intervals (mean +/- SD) for kappa/lambda ratios in sera from 100 apparently healthy adults were 2.34 +/- 0.80 for IgG, 1.59 +/- 0.40 for IgA, and 1.86 +/- 0.76 for IgM.
Electron-capture gas chromatography as a sensitive method for measuring subnanogram amounts of cholesterol in saliva and urine
Authors: Schwertner H A , Johnson E R , Lane T E
Published: January 2020

This is a sensitive method, suitable for measuring subanogram amounts of cholesterol. Cholesterol and the internal standard, epicoprostanol (5-beta-cholestan-3-alpha-ol), are derivatized with pentafluorobenzoyl chloride and detected by electron-capture gas chromatography. The pentafluorobenzoyl esters of cholesterol and the internal standard are easily formed and possess excellent chromatographic and electron-capturing properties. The lower limit of detection of the method, approximately 100 pg injected, is about 500-fold as sensitive as chromatographic methods involving flame-ionization detection. Within-day and between-day coefficients of variation were 4.2% and 8.2%, respectively, for determinations of a urinary cholesterol concentration of 570 micrograms/L (1.47 mumol/L). Such sensitivity permits analysis for cholesterol in (e.g.) physiological fluids, tissue samples, and cell cultures that contain very low concentrations of cholesterol.
Liquid-chromatographic determination of amiodarone and N-desethylamiodarone in serum
Authors: Ou C N , Rognerud C L , Duong L T , Frawley V L
Published: January 2020

We have developed a stable and simple normal-phase liquid-chromatographic method for simultaneously measuring amiodarone and its metabolite, N-desethylamiodarone, within 8 min. The chromatographic system consists of a 15 cm x 3.9 mm Waters "Resolve" silica column and a mobile phase of ammonium sulfate (17 mmol/L, pH 6.8) and methanol (8/92 by vol), pumped at 1.8 mL/min and monitored at 254 nm. After 250 microL of serum is mixed with 100 microL of 0.36 mol/L NaH2PO4, 100 microL of the internal standard solution (L8040, 6 mg/L), and 200 microL of isopropyl ether, the mixture is vortex-mixed and centrifuged. Fifty microliters of the organic layer is injected onto the column. Relative recovery was 100% over the assay range of 0.1 to 20.0 mg/L for both compounds. Within-run and total (day-to-day) CVs were 3% and 7% for amiodarone and 5% and 8% for N-desethylamiodarone, respectively.
Optimal sites and depths for skin puncture of infants and children as assessed from anatomical measurements
Authors: Reiner C B , Meites S , Hayes J R
Published: January 2020

Postmortem measurements were made of distances from skin surface to underlying bone/cartilage on 43 children (up to 8 y old; weights from 0.7 to 26.4 kg) to determine optimal sites and lengths of lancet tips for skin puncture of the heel, great toe, and middle finger. For measuring depths, a needle-like probe was devised that minimized disfigurement. As long as the infant's heel was available for puncture prior to callus formation (to about six months), it offered the greatest depth and the bone/cartilage of the lateral/medial sites was considerably deeper than posterior sites. At age six months, the mean distance of skin surface. At age six months, the mean distance of skin surface to bone/cartilage in the middle finger was 2.5 mm, the lower 95% prediction interval being 1.5 mm. Lengths of lancet tips for finger puncture should therefore be made less than 1.5 mm. To get the desired volumes of blood, a compromise must be reached between depth and width of the lancet tip.
Biological factors affecting concentrations of serum LpAI lipoprotein particles in serum, and determination of reference limits
Authors: Steinmetz J , Choukaife A , Visvikis S , Henny J , Siest G
Published: January 2020

We used an electroimmunoassay to measure LpAI lipoprotein particles (lipoproteins containing apolipoprotein AI but not apolipoprotein AII) in serum of a presumably healthy population of about 1000 subjects, noting sex- and age-related variations for the age interval four to 70 years. Results were higher for women than men. For males, the value for the 50th percentile of the distribution was highest in the 10- to 14-year subgroup, 0.69 g/L, decreasing to 0.60 g/L in adults. For females, the values increased regularly, from 0.59 g/L at ages four to 10 years to 0.79 g/L after age 55 years. The influence of puberty, menopause, oral contraceptives, alcohol consumption, and morphometric characteristics was studied. Only being overweight by more than 20% statistically influenced LpAI values in men and in women. We used these results to select a reference population and to establish reference limits of LpAI at ages 25 to 35 years: 0.40-0.95 g/L for men and 0.46-1.05 g/L for women.
Multivariate interpretation of laboratory tests used in monitoring patients
Authors: Slotnick H B , Etzell P
Published: January 2020

This study demonstrates an approach to the problem of minimizing false-negative and false-positive laboratory findings. In this approach, we consider the fact that results of laboratory tests are correlated, utilize within-person test results to interpret current results, and minimize the impact of multivariate conservatism by examining test results in small groups. The procedure requires panels of tests to be divided into related subpanels, testing each subpanel independently, and using the Bonferroni inequality to determine whether any of the observed values for a given subpanel is "out-of-range." The procedure is demonstrated, and its limitations are observed and discussed.
Accuracy and precision of methods for theophylline measurement in physicians' offices
Authors: Cook J D , Platoff G E , Koch T R , Knoblock E C
Published: January 2020

We tested the accuracy and precision of five theophylline methods intended for use in physicians' offices. The Syntex AccuLevel, Ames Seralyzer, and 3M Diagnostics TheoFAST methods were less reproducible (CVs 6.3% to 9.2%) than the Abbott Vision and Kodak DT-60 (CVs 2.2% to 3.3%). Caffeine interfered with the Vision, Seralyzer, and AccuLevel methods, and theobromine interfered with the Vision, Seralyzer, and TheoFAST methods. Only the DT-60 method was free from interference from any of the 24 compounds tested. Results by all methods correlated well with those by the HPLC comparison method (Clin Chem 1981;27:1931-3) and by the Abbott TDx method for assay of 100 serum (or, when appropriate, paired whole-blood) samples. The frequency of sample results differing from the comparison method by greater than 2.0 mg/L was as follows: TDx, 11%; Vision (serum), 12%; Vision (whole blood), 18%; DT-60, 14%; AccuLevel, 18%; Seralyzer, 25%; and TheoFAST, 31%. The Kodak DT-60 method was the most nearly accurate and precise among these physician's office methods. Some physician's office methods for theophylline analysis are not adequate to guide dosage adjustments.
Evaluation of long-term frozen storage of plasma for measurement of high-density lipoprotein and its subfractions by precipitation
Authors: Nanjee M N , Miller N E
Published: January 2020

The concentration of high-density lipoprotein cholesterol (HDL-C) in plasma is now established as an independent risk factor for coronary heart disease, but more data are needed on the relative risk-predictive powers of different HDL subclasses. For epidemiologic and clinical purposes, isolation of HDL from other lipoproteins and separation of its two major subclasses, HDL2 and HDL3, are performed most conveniently by precipitation. Although storage of plasma is commonly necessary, little information is available on the long-term stability of HDL subclasses at different temperatures. Therefore, we quantified HDL-C, HDL2-C, and HDL3-C by dual precipitation with heparin-MnCl2/15-kDa dextran sulfate (H-M/DS) in samples of EDTA-plasma from 93 healthy subjects, after storage for one to 433 days at -20 degrees C, at -70 degrees C, or in liquid nitrogen (-196 degrees C). Fourteen samples (15%) were stored for a year or longer. At -20 degrees C, HDL-C decreased by 4.8% per year and HDL3-C decreased by 6.9% per year (P = 0.002 for both variables) relative to results obtained with samples stored in liquid nitrogen; total cholesterol, HDL2-C, and triglyceride did not change significantly at this temperature. When stored at -70 degrees C, none of the lipids showed any change relative to results obtained with liquid nitrogen. Thus, long-term storage of EDTA-plasma at -20 degrees C is unsuitable for subsequent quantification of HDL-C and its subclasses by H-M/DS dual precipitation. Storage at -70 degrees C is preferable, and is as reliable as storage in liquid nitrogen.
Evaluation of the RheumaStrip ANA profile test: a rapid test strip procedure for simultaneously determining antibodies to autoantigens U1-ribonucleoprotein (U1-RNP), Sm, SS-A/Ro, SS-B/La, and to native DNA
Authors: Paxton H , Bendele T , O'Connor L , Haynes D C
Published: January 2020

The "LipoGen RheumaStrip ANA Profile" test method (LipoGen, Inc.) is a new assay format for autoantibody detection in which recombinant autoantigens are used. This enzyme immunoassay, in test-strip format, detects antibodies to autoantigens U1-ribonucleoprotein (U1-RNP), Sm, SS-A/Ro, SS-B/La, and to native DNA (nDNA). We evaluated 200 antinuclear antibody (ANA)-positive and 100 ANA-negative sera for the presence of antibodies to U1-RNP, Sm, SS-A/Ro, SS-B/La, and nDNA by the new test-strip procedure. These data correlated well with those obtained with either Ouchterlony double immunodiffusion for U1-RNP, Sm, SS-A/Ro, and SS-B/La or with Crithidia luciliae indirect immunofluorescence for anti-nDNA. Assay sensitivity and assay specificity of the ANA Profile method as compared with those of established procedures were respectively as follows: 89.8% and 98.8% for U1-RNP, 86.4% and 95.3% for Sm, 97.9% and 89.3% for SS-A/Ro, 98.3% and 86.3% for SS-B/La, and 97.5% and 93.1% for nDNA. Agreement between the ANA Profile test and these other test methodologies ranged from 88.7% for the SS-B/La test to 97.3% for the U1-RNP test. This new test procedure substantially decreases the time and effort required to perform these assays. Total hands-on time and overall assay time were decreased by 72% and 97%, respectively.
Two new two-step immunoassays for free thyroxin evaluated: solid-phase radioimmunoassay and time-resolved fluoroimmunoassay
Authors: Nuutila P , Koskinen P , Irjala K , Linko L , Kaihola H L , Eskola J U , Erkkola R , Seppälä P , Viikari J
Published: January 2020

We measured concentrations of free thyroxin (FT4) in serum by using two new two-step FT4 assays--a solid-phase two-step radioimmunoassay. Spectria, and a time-resolved fluoroimmunoassay. Delfia--and compared the results with those by a two-step FT4 assay (RIA-gnost), a one-step FT4 analog assay (Amerlex-M), and FT4 measured after equilibrium dialysis. The new FT4 assays classified 30 hypothyroid and 43 hyperthyroid patients (untreated) well. In 138 patients with nonthyroidal illness (NTI) and in late pregnancy (n = 36), fewer subnormal FT4 values were reported by Spectria (P less than 0.001), Delfia (P less than 0.001), and RIA-gnost (P less than 0.01) than by Amerlex-M. The results of the Spectria and Delfia methods correlated with the results of the dialysis method (r = 0.76) in NTI patients and pregnancy, and were in better agreement with the clinical state than was FT4 by Amerlex-M. The FT4 values by Amerlex-M, but not by other methods, correlated with albumin concentration. We conclude that these new two-step methods present good alternatives for FT4 analysis.
Do enzymatic analyses of serum triglycerides really need blanking for free glycerol?
Authors: Jessen R H , Dass C J , Eckfeldt J H
Published: January 2020

Distributions of concentrations of free glycerol in clinical plasma obtained for triglyceride assay were compiled to determine the frequency with which increased concentrations of free glycerol posed a potential problem for clinical interpretation of triglyceride results. Clinical histories were studied in patients with increased concentrations of free glycerol to ascertain possible reasons for the increase and to assess the relative clinical importance of glycerol-blank-corrected triglyceride results. Significant increases in free glycerol were very uncommon, usually occurring in patients receiving glycerol-containing hyperalimentation fluids, those receiving heparin (which causes both in vivo and in vitro increases in free glycerol), or those critically ill. Free glycerol was never increased significantly in a large outpatient population. Monitoring lipid metabolism in critically ill patients, or measuring true triglyceride concentrations in patients receiving glycerol-containing fluids, may represent rare exceptions for which glycerol-blank correction is necessary for accurate clinical diagnosis and management. We conclude that there is insufficient justification for the routine expenditure of extra time and reagents to correct most analytical enzymatic triglyceride methods for free glycerol.
Determination of Inorganic Nitrate in Serum and Urine by a Kinetic Cadmium-Reduction Method
Authors: Cortas Najwa K , Wakid Nabll W
Published: January 2020

Nitrate in serum and urine was assayed by a modification of the cadmium-reduction method; the nitrite produced was determined by diazotization of sulfanilamide and coupling to naphthylethylene diamine. After samples were deproteinized with Somogyi reagent, the nitrate was reduced by Cu-coated Cd in glycine buffer at pH 9.7 (2.5 to 3 g of Cd granules for a 4-mL reaction mixture). The reduction followed pseudo-first-order reaction kinetics, a convenient time interval for assay being 75 to 90 min. Maximum reduction (85%) occurred at about 2 h. Detection limits in urine or serum were 2 to 250 µmol/L. This method does not require the reaction to go to completion, does not require expensive reagents or equipment, and can assay several samples simultaneously. Repeated assays of two serum pools gave CVs of 9.0% and 4.7% for nitrate concentrations of 31.4 and 80.2 µmol/L, nitrate was 1704.0 ± 1294 (SD) µmol/L (n = 21) in untimed normal urine, 81.8 ± 50.1 µmol/L in serum of 38 renal dialysis patients, and 51.2 ± 26.4 µmol/L in serum of 38 controls.
Deamidation of glutamine by increased plasma gamma-glutamyltransferase is a source of rapid ammonia formation in blood and plasma specimens
Authors: da Fonseca-Wollheim F
Published: January 2020

Owing to increased enzymatic hydrolysis of glutamine, additional ammonia is formed in blood and plasma specimens with increased gamma-glutamyltransferase activity (gamma-GT, EC 2.3.2.2.). The close correlation between gamma-GT and glutaminase (EC 3.5.1.2) activities (r = 0.97) in plasma, the inhibition with 6-diazo-5-oxo-L-norleucin or borate plus serine, and the activation with maleate clearly show that gamma-GT itself is the glutamine-deamidating enzyme in plasma. Under pathological conditions, increased gamma-GT activity can increase the rate of ammonia formation in plasma more than 30-fold the mean values of healthy subjects. Increased in vitro formation of ammonia caused by increased gamma-GT activity is an important source of false-positive findings in ammonia determination. Because of the high prevalence of pathological gamma-GT activities in clinical populations, blood specimens for ammonia analysis should be preserved by addition of borate plus serine.
Optimized fluorometric determination of urinary delta-aminolevulinic acid by using pre-column derivatization, and identification of the derivative
Authors: Okayama A , Fujii S , Miura R
Published: January 2020

We previously reported the usefulness of a fluorometric method to determine urinary delta-aminolevulinic acid (ALA) concentrations by using post-column derivatization to monitor the effect of lead exposure. We have further improved the method by introducing pre-column derivatization by using reaction of ALA with acetylacetone and formaldehyde. Response of the hematopoietic system to lead exposure can now be easily detected at blood lead concentrations as low as 162 micrograms/L. The fluorescent ALA derivative, a new aromatic product, 2-methylideneamino-3,5-diacetyl-4,6-dimethylphenylpropionic acid, is separated on octadecyl silica column by high-performance liquid chromatography and the fluorescence intensity is detected with a fluorophotometer. Sample recoveries for 12 urine samples from workers exposed to lead and unexposed controls were 91.9-110.2%. The results obtained by the pre-column derivatization method agreed with those by the post-column derivatization method. The new method increases the sensitivity to a detection limit to 10 micrograms of delta-aminolevulinic acid per milliliter of urine and is simple enough to be used for routine monitoring of the biological effect of exposure to low concentrations of lead.
Impact of new technologies on health-care costs and on the nation's "health"
Authors: Massaro T A
Published: January 2020

By virtually all criteria, the American health-care system has the largest and most widely distributed technology base of any in the world. The impact of this emphasis on technology on the cost of care, the rate of health-care inflation, and the well-being of the population is reviewed from the perspective of the patient, the provider, and the public health analyst.
Integrating laboratory robots with analytical instruments--must it really be so difficult?
Authors: Kramer G W
Published: January 2020

Creating a reliable system from discrete laboratory instruments is often a task fraught with difficulties. While many modern analytical instruments are marvels of detection and data handling, attempts to create automated analytical systems incorporating such instruments are often frustrated by their human-oriented control structures and their egocentricity. The laboratory robot, while fully susceptible to these problems, extends such compatibility issues to the physical dimensions involving sample interchange, manipulation, and event timing. The workcell concept was conceived to describe the procedure and equipment necessary to carry out a single task during sample preparation. This notion can be extended to organize all operations in an automated system. Each workcell, no matter how complex its local repertoire of functions, must be minimally capable of accepting information (commands, data), returning information on demand (status, results), and being started, stopped, and reset by a higher level device. Even the system controller should have a mode where it can be directed by instructions from a higher level.
Preventing ascorbate interference in ion-chromatographic determinations of urinary oxalate: four methods compared
Authors: Petrarulo M , Marangella M , Bianco O , Marchesini A , Linari F
Published: January 2020

In an attempt to decrease ascorbate interference on the ion-chromatographic determination of urinary oxalate, we compared the effectiveness of four different methods for ascorbate elimination by analyzing a representative urine pool supplemented with successive ascorbate additions. Two of the methods--treatment with ferric ions or boric acid--have been described elsewhere; treatments with nitrites or ascorbate oxidase (EC 1.10.3.3) are investigated here as possible alternatives. Consideration of the main features, advantages, and drawbacks of the four procedures leads us to conclude that boric acid dilution is a good routine method and that pre-incubation with ascorbate oxidase reliably prevents ascorbate interference in assays of urinary oxalate.
Clinical evaluation of amperometric enzyme electrodes in continuous-flow analysis for glucose in undiluted whole blood
Authors: Gunasingham H , Tan C H , Aw T C
Published: January 2020

We have evaluated the carbon-paste enzyme/wall-jet electrode in continuous-flow analysis for glucose in undiluted whole blood. Responses of the electrode to protein-based and aqueous samples under wall-jet configuration are described. Imprecision in the flow-injection mode was less than 2% for glucose values in the usual analytical range (1-25 mmol/L). The dynamic range for glucose was from 0.03 to 45 mmol/L, with about 100% recovery of added substrate. The performance of the electrode (y) in flow-injection and steady-state modes was compared with a colorimetric method (x; Kodak Ektachem XR700), yielding linear-regression equations of y = 1.152x + 0.295 and y = 0.979x + 0.500, respectively. Among the anticoagulants, blood preservatives, and interfering substances investigated, only ascorbic acid gave a significant positive bias. The electrode exhibited good stability for analyses of undiluted whole-blood samples.
Effect of blood collection and processing on radioimmunoassay results for apolipoprotein B in plasma
Authors: Brown S A , Epps D F , Dunn J K , Sharrett A R , Patsch J R , Gotto A M , Patsch W
Published: January 2020

We studied the effects of different blood collection and processing procedures on quantification of apolipoprotein (apo) B by radioimmunoassay. High-density lipoprotein subfractions HDL3 and HDL2 and isolated apoA-I did not cross-react in the assay. Analytical recovery of apoB at different doses of very-low- and low-density lipoproteins were complete. Inter- and intra-assay coefficients of variation (CVs) averaged 7.4% and 6.0%, respectively. Blood from 20 subjects was collected into tubes containing EDTA alone or EDTA with antiproteolytic and antioxidant agents; one half of each plasma was separated immediately, half after 3 h at 4 degrees C. Regardless of the addition of protective agents or the time difference in separating plasma from other blood elements, freezing plasma at -70 degrees C decreased apoB content a similar amount, an average of 6.8%. This loss of apoB immunoreactivity was not related to apoB content in fresh plasma. Analysis of variance showed no differential effect on apoB content by the various additions to whole blood or plasma. No additional apoB content was lost in once-frozen aliquots of three human plasma pools during storage at -70 degrees C for up to 18 months. We conclude that concentrations of apoB in human plasma can be measured reliably after long-term storage, although the absolute value may decrease slightly as a result of freezing.
Medium-chain acyl-CoA dehydrogenase deficiency: a useful diagnosis five years after death
Authors: Bennett M J , Pollitt R J , Taitz L S , Variend S
Published: January 2020

We report a family in whom a fatal case of medium-chain acyl-CoA dehydrogenase (MCAD; EC 1.3.99.3) deficiency was diagnosed by enzymatic analysis of heart tissue that had been stored for five years. Three healthy siblings underwent subsequent investigation with the 3-phenylpropionic acid loading test. All siblings had been asymptomatic; however, one (age 2.5 years) excreted large amounts of 3-phenylpropionylglycine in response to the load and exhibited an organic aciduria consistent with the diagnosis of MCAD deficiency. The other two siblings did not demonstrate 3-phenylpropionylglycinuria after the loading test. This case underlines the importance of considering family history and using appropriate diagnostic tests in the recognition of hereditary metabolic disorders.
Multi-factor designs. IV. How multi-factor designs improve the estimate of total error by accounting for protocol-specific biases
Authors: Krouwer Jan S
Published: January 2020

Total error is often calculated as a combination of random error and fixed bias. However, the specific protocols used to estimate random error and fixed bias are themselves variable factors that can affect the estimate of total error. We refer to biases such as assay drift, sample-to-sample carryover, and reagent carryover as examples of fixed biases that are protocol-specific and distinguish them from other fixed biases. Failing to account for protocol-specific biases that are present will lead to incorrect estimates of total error when routine use of the assay involves a protocol different from that used to estimate total error. Multi-factor protocols are recommended to determine protocol-specific biases, which, if present, should be included in the estimate of total error.
Ion-chromatographic determination of L-tartrate in urine samples
Authors: Petrarulo Mlchele , Marangella Martino , Bianco Omalla , Linari Franco
Published: January 2020

We propose using ion chromatography to determine tartrate concentration in urine. A 100-microL sample of urine is diluted and injected into the chromatograph. Tartrate is eluted within 11.5 min as a distinct and well-resolved peak. The sensitivity of the standard procedure (signal-to-noise ratio, 3/1) is 30 mumol/L. The intra-run and interrun coefficients of variation are 2.5% and 4.1%, respectively. Mean analytical recovery of known amounts of added tartrate ranges between 94.2% and 104.0%. We investigated the specificity of the procedure by analyzing urine containing added dicarboxylic acids structurally related to tartrate. The reliability of the procedure makes it suitable for investigating tartrate metabolism, e.g., the potential role of tartrate as an inhibitor of crystallization in calcium nephrolithiasis.
Microtechnique for quantifying phenol in plasma by gas chromatography-mass spectrometry
Authors: Harrison L M , Morrison J E , Fennessey P V
Published: January 2020

Methods for detection and quantification of phenol have been developed primarily for use in environmental and industrial monitoring, given the widespread use of phenol as a disinfectant and antiseptic. Little information is available regarding concentrations of phenol in the blood of patients treated with phenol in regional nerve blocks (e.g., intrathecal) for temporary relief of pain or spasticity. We report a specific and sensitive method for quantifying phenol in plasma, using chemical derivatization and high-resolution capillary column gas chromatography in conjunction with mass spectrometry. The assay we describe was developed to monitor plasma concentrations of phenol in children given motor point nerve blocks with dilute phenol.
Role of vasopressin in clinical hypertension and congestive cardiac failure: interaction with the sympathetic nervous system
Authors: Gavras H
Published: January 2020

The pressor action of vasopressin (AVP) in humans was investigated with the specific anti-vasopressor V1 antagonist d(CH2)5-O(Me)-Tyr-AVP. A single 0.5-mg intravenous bolus of this agent inhibited the pressor effect of AVP by about 80%. Normally hydrated humans had no blood pressure response to this dose, but this agent did prevent the blood pressure rise in response to exogenous AVP given in doses up to 200 milli-units/kg. Patients with severe hypertension, especially that associated with end-stage renal disease, tended to respond with moderate increases in blood pressure and plasma AVP after sodium overload and had a modest blood pressure fall (10-20 mmHg) in response to a single intravenous bolus of the AVP antagonist. Patients with an impaired sympathetic nervous system had increased sensitivity to the pressor action of AVP, in keeping with knowledge derived from experimental studies. These data suggest an interaction between AVP and alpha-adrenergic function, whereby the latter tends to attenuate the pressor action of AVP although it facilitates the release of AVP in response to various stimuli. In patients with congestive heart failure, the direct pressor action of AVP appears to contribute to increased systemic vascular resistance in about 30% of cases, i.e., those with plasma AVP concentrations well above the normal range. In these subjects, circulating AVP concentrations correlated with a decrease in vascular resistance in response to the V1 antagonist.
Diabetic nephropathy: a disease causing and complicated by hypertension
Authors: Steffes M W , Mauer S M
Published: January 2020

In examining the pathophysiology underlying the development of hypertension in diabetes mellitus, it is important to draw clear distinctions between Type I and Type II diabetes. In patients with Type I diabetes, with a peak onset of disease early in the second decade of life, hypertension clearly represents the sequelae to the development of substantial renal lesions, especially in the glomerulus. Thus the prevalence of hypertension in those patients without substantial glomerular lesions approximates the incidence of hypertension in the general population (approximately 4%). In patients with Type II diabetes mellitus and onset generally later in adult life, an increase in blood pressure can often be demonstrated early after or even before diagnosis of the disease (most readily demonstrated in the Pima Indians). Furthermore, clear familial tendencies towards the development of nephropathic complications of diabetes can be shown. In patients with Type I disease, the fall in glomerular filtration rate parallels the fall in glomerular capillary surface available for filtration. This reduction in the peripheral glomerular capillary surface correlates well with the expansion of the mesangium, strongly implicating the mesangial expansion in the demise in renal function. For both Type I and Type II diabetes mellitus, the increase in albuminuria may reflect an opening of large pores in the glomerular basement membrane, thereby allowing serum proteins to cross into the filtration space.
Importance of creatinine analyses of urine when screening for abused drugs
Authors: Lafolie P , Beck O , Blennow G , Boréus L , Borg S , Elwin C E , Karlsson L , Odelius G , Hjemdahl P
Published: January 2020

We report here a simple method involving urine creatine measurements for testing authenticity and reducing false-negative results in urine testing for drugs of abuse. Urinary creatinine in consecutive patient samples (n = 176) ranged between 0.1 and 31.9 mmol/L (mean 9.8 +/- SD 6.2) and the osmolality in these urines ranged between 49 and 1183 mOsm/kg (mean 595 +/- SD 276). With other consecutive samples in which creatinine was (arbitrarily chosen) less than 4.3 mmol/L (n = 85), the correlation with osmolality was lower. In 10 randomly selected urine samples from different patients, all "clean" for all drugs of abuse in initial immunological drug testing with approved methodology (in which creatinine was less than 4.3 mmol/L and osmolality was less than 200 mOsm/kg), five patients turned out to be drug positive after a simple concentration by volume. In a formerly heavy smoker of cannabis, the excretion of cannabinoids and creatinine was monitored for 93 days. The substances showed very good correlation throughout this period (r = 0.93, P less than 0.001), whereas simple measurements of cannabinoid concentrations would have falsely indicated several relapses of cannabis abuse. Urine samples used in drug-abuse testing should be tested for creatinine; if creatinine is less than 4.0 mmol/L, negative results for drugs may not be valid.
Improvement of a direct spectrophotometric assay for routine determination of superoxide dismutase activity
Authors: Bolann B J , Ulvik R J
Published: January 2020

The growing interest in measuring superoxide dismutase (EC 1.15.1.1) in many diseases calls for useful routine assays. For this purpose, the direct spectrophotometric method of Marklund (J Biol Chem 1976;251:7504-7) was improved to offer an alternative to the imprecise, indirect assays currently used. The decay of O2.- (from KO2) at pH 9.5 was monitored as the decrease in delta A (delta A = A250nm-A360nm). Superoxide dismutase was determined from the pseudo-first-order rate constant of O2.- dismutation. The precision of the assay was improved by increasing the concentration of O2.- and expanding the interval for measurements of O2.- concentrations to 4-16 mumol/L. Other assay characteristics, including temperature, were also optimized. In hemolysate the assay had a within-day CV of 5.5-13% and a between-day CV of 4%. Mn-superoxide dismutase and some superoxide dismutase mimics are inhibited at alkaline pH. Therefore, the method is primarily recommended for Cu,Zn-superoxide dismutase.
Plasma Neopterin as an Adjunct to C-Reactive Protein in Assessment of Infection
Authors: Sheldon Joanna , Riches P G , Soni N , Jurges E , Gore M , Dadian G , Hobbs J R
Published: January 2020

C-reactive protein (CRP) concentrations are increased in plasma in people with inflammatory conditions and bacterial infections. Plasma neopterin concentrations are increased in people with bacterial septicemias, viral infections, and graft vs host disease. Plasma concentrations of CRP and neopterin were measured daily in 21 bone-marrow transplant (BMT) patients, 64 patients in intensive-care units (ICU), and 12 patients with squamous cell carcinoma of the head and neck (HN). In the BMT patients, plasma neopterin measurements in addition to CRP measurements allowed infectious episodes to be distinguished from graft vs host disease. In the ICU patients, increased concentrations of CRP were not specific for infection and the additional plasma neopterin measurements did not improve this specificity. In all three patient groups, the derivation of a neopterin/CRP ratio was of no clinical use. These three groups of patients showed patterns of CRP and neopterin concentrations characteristic of their underlying diseases, the BMT patients with the immunological activation of graft vs host disease showed predominantly increased concentrations of plasma neopterin, ICU patients with infectious and inflammatory conditions had increased concentrations of both CRP and neopterin in plasma, and the HN group with localized inflammation showed increased plasma concentrations of CRP without increases in neopterin.
Bile acids and conjugates identified in metabolic disorders by fast atom bombardment and tandem mass spectrometry
Authors: Libert Raymond , Hermans Dominique , Draye Jean-Pierre , Van Hoof Françols Van , Sokal Etienne , de Hoffmann Edmond
Published: January 2020

From a study of the collision-activated fragmentation of bile acids, a qualitative analytical method based on negative ion fast atom bombardment tandem mass spectrometry has been developed. The times for sample preparation and analyses are short. Both free and conjugated bile acids are detected as they occur in biological fluids, without derivatization. For identifying bile acids and conjugates, the method offers better specificity and sensitivity than does the fast atom bombardment mass spectrometric technique alone. Specific scan modes have been developed for the selective detection of taurine conjugates, Δ4-unsaturated taurine conjugates, Δ4-3-keto free acids and their glycine conjugates, free acids and glycine conjugates bearing a hydroxyl group at the C-12 position, sulfates of glycine and taurine conjugates, and a C29 dicarboxylic bile acid, specific for generalized peroxisomal disorders. Applications of this technique demonstrate its potential usefulness, principally in the diagnosis of several peroxisomal disorders.
New enzyme-linked immunosorbent assay for glycocalicin in plasma
Authors: Kunishima ShinjI , Hayashi Klyotaka , Kobayashi Sentaro , Naoe Tomokl , Ohno Ryuzo
Published: January 2020

A new sandwich-type enzyme-linked immunosorbent assay for quantifying glycocalicin, a proteolytic fragment of platelet membrane glycoprotein Ib, is described. The assay is based on the use of two monoclonal antibodies raised against glycoprotein Ib and involves the avidin-biotin technique. The detection limit is 7 micrograms/L and the range of glycocalicin determined in plasma is 0.01 to 1 mg/L. Assay time is 2 h. The intra-assay CV ranged from 3.6% to 5.2%, the interassay CV from 5.4% to 8.0%. Analytical recovery of purified glycocalicin added to a plasma pool averaged 96%. In 36 healthy subjects, the mean glycocalicin concentration in plasma was 0.36 (SD 0.07) mg/L (2.7 nmol/L). We conclude that this assay is suitable for measuring glycocalicin in plasma and is also more sensitive and precise than the previously published immunoassays based on competitive binding assay.
Complexes of creatine kinase and immunoglobulins in serum identified by a nonimmune binding method
Authors: Backer Egbert T , Hafkenscheid Jan C M , van Wermeskerken Robert K A
Published: January 2020

We have developed a method for identifying IgG-complexed creatine kinase (CK; EC 2.7.3.2) (IgG-CK) and IgA-complexed CK (IgA-CK) in serum. We used immobilized Protein G to bind IgG-CK and immobilized jacalin to bind IgA-CK, leaving noncomplexed CK in solution. The noncomplexed CK and total CK were measured kinetically. The results are reported as CK bound to immobilized Protein G and CK bound to immobilized jacalin. We validated the method by using sera determined immunochemically to contain IgG-CK, IgA-CK, mitochondrial CK (CKmt), and free CK-BB. We demonstrated concomitant binding of CK and approximately 99% of IgG, and of CK and approximately 87% of IgA. For CK bound to immobilized Protein G and to immobilized jacalin, intra- and interassay precisions ranged from 2.5% to 9.6%, and detection limits were less than 9 318 U/L in 40 sera containing IgG-CK, and CK bound to immobilized jacalin ranged from 10 to 59 U/L in eight sera containing IgA-CK. These ranges represent the activities of immunoglobulin-bound CK in the sera. In 13 sera containing CKmt and in eight sera containing free CK-BB, the binding of CK was less than 9 U/L. Evidently, this method is useful for identifying IgG-CK and IgA-CK in serum.
Plasma protein-bound sialic acid in patients with colorectal polyps of known histology
Authors: Shahangian Shahram , Fritsche Herbert A , Hughes John I , Foemmel Richard S , Katopodis Nonda
Published: January 2020

Protein-bound sialic acid (PBSA) was measured in serial plasma specimens from 62 healthy subjects, 48 patients with colorectal polyps, and 30 patients with colorectal adenocarcinomas. The mean plasma PBSA concentration in healthy smokers was significantly greater than that in healthy nonsmokers and healthy ex-smokers (P less than 0.0001). Villoglandular polyps were associated with higher plasma PBSA values than were the most benign hyperplastic polyps (P less than 0.025). Patients with the most neoplastic villoglandular and villous polyps had significantly greater (P less than 0.010-0.050) plasma PBSA values than healthy subjects. Polypectomy decreased the mean PBSA value significantly to the mean value for healthy subjects only for patients with villoglandular (P less than 0.010) or villous (P less than 0.050) polyps. Colorectal cancer patients had mean plasma PBSA concentrations significantly greater than those for the healthy subjects (P much less than 0.001) and the polyp patients (P much less than 0.001). Surgery significantly reduced (P less than 0.025) the mean PBSA value for the cancer patients to the mean PBSA value observed for the healthy subjects.
Simplified format for DNA probe-based tests
Authors: Bains William
Published: January 2020

The approach I describe to using DNA probes in diagnostic tests is simpler than most existing formats. DNA in a sample is labeled by chemical reaction with bisulfite and methylamine to generate a sulfonated derivative. The DNA need not be purified to do this. The labeled sample is then incubated with an unlabeled, purified probe DNA, which is immobilized to a solid support. The amount of label remaining on the solid support after washing is detected by a monoclonal antibody that recognizes modified cytosines. The intensity of the signal depends on the amount of target DNA in the sample. Detection limits depend on the amount of immobilized DNA and on the degree of physical entrapment of the labeled DNA in sample material, but can be as low as 5 pg. This format is well suited to automation for use with existing robotic enzyme immunoassay procedures.