bluuebunny/crossref_metadata_2025 huggingface dataset:
Abbott TDx, Dade Stratus, and Du Pont aca automated digoxin immunoassays compared with a reference radioimmunoassay method.
Authors: Clark D R , Inloes R L , Kalman S M , Sussman H H
Published: January 2020

Automated digoxin immunoassays with the Abbott TDx, Dade Stratus, and Du Pont aca were evaluated against an RIA similar to the Centers for Disease Control Candidate Reference Method. All three automated methods correlated poorly with the reference method. Particularly disconcerting were the falsely increased values (up to 0.6 micrograms/L) obtained by the Stratus for blank specimens. We discuss the inaccuracies of the results in terms of sample matrix effects, calibrator problems, lot-to-lot reagent variation, and our laboratory requirements. We strongly support the acceptance of the CDC Candidate Reference Method for digoxin and the establishment of a standardized protocol for determining the accuracy of digoxin measurements.
Immunoradiometric assay of thyrotropin in plasma: its value in predicting response to thyroliberin stimulation and assessing thyroid function in amiodarone-treated patients.
Authors: Wiersinga W M , Endert E , Trip M D , Verhaest-de Jong N
Published: January 2020

We measured thyrotropin in plasma by an ultrasensitive immunoradiometric assay (TSH-IRMA, "Sucrosep," Boots-Celltech), before and after thyroliberin (TRH) stimulation, in 71 patients with suspected thyroid-function disorders. Thirty-three were taking amiodarone; none was receiving (anti)thyroid drugs. The patients were divided into four groups, according to their TSH response to TRH (as measured previously by conventional TSH-RIA) and the concentrations of thyroxin (T4) and triiodothyronine (T3) in their plasma. Observed ranges of plasma TSH-IRMA (milli-int. units/L) before and after TRH were: euthyroid (n = 20), 0.2-3.0 and 1.7-15.5; subclinically hypothyroid (n = 14), 4.3-18.5 and 20-75; hyperthyroid (n = 17), less than 0.09 and less than 0.09-0.4; and subclinically hyperthyroid (n = 20), less than 0.09-1.1 and less than 0.09-2.6. Evidently TSH-IRMA results for a single sample completely distinguish hyperthyroidism from euthyroidism. However, TSH-IRMA values may also be undetectable in subclinical hyperthyroidism. The TSH response to TRH can be predicted from basal TSH-IRMA results less than 0.09 or greater than or equal to 0.8 milli-int. unit/L, intermediate values can be associated with either a normal TSH response (euthyroidism) or a decreased TSH response (subclinical hyperthyroidism only). We advocate TSH-IRMA as the first diagnostic test of thyroid function for amiodarone-treated patients.
Statistical analysis of the stability of the standard curve for some Syva EMIT assays.
Authors: Zvaigzne G V , Brogan D A , Bernstein L H
Published: January 2020

Derivation of standard curves for the EMIT therapeutic drug monitoring system involves several mathematical algorithms, all of which can be rewritten in the form of a linear equation y = mx + b. We examined the stability of the standard curve in terms of slope and y-intercept for three drug assays (procainamide, gentamicin, and carbamazepine) by generating calibration curves intermittently for periods as long as 90 days. Controls at three concentrations were assayed after each calibration to validate the standard curves. On the basis of 98% confidence intervals, the slopes of standard curves for procainamide, gentamicin, and carbamazepine were stable for 89, 80, and 57 days, respectively. Control values generated from standard-curve manipulations (adjustments to the y-intercept) indicated consistent accuracy and precision throughout the entire study, as compared with control values determined after each calibration. The increased utility of the standard curve and reagents suggests that full recalibration on a regular basis is not always necessary.
Radioimmunoassay for assessing exocrine pancreatic insufficiency, based on the differential enzymatic degradation of cobalamin-binding proteins.
Authors: Marcoullis G , Gueant J L , Nicolas J P
Published: January 2020

Pancreatic proteases degrade the protein moiety of the R protein-cobalamin complex but not the intrinsic factor-cobalamin complex. Accordingly, we used these two proteins as substrates in an in vitro enzymatic assay to assess pancreatic function by incubating basal jejunal fluids with a mixture of intrinsic factor and cyano[57Co]cobalamin coupled to R-type protein and then using immunoprecipitation to determine the distribution of isotopically labeled cobalamin bound to the two proteins. With normal jejunal fluids, 91.2 (SD 6.1)% and 4.5 (SD 5.5)% of cyano[57Co]cobalamin was precipitated with antisera to intrinsic factor and anti-R protein, respectively. In the patients' jejunal fluids, the cyano[57Co]cobalamin precipitated with the respective antisera was 5.3 (SD 10.0)% and 96 (SD 6.2)%. In patients with other gastrointestinal problems, the sequestration of cobalamin was indistinguishable from that observed with the normal fluids. The clearcut discrimination this radioimmunoassay provided between abnormal and normal samples was confirmed by parallel comparative chromatographic analysis.
Evaluation of a new dynamic viscometer for measuring the viscosity of whole blood and plasma.
Authors: Chandler W L , Schmer G
Published: January 2020

We evaluated a new type of dynamic viscometer, the Sonoclot Coagulation Analyzer, for use in measuring the viscosity of whole-blood and plasma. Such information can be useful in monitoring patients with hyperviscosity syndromes, e.g., from multiple myeloma. A vibrating Teflon or plastic probe continuously measures dynamic viscosity. The instrument can be calibrated to measure a range of viscosities from 0.69 to 23 cP (mN X s X m-2) or more. The coefficient of variation at 0.69 cP was 3-4% for measurements with the Teflon probe, 7-9% with the plastic probe. Viscosity measured at 37 degrees C for plasma and whole-blood samples from 20 normal patients was 1.22 (SD 0.05) cP and 3.63 (SD 0.52) cP, respectively. Dynamic viscosity measured in blood samples from a single source, with contrived hematocrits ranging from 0 to 89%, increased exponentially as a function of hematocrit, confirming previous studies. Overall, we found this instrument simple and quick to operate, producing accurate, precise viscosity measurements over at least a 40-fold range of viscosity.
Liquid-chromatographic determination of progesterone in serum, with spectrophotometric detection.
Authors: Laganà A , D'Ascenzo G , Marino A , Tarola A M
Published: January 2020

In this precise, accurate, and specific liquid-chromatographic procedure for determining progesterone in serum, the serum is diluted 10-fold with water/methanol (65/35 by vol), and the progesterone is extracted from the sample by passage through a column of graphitized carbon black (Carbopack B, Supelco). After washing the column, we elute the progesterone with chloroform/methanol (90/10 by vol), which is then evaporated. The progesterone is separated on a reversed-phase C18 column with a mobile phase of acetonitrile/water, (46/54 by vol) at a flow rate of 1.6 mL/min. The eluted compound is detected by absorbance at 242 nm. Analytical recoveries for progesterone varied from 96.0 to 97.8%. Within-day and day-to-day precision, determined by analyzing pooled serum, ranged from 3.4 to 6.4%, and 4.1 to 7.9%, respectively. The limit of detection was about 0.2 micrograms/L. Numerous drugs and steroids tested did not interfere. Results correlated (r = 0.997) well with those by radioimmunoassay.
Rapid determination of iron in urine, in the presence of deferoxamine, by inductively coupled plasma emission spectrometry.
Authors: Leflon P , Plaquet R
Published: January 2020

Using a spectrometer with an argon plasma source coupled to a high-frequency magnetic field, we developed a direct method for determining iron in urine of patients being treated with deferoxamine. The detection limit for iron was 75 nmol/L; added iron was satisfactorily recovered; and we observed no interference from deferoxamine at its most commonly used concentrations. Values for between-run and within-run precision (CV) was less than 5%. Correlation of results with those obtained with a colorimetric method involving bathophenanthroline was good (r = 0.96).
Mass-spectrometric determination of serum cortisol: comparison of data from two independent laboratories.
Authors: Gaskell S J , Sieckmann L
Published: January 2020

Isotope dilution and mass spectrometry were used in two independent laboratories to determine cortisol in 15 plasma and serum pools used in the British and German national schemes for the external quality assessment of routine assays. For the concentration range 240-700 nmol/L, differences between the data obtained by the two laboratories were generally less than 4% but were approximately 7% in two instances. The discrepancies are nevertheless small in comparison with the bias observed for many routine assays.
Evaluation of absorption and first- and second-derivative spectra for simultaneous quantification of bilirubin and hemoglobin.
Authors: Merrick M F , Pardue H L
Published: January 2020

We discuss the relative merits of absorption and first- and second-derivative spectra for the simultaneous quantification of bilirubin and hemoglobin, and evaluate single-, two-, and multiwavelength methods. Although both species can be quantified from single- or two-wavelength absorption data, lipids or other absorbing or light-scattering components introduce systematic errors that can be substantially decreased by using first- or second-derivative spectra. Multi-wavelength data-processing methods with derivative spectra permit quantification of components with overlapping spectra and decrease the random error usually associated with derivative methods. A typical least-squares equation for quantifying bilirubin in the presence of hemoglobin and bovine serum albumin from multi-wavelength second-derivative data is y(computed) = 0.999x(prepared) + 0.00 mg/L.
Accuracy and comparability of long-term measurements of cholesterol.
Authors: Hainline A , Karon J M , Winn C L , Gill J B
Published: January 2020

Laboratories of the Lipid Research Clinics Program (LRC) maintained the accuracy of their measurements of total cholesterol by using seven pooled serum calibrators supplied by the Centers for Disease Control (CDC). Over the 11-year life of the LRC, each calibrator was prepared in succession and a target value was assigned by the CDC reference method for cholesterol. The results of a special experiment in which six of the seven calibrators were analyzed simultaneously demonstrated that the target values were accurately assigned. Deviations of the target values from the experimental means ranged from zero to 1.7% of the original target value. The experiment revealed no evidence of drift in the bias of the reference method over the life of LRC and demonstrated the accuracy, consistency, and the comparability of the values assigned to the successive calibrator pools used by the LRC laboratories during more than eight years. It demonstrated the reliability of a reference method and the suitability of frozen serum pools for maintaining an accurate measurement base for serum cholesterol.
Lactate dehydrogenase isoenzyme-1/total ratio: accurate for determining the existence of myocardial infarction.
Authors: Adan J , Bernstein L H , Babb J
Published: January 2020

We have gradually revised our medical protocols for measuring creatine kinase MB isoenzyme (CK-MB) and lactate dehydrogenase isoenzyme-1 (LD-1) because of identifiable problems in the use of an interpretation of CK-MB isoenzyme associated with slowly evolving or small myocardial infarct, the use of thrombolytic therapy, or burn and trauma, each of which affects the rate of appearance and composition of isoenzymes present. Despite recent evidence of the efficacy of LD-1 isoenzyme measurement in the first 12 to 24 h of myocardial infarction, this test is not widely used because of overstated assumptions about the value of CK-MB. Here we studied the adequacy of the current isoenzyme assays by determining the value of CK-MB and LD-1 at optimum serum sampling times and establishing the contribution of individual and combined predictors to diagnostic efficiency. We conclude that the LD-1/total LD activity ratio in serum is superior to measurement of CK-MB or LD-1, or both, in the diagnosis of acute myocardial infarction. Moreover, this ratio is most valuable when interpretation of the result for CK-MB isoenzyme is equivocal in patients with small or evolving myocardial infarcts.
Changes in concentrations of C-reactive protein in serum after kidney or heart transplantation.
Authors: Van Lente F , Castellani W , Abbott L B
Published: January 2020

C-reactive protein (CRP) concentrations were serially determined in serum after kidney or heart transplantation. The initial postsurgical CRP response in these patients was compared with that of control patients undergoing related procedures but not subjected to immunosuppressive therapy. Immunosuppression clearly depressed the postsurgical CRP response in transplant recipients. The effect is greatest with the administration of cyclosporine. In addition, we found serial CRP determinations to be a sensitive indicator of renal but not cardiac allograft rejection. The specificity of CRP as such a predictor was affected by non-rejection-based inflammation. We conclude that serial determination of CRP, interpreted by the extent by which its concentration increases between sequential samples, may be a useful adjunct to biochemical monitoring of renal transplants, but a similar approach to monitoring heart transplants is not possible.
Distribution of paraoxon hydrolytic activity in the serum of patients after myocardial infarction.
Authors: McElveen J , Mackness M I , Colley C M , Peard T , Warner S , Walker C H
Published: January 2020

The activity of paraoxonase in serum was found to be bimodally distributed, both in a control group and in a group of patients who had suffered myocardial infarction. Activity in the myocardial infarct group was significantly lower than in the control group. Low paraoxonase activity in serum may provide an indication of susceptibility to the development of coronary heart disease.
Assessment of a time-resolved fluoroimmunoassay for thyrotropin in routine clinical practice.
Authors: Lawson N , Mike N , Wilson R , Pandov H
Published: January 2020

We assessed the use of a dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) system to measure thyrotropin (thyroid-stimulating hormone, TSH) in routine clinical practice. The assay is simple and precise, with intrabatch CV of less than 10% down to 0.1 milli-int. unit/L. When compared with free thyroxin, total thyroxin, and triiodothyronine measurements in 142 patients, the present assay most sensitively indicated hyperthyroidism and, in conjunction with free thyroxin, most sensitively indicated hypothyroidism. Free thyroxin was the most specific assay (lowest number of falsely increased or decreased results) in detecting thyroid disorders, with a specificity of 93.6% as compared with 85.1% for TSH, 81.9% for thyroxin, and 77.6% for triiodothyronine.
Concentration of free thyroxin in serum of a patient with euthyroid hyperthyroxinemia secondary to increased thyroxin-binding prealbumin: results by various methods compared.
Authors: Skiest D , Braverman L E , Emerson C H
Published: January 2020

We used various kits to measure free thyroxin (T4) in serum from a patient with the very rare syndrome of euthyroid hyperthyroxinemia secondary to increased thyroxin-binding prealbumin in serum. This patient's free T4 by equilibrium dialysis was 13 ng/L (normal 9-21), whereas the free-T4 index was 18.6 (normal 5.5-11.5). Using six different commercial methods, the last three listed being T4-analog methods, we measured the serum free T4 in this patient. The mean +/- SD (and normal range) free-T4 concentrations (ng/L) measured were: GammaCoat, Two-Step, 19.2 +/- 4.5 (6.9-26.9); Liquisol, 17.8 +/- 3.0 (12.4-20.8); Immo Phase, Two-Step 26.8 +/- 0.3 (12.4-21.2); GammaCoat, Single-Step, 19.7 +/- 5.7 (10.3-21.0); Immo Phase, Single-Step, 27.7 +/- 0.9 (8.6-25.0); and Amerlex, 14.1 +/- 0.6 (5.3-14.1). In four patients with familial dysalbuminemic hyperthyroidism, in whom the serum T4 by equilibrium dialysis was normal, all three T4-analog methods gave results far exceeding normal (greater than 50 ng/L).
Creatine kinase variant type I in children with anoxic insult.
Authors: Ludvigsen C W , Muus C , Meyer I , Haven M
Published: January 2020

We evaluated 31 consecutive patients, including 11 children, with creatine kinase variants (CKV) in our laboratory during a year. All had a clinical history of central hypotonia with myocardial damage resulting in severe central hypoxia. Seven of the 11 were neonates and had Apgar scores of 2.8 (SD 2.3) at 1 min and 4.8 (SD 2.4) at 5 min, which reflected their severe birth hypoxia. For the seven neonates, the mean value for total serum creatine kinase (EC 2.7.3.2; CK) was 773 (SD 553) U/L. The mean percentage CKV was 20.7% (SD 12.5%). The other four children were being evaluated for failure to thrive; all had birth asphyxia with residual cerebral palsy and seizure activity. These older children had a lower percentage of CKV (7.3%, SD 1.01%) than did the neonates, but the total CK (725, SD 1335 U/L) was not significantly different. In four neonates there was a three- to 20-day delay in the appearance of CK variant, which followed a marked increase in total CK activity. Tissue necrosis is apparently an important factor in the pathogenesis of Type I CK variant.
Four monoclonal immunoglobulins in a patient with chronic lymphocytic leukemia.
Authors: Tienhaara A , Irjala K , Rajamäki A , Pulkki K
Published: January 2020

We report here the case of a 73-year-old woman with chronic lymphocytic leukemia. Two years after the diagnosis, electrophoresis of her serum showed two monoclonal fractions, but our modified immunofixation procedure revealed four monoclonal immunoglobulins in five fractions: two IgG lambda fractions, one IgG kappa fraction, one IgA kappa fraction, and one IgG kappa fraction. This is an exceptionally high number of monoclonal immunoglobulins in a single patient. In the course of her disease the patient did not show any clinical, radiological, or laboratory signs of multiple myeloma or macroglobulinemia. The different monoclonal immunoglobulins were considered to be one expression of her B-lymphocytic malignancy.
Luminometric assays of seven acute-phase proteins in minimal volumes of serum, plasma, sputum, and bronchioalveolar lavage.
Authors: Braun J , Schultek T , Tegtmeier K F , Florenz A , Rohde C , Wood W G
Published: January 2020

We describe immunoluminometric assays for seven acute-phase proteins, which can be determined in minimal volumes of plasma, serum, sputum, and bronchioalveolar lavage. The theoretical volume of serum or plasma required to measure all seven analytes in duplicate is 130 nL, although in practice the smallest volume of sample was enough to fill a hematocrit tube (about 25 microL of blood), collected from neonates by the heel-prick method. The assays could be performed with 10 microL of sputum or with 100 microL of bronchioalveolar lavage. We measured alpha 1-antitrypsin, alpha 2-macroglobulin, alpha 1-acid glycoprotein, thyroxin-binding prealbumin, C-reactive protein, and total and secretory immunoglobulin A. The assays are rapid enough for all results to be returned to the ward on the same day and are suitable for monitoring neonatal sepsis. All coefficients of variation, derived from compound precision profiles, were less than 7% for clinically relevant analyte concentrations. Correlation with commercially available nephelometric assays was good.
Colorimetric determination of carboxypeptidase A activity in serum.
Authors: Saruta H , Ashihara Y , Sugiyama M , Roth M , Miyagawa E , Kido Y , Kasahara Y
Published: January 2020

This simple, reproducible colorimetric method for determining the activity of carboxypeptidase A (EC 3.4.17.1) is based on measuring the absorbance at 505 nm of a quinoneimine dye produced from the action of this enzyme on the new substrate p-hydroxybenzoyl-glycyl-L-phenylalanine. The enzyme acts on the substrate to produce p-hydroxybenzoyl-glycine and L-phenylalanine. The former is then hydrolyzed by hippuricase (EC 3.5.1.14) to produce p-hydroxybenzoic acid and glycine. Finally, oxidative coupling of p-hydroxybenzoic acid with 4-aminoantipyrine by sodium periodate forms a quinoneimine dye. The Km for the reaction with this substrate is 3.6 mmol/L; the optimum pH is 7.8. Our within-run and between-run CVs are 4.3% and 6.6%, respectively. The activity of carboxypeptidase A in serum correlates well with that of lipase (r = 0.96) and immunoreactive elastase-1 (r = 0.76).
Turbidimetric assay of IgG with use of single monoclonal antibodies.
Authors: Maynard Y , Scott M G , Nahm M H , Ladenson J H
Published: January 2020

We describe a turbidimetric assay for quantifying total immunoglobulin G (IgG) in serum with use of a single monoclonal antibody. The reaction, monitored by a centrifugal analyzer, is technically simple, rapid, and precise. Buffer of low ionic strength and polyethylene glycol are required for formation of detectable antibody-antigen complexes. We measured IgG concentrations in 49 polyclonal sera (Group 1) and 84 sera containing monoclonal IgG (Group 2) in assays in which we used either of two anti-IgG monoclonal antibodies (HG6 or HG8). Results compared well with those obtained with a nephelometric assay involving polyclonal antiserum, except for sera from four persons of Group 2 whose immunoglobulins were not detected by antibody HG6. HG6 bound IgG from these four sera in a solid-phase binding assay. HG6 and HG8 recognize epitopes on the Fab and Fc regions of IgG, respectively, and they do not compete for binding to the whole molecule. However, use of the two monoclonal antibodies combined failed to improve the sensitivity or range of the assay. We conclude that light-scattering assays of IgG can be validly performed with a single monoclonal antibody.
Radioimmunoassay of laminin in serum and its application to cancer patients.
Authors: Brocks D G , Strecker H , Neubauer H P , Timpl R
Published: January 2020

In this sensitive radioimmunoassay for laminin fragment P1 (purified from pepsin extracts of human placenta), monovalent antibody fragments obtained from rabbit antisera against the laminin component are used. The inhibition assay showed a low intra- and interassay variability, and the inhibition curves for various serum samples had parallel slopes. Molecular-sieve chromatography demonstrated heterogeneity of the laminin antigen in serum. For quantification we defined arbitrary units based on the amount of antigenic material present in normal human serum. Sera from 361 tumor patients showed increased values in about half of the cases. Correlation with increased concentration of carcinoembryonic antigen was poor (r = 0.259). The assay may be useful for diseases involving basement-membrane metabolism.
Differences between young and elderly subjects in seasonal and circadian variations of total plasma proteins and blood volume as reflected by hemoglobin, hematocrit, and erythrocyte counts.
Authors: Touitou Y , Touitou C , Bogdan A , Reinberg A , Auzeby A , Beck H , Guillet P
Published: January 2020

Circadian and seasonal rhythms in total plasma proteins were documented in healthy young men (around 24 years old), and in elderly subjects (both sexes), including senile-dementia patients in their eighties. The concentration of plasma proteins within a given group changed predictably (7-13%), depending on the hour of sampling and the season. Concentrations decreased noticeably around 04:00 h, then peaked around 08:00 h (shortly after waking). The 24-h mean concentrations of total plasma proteins were lower in the elderly groups than in the young men. But the seasonal variations of the 24-h mean values were strikingly larger in the elderly groups (7-8 g/L) than in the young men (2-5 g/L). Moreover, the circadian profiles of plasma proteins differed from the profiles of hematocrit, hemoglobin, and erythrocyte counts. Evidently, circadian variations of blood volume may not be the only element accounting for the variations of plasma protein concentrations. We suggest that the rhythms in plasma protein concentrations be taken into account when reference values are set. Circadian and seasonal variations in plasma proteins may also significantly affect the transport and binding of drugs, especially in the aged.
Activities of superoxide dismutase and glutathione peroxidase in schizophrenic and manic-depressive patients.
Authors: Abdalla D S , Monteiro H P , Oliveira J A , Bechara E J
Published: January 2020

Activities of superoxide dismutase (EC 1.15.1.1) and glutathione peroxidase (EC 1.11.1.9) in erythrocytes were evaluated in 50 schizophrenic and 20 manic-depressive patients, who were or were not being treated with different neuroleptic drugs, and results were compared with those for 58 normal individuals. Neuroleptic-treated and untreated schizophrenic patients showed similar activities of superoxide dismutase, about 60% higher than those found in normal individuals (p less than 0.001). In manic-depressive patients treated with either lithium (n = 8) or lithium plus neuroleptic drugs (n = 12), superoxide dismutase activities were increased by about 40% over those of normal subjects (p less than 0.001). Significantly abnormal activities of glutathione peroxidase were found only in the sub-group of schizophrenic women. These results are interpreted in terms of active oxygen species involvement in the psychiatric manifestations.
Evaluation of the dual-precipitation method for determination of cholesterol in high-density lipoprotein subfractions HDL2 and HDL3 in serum.
Authors: Demacker P N , Hak-Lemmers H L , Hijmans A G , Baadenhuysen H
Published: January 2020

We compared the dual-precipitation method for measurement of cholesterol in high-density lipoprotein subfractions HDL2 and HDL3 (Gidez et al., J Lipid Res 1982;23:1206-33) with density-gradient ultracentrifugation in a swinging-bucket rotor (Demacker et al., Clin Chem 1983;29:656-63). The concentration of dextran sulfate 15,000 (DS) needed for optimal accuracy of the HDL2-chol and HDL3-chol values was established empirically. At a DS concentration of 0.87 g/L, the values for HDL2-chol as well as for HDL3-chol in 88 sera did not differ significantly from those obtained by ultracentrifugation. The precision of the method was satisfactory and was related to the concentration. Nevertheless, the dual-precipitation method lacks specificity inasmuch as it produces no fractions that contain only one HDL subfraction. HDL2 and HDL3 each contained an equivalent amount of cholesterol from the other. At increasing DS concentrations, some radiolabeled HDL3 appeared to have precipitated prior to complete precipitation of HDL2. This lack of specificity can be tolerated in large-scale epidemiological studies for screening, but not in small-scale intervention studies or in assay of clinical samples, where better accuracy is needed and ultracentrifugation is preferred.
Homogeneous apoenzyme reactivation immunoassay for thyroxin-binding globulin in serum.
Authors: Schroeder H R , Johnson P K , Dean C L , Morris D L , Smith D , Refetoff S
Published: January 2020

In this automated apoenzyme reactivation immunoassay system (Ames Optimate) for thyroxin-binding globulin (TBG), the sample and N6-aminohexylflavin adenine dinucleotide-labeled TBG react sequentially with antiserum. Then apoglucose oxidase is added to combine with the free fraction and generate glucose oxidase activity, which is measured colorimetrically. The assay requires 100 microL of sample and covers the clinically significant range for TBG (less than 2.5 to 55 mg/L). The first result is obtained in 16 min; assay of 29 samples and their blanks is completed in less than 1 h. The lower limit of detection is about 2.5 mg/L. Between-assay CVs (n = 9) were less than 9%, within-assay CVs (n = 5) were less than 6%, and analytical recovery of TBG was 103-112%. Reagents are stable at 4 degrees C for at least five months. Results by this method for serum TBG (y) compared well with those determined by radioimmunoassay (x): y = 1.029x--0.352 (r = 0.990, n = 49, Syx = 1.165 mg/L). In addition, with 39 other sera the ratio of total thyroxin (by RIA) to TBG compared well with free thyroxin measured by equilibrium dialysis (r = 0.930) and the free thyroxin index (r = 0.970).
Urinary serotonin in the diagnosis of carcinoid tumors.
Authors: Feldman J M
Published: January 2020

To determine whether measurement of serotonin in urine would give useful complementary information to the usual measurement of 5-hydroxyindoleacetic acid (5-HIAA) in urine and platelet serotonin in platelets, I measured these analytes in 75 consecutive patients with carcinoid tumors, and found that 75% had above-normal urinary 5-HIAA excretion, 64% had above-normal serotonin excretion, and 64% had above-normal platelet serotonin concentration. Six patients had increased urinary serotonin, but 5-HIAA excretion and platelet serotonin concentration were normal. Only two of a further 50 patients with solid noncarcinoid tumors--and none of 55 patients with flushing or diarrhea, who did not prove to have a carcinoid tumor--had increased urinary serotonin. Ingestion of four bananas (a food rich in serotonin) increased urinary 5-HIAA but not urinary serotonin excretion of seven normal subjects. Evidently, measurement of urinary serotonin excretion is helpful in the evaluation of patients with suspected carcinoid tumors.
Methotrexate interferes with determinations of conjugated bilirubin with the Kodak Ektachem 400.
Authors: Swanson S , Mifflin T E , Boyd J C
Published: January 2020

Immediately after intravenous infusion of a high dose (concentration in serum greater than 1000 mumol/L) of methotrexate, the apparent conjugated bilirubin (Bc) concentrations in serum of two osteosarcoma patients, as measured by the Kodak Ektachem 400 analyzer, were greater than the corresponding total bilirubin concentrations, but decreased as the concentrations of methotrexate in serum decreased. In an interference study we found that methotrexate added to sera containing a wide range of basal Bc concentrations increased the measured Bc concentration in a linear and dose-related fashion. Methotrexate also interfered negatively with measurements of unconjugated bilirubin (Bu). The source of the interference appears to be an overlap in the absorption spectrum of methotrexate with Bc and Bu at 400 nm.
Increased excretion of histidyl-L-proline diketopiperazine by infants receiving Pregestimil and Nutramigen formulas.
Authors: Roesel R A , Blankenship P R , Mobley E B , Coryell M E
Published: January 2020

Histidyl-L-proline diketopiperazine is excreted in increased amounts by infants receiving Nutramigen or Pregestimil. When these formulas are discontinued, its excretion becomes undetectable. The compound was isolated from Nutramigen and Pregestimil, as well as from the urine of the infants receiving these formulas, and was identified by comparison with authentic histidyl-L-proline diketopiperazine standard in various chromatographic and electrophoretic systems. A neuropeptide widely distributed in the brain and gut and having a variety of biological functions, histidyl-L-proline diketopiperazine may have as-yet-undetermined effects on infants who are receiving these formulas.
Use of Proton Nuclear Magnetic Resonance Spectroscopy in Detection and Study of Organic Acidurias
Authors: lles R A , Hind A J , Chalmers R A
Published: January 2020

Vol. 31, p 1797, column 2: The first paragraph under the heading Methylmalonic Aciduria should read: The spectrum (Figure 4) shows two large methylmalonate resonances ascribable to the CH3 group split by the adjacent CH into a doublet and the CH proton split in turn by the same CH3 group to give a quartet. All five patients with methylmalonic aciduria so far investigated show as the major signal the characteristic presence of large amounts of methylmalonate in their urine regardless of their clinical status, with some 3-hydroxypropionate also being present. Signals due to ketoaciduria were also evident in some samples.

p 2014: In line seven of column one, the interval should read 16-53 µmol/L.

Vol. 32, p 35: In the last two lines of last full paragraph, "70 °C" should read "-70 °C" and "20 °C" should read "-20 °C."

p 175: In Table 1, "0.20-0.96" should read "0.2-3.96."

p 179: In Figure 2, transpose A with C and B with D.

p 223: The Figure to the right should have accompanied the Letter by Brugués and Sastre.

p 521: Ref. 15 in the paper by Helenius and Tikanoja was omitted: Matsubara G, Kudo K, Kawashita T, Takamura K. Spectrophotometric determination of hydrogen peroxide with titanium 2-(5-bromopyridyl)azo-5-(N-propyl-N-sulfopropylamino)phenol reagent and its application to the determination of serum glucose using glucose oxidase. Anal Chem 1985;57:1107-9.

p 536: The second author is Lothar Siekmann.

See image in the PDF file.
Minimizing interlaboratory variation in routine assays of serum cholesterol through the use of serum calibrators.
Authors: Boerma G J , Jansen A P , Jansen R T , Leijnse B , van Strik R
Published: January 2020

A cholesterol standardization program was developed in The Netherlands for clinical laboratories that use their analytical results as indicators of cardiovascular risk. Participants with sufficient precision but inaccurate results are encouraged to use serum-based calibrators as a means to decrease bias. A regional pilot survey and thereafter a national one were carried out in 31 and 138 laboratories, respectively, to investigate whether use of the serum-calibration procedure could improve routinely performed cholesterol measurements. To participants in our national quality-control surveys were mailed three calibrators (pooled human serum) and five human-serum controls, for analysis of cholesterol on four different days. Reference method values had been assigned to the calibrators by the Netherlands Reference Laboratory, applying the U.S. Centers for Disease Control modification of the Abell-Kendall procedure. Using the calibration curves based on results for the serum calibrators decreased the between-laboratory variation (SD) by at least 50%, with improved accuracy for non-enzymatic methods. The initial within-laboratory precision was generally good, and improvements in it were small. To our knowledge, standardization results involving so many routine hospital laboratory procedures have not been previously reported.
Results of routine determination of clinically significant hemoglobin derivatives by multicomponent analysis.
Authors: Zwart A , van Kampen E J , Zijlstra W G
Published: January 2020

Our recently developed multiwavelength method for multi-component analysis of hemoglobin (Hb) derivatives (Clin Chem 1984;30:373-379) was adapted for routine use in the clinical chemical laboratory. The method was applied in 4066 determinations on blood specimens from patients awaiting major surgery (n = 3863) or visiting the outpatient department for pulmonary disease (n = 203). Mean total hemoglobin concentration was 141 (SD 14) g/L. The proportion of HbCO was slightly to moderately increased (1.5-10.0%) in 36.5% of all patients; in a few cases it was as high as 15%. Mean methemoglobin was 0.4% (SD 0.2%) in the surgical patients, but 1.5% (SD 0.8%) in the patients with pulmonary disease. In some patients of the latter group the proportion of methemoglobin amounted to 5%. Sulfhemoglobin was found less than 0.4% in all specimens. Interference by paraproteins and by increased concentrations of bilirubin and lipids in plasma was easily detected by means of the performance checks provided by the spectrophotometer (an HP 8451 UV/Vis). The method is equally suitable for measuring blood samples containing fetal hemoglobin.
Assays of serum lipase: analytical and clinical considerations.
Authors: Lott J A , Patel S T , Sawhney A K , Kazmierczak S C , Love J E
Published: January 2020

We evaluated three commercially available methods for determining lipase (EC 3.1.1.3) in serum--the Du Pont aca, Boehringer Mannheim Diagnostics (BMD), and Kodak Ektachem (EK) procedures--for their analytical properties and diagnostic efficiencies. Titrimetry was used as the comparative method. The BMD and EK methods showed better agreement with the titrimetric method, owing to the presence of the necessary cofactor, colipase, in their reagents. Colipase also increased the analytical sensitivity of the BMD and EK procedures as compared with the aca method. Determinations of serum lipase, by all methods, had a clinical sensitivity in excess of 80% for acute pancreatitis; the specificity of the lipase test was about 60%, or twice that of serum amylase. Serum lipase determinations with the current, simpler technology are superior to total amylase in the diagnosis of patients with acute pancreatitis. When a colipase-supplemented method is used, a serum lipase value greater than 10-fold the upper reference limit appears to be pathognomonic for acute pancreatitis or inflammation of organs close to the pancreas.
Calculating unknown concentrations from nonlinear standard curves.
Authors: Cverna F , Hamlin C R
Published: January 2020

We describe an algorithm and program for calculating unknown concentration values from nonlinear standard data. The program was developed as an alternative to current data-handling techniques used for therapeutic drug enzyme immunoassay (EMIT) systems. The shape of the standard curve for a given analyte is required to be stable through the lifetime of a reagent lot. The relationship between the net change in milliabsorbance and the natural log of standard concentration is linearized once for each lot of reagents. For each subsequent time the assay is performed, one corrects the individual standard points by using the linearized relationship. Unknown concentrations are then calculated by using quadratic Lagrangian interpolation. The algorithm is faster and simpler than curve-fitting by nonlinear least squares, gives comparable results for unknowns, and rejects fewer assays for poor curve fit.
Nonenzymatic glycation of human platelet membrane proteins in vitro and in vivo.
Authors: Sampietro T , Lenzi S , Cecchetti P , Giampietro O , Cruschelli L , Navalesi R
Published: January 2020

Human platelet membrane proteins (PMP), incubated in vitro in the presence of various concentrations of glucose, undergo nonenzymatic glycation, as evidenced by incorporation of [3-3H]glucose radioactivity into the acid-precipitable fraction. The time course of the reaction is linear for the first hours, and the rate of glycation depends on the glucose concentration in the medium: at a glucose concentration of 80 mmol/L, up to 60 nmol of glucose is bound per milligram of PMP. The ketoaminic nature of the glucose/protein linkages was demonstrated by the finding of 5-hydroxymethylfurfuraldehyde by liquid-chromatographic analysis of acid hydrolysates of PMP. We analyzed PMP from 13 subjects with type I poorly controlled diabetes and from 10 nondiabetics. Nonenzymatic glycation, evaluated as nanomoles of the aldehyde per milligram of protein, was much greater in diabetic patients than in nondiabetics: 1.58 +/- 0.70 vs 0.37 +/- 0.18 (mean +/- SD).
Assessing diagnostic tests once an optimal cutoff point has been selected.
Authors: Linnet K , Brandt E
Published: January 2020

The specificity and sensitivity of a quantitative diagnostic test depends on the chosen cutoff point. The common practice of selecting a cutoff point that maximizes the specificity plus the sensitivity, as judged from the observed test results, is studied here by simulation. Test performance is on average assessed too optimistically by this procedure--a phenomenon of importance when sample sizes are small. For example, the average positive bias is up to 15% of the test performance for sample sizes of 25. Furthermore, binomial calculated standard errors of specificity and sensitivity estimates are incorrect. A Monte Carlo statistical method--the "bootstrap procedure"--is applied to correct for bias and to estimate standard errors, including the standard error of the optimal cutoff point. Independent and paired comparisons of two diagnostic tests are also considered when optimal cutoff points have been selected. For this purpose, binomial statistical tests behave satisfactorily. Examples of power functions are presented.
Sampling and analysis techniques for monitoring serum for trace elements.
Authors: Ericson S P , McHalsky M L , Rabinow B E , Kronholm K G , Arceo C S , Weltzer J A , Ayd S W
Published: January 2020

We describe techniques for controlling contamination in the sampling and analysis of human serum for trace metals. The relatively simple procedures do not require clean-room conditions. The atomic absorption and atomic emission methods used have been applied in studying zinc, copper, chromium, manganese, molybdenum, selenium, and aluminum concentrations. Values obtained for a group of 16 normal subjects agree with the most reliable values reported in the literature, obtained by much more elaborate techniques. All of these metals can be measured in 3 to 4 mL of serum. The methods may prove especially useful in monitoring concentrations of essential trace elements in blood of patients being maintained on total parenteral nutrition.
Cyanocobalamin absorption in the elderly: results for healthy subjects and for subjects with low serum cobalamin concentration.
Authors: Nilsson-Ehle H , Jagenburg R , Landahl S , Lindstedt G , Swolin B , Westin J
Published: January 2020

We examined the intestinal absorption of cyano[57Co]cobalamin from a non-protein-bound test dose given to 38 subjects from a population of elderly. The subjects were 76 years old and were apparently free from conditions known to affect cyanocobalamin absorption. Their gastric mucosal function was normal, as judged from determinations of serum gastrin and pepsinogen I. The urinary excretion of radioactivity during the first 24 h was 24(SD 7)%, range 8.6 to 45.2%, corresponding to a health-associated reference interval of 10 to 38%. The results indicate that cyanocobalamin absorption does not decline during normal aging. Duplicate studies were performed in another 20 subjects (70-81 years old) from the same population study; these subjects had a serum cobalamin concentration less than 130 pmol/L. The imprecision (CV) was 23%.
A competitive immunoenzymometric assay for albumin in urine.
Authors: Townsend J C
Published: January 2020

I describe a competitive immunoenzymometric assay for urinary albumin, with use of an immobilized albumin-thyroglobulin conjugate and an affinity-purified antibody. The assay is rapid, easy to perform, has a range of 0.5 to 78 mg/L, and is ideally suited for screening purposes. Higher concentrations may be assayed by further dilution of the urine sample. Results compare favorably with those of a commercially available radioimmunoassay kit.
An optimized method for measuring cyclosporin A with 125I-labeled cyclosporin.
Authors: Felder R A , Mifflin T E , Bastani B
Published: January 2020

We evaluated the use of the new iodinated ligand for the in vitro measurement of cyclosporin A by radioimmunoassay (RIA). Substitution of the iodinated cyclosporin (125I-CyA) for the corresponding tritium-labeled analog (3H-CyA) considerably simplifies and accelerates the currently available RIA, and improves its precision. Analysis of the respective dose-response curves showed that the 50% B0 value was lower for the 125I-CyA assay than for the 3H-CyA assay (37 vs 77 micrograms/L). Use of whole-blood specimens minimized interferences from temperature and hematocrit. We conclude that the use of 125I-CyA in a commercially available RIA for whole-blood specimens is accessible to most laboratories and provides rapid, reproducible data for management of transplant patients.
Uniform chromatographic conditions for quantifying urinary catecholamines, metanephrines, vanillylmandelic acid, 5-hydroxyindoleacetic acid, by liquid chromatography, with electrochemical detection.
Authors: Parker N C , Levtzow C B , Wright P W , Woodard L L , Chapman J F
Published: January 2020

Uniform liquid-chromatographic conditions were developed such that we could quantify norepinephrine, epinephrine, normetanephrine, metanephrine, vanillylmandelic acid, and 5-hydroxyindoleacetic acid in urine by using a single mobile phase of monochloroacetic acid and citric acid, 0.1 mol/L each. All compounds were separated on a C18 column and detected electrochemically at a potential of +0.800 V. Optimization of these uniform chromatographic conditions significantly shortens the changeover time required from one assay to another, resulting in a substantial savings of time and cost to the laboratory.
Emergency screening for ethylene glycol in serum.
Authors: Ryder K W , Glick M R , Jackson S A
Published: January 2020

We have exploited the "interference" of ethylene glycol in the Du Pont aca triglyceride method to develop a convenient and rapid screening method for detecting ethylene glycol in serum. Pretreatment of patient's serum with lipase, glycerol kinase, and other cofactors usually added for triglyceride analysis removes triglycerides and glycerol, but not ethylene glycol, from the sample. The aca triglyceride method may then be used to estimate the ethylene glycol concentration in serum.
Catalytic concentrations of amylase isoenzymes: an assay with wheat-germ inhibitor and 4-nitrophenylmaltopentaoside plus 4-nitrophenylmaltohexaoside as substrate.
Authors: Jiménez A , Arenas J , Santos I , Martínez A
Published: January 2020

We coupled a kinetic procedure to a selective inhibiting method for determining amylase isoenzymes in biological samples, using 4-nitrophenylmaltopentaoside plus 4-nitrophenylmaltohexaoside as substrate and a wheat-germ selective inhibitor with the Gilford S-III spectrophotometer. On plotting remaining amylase activities/total amylase activities (R/T) vs pancreatic amylase activities/salivary amylase activities (P/S) ratios, we found the curve to be linear for P/S ratios from 0.2 to 5. The inhibition rate of amylase inhibitor was constant in solutions having total amylase activities between 20 and (at least) 900 U/L. CVs were 3.1 to 7.1% for pancreatic amylase and 2.0 to 12.9% for salivary amylase in serum. Correlation with the Phadebas method was excellent (r = 0.99) for both pancreatic and salivary amylase. We also automated this procedure in an Hitachi 705 analyzer and correlated the results (r = 0.99) with those by our manual method.
A kinetic colorimetric assay of gamma-glutamyltransferase.
Authors: Fossati P , Melzi d'Eril G V , Tarenghi G , Prencipe L , Berti G
Published: January 2020

We have explored a kinetic colorimetric method for measuring gamma-glutamyltransferase (EC 2.3.2.2) activity in serum, using L-gamma-glutamyl-3,5-dibromo-4-hydroxyanilide and glycylglycine as donor and acceptor substrates. The released product, 3,5-dibromo-4-hydroxyaniline, reacts with 2,5-dimethylphenol to produce a blue quinone monoimine in the presence of ascorbate oxidase (EC 1.10.3.3). This dye has peak absorption at 610 nm, whereas the donor substrate shows negligible absorption throughout the visible spectrum. The reaction can be run with all the reagents in a single working solution with serum as starter, or with the substrate solution as starting reagent. The sample/reagent volume ratio is 1:24. Adaptation of the method to several automated instruments gave good precision in all cases. Comparison with a method in which L-gamma-glutamyl-3-carboxy-4-nitroanilide is the donor substrate showed good correlation of results (r greater than or equal to 0.987). The dynamic range of the method exceeds the upper limits of the reference intervals for men (9-33 U/L) and women (8-25 U/L) by at least 18-fold.