bluuebunny/crossref_metadata_2025 huggingface dataset:
Parathyrin measured concurrently with free or total calcium in the differential diagnosis of hypercalcemia.
Authors: Boyd J C , Lewis J W , Slatopolsky E , Ladenson J H
Published: January 2020

We assessed the diagnostic utility of measuring C-terminal immunoreactive parathyrin (i-PTH) concurrently with free (CaF) or total (CaT) calcium in four groups of patients: (1) 91 patients with histologically proven primary hyperparathyroidism; (2) seven patients without histological evidence of hyperparathyroidism; (3) 70 patients with non-parathyroid malignancies with hypercalcemia; and (4) 28 similar patients without hypercalcemia. In patients in Group 1, the use of either calcium measurement along with i-PTH increased diagnostic accuracy from 95 to 99%. In Group 2, values consistent with primary hyperparathyroidism were obtained for 21% of samples with i-PTH assay alone, 29% with i-PTH and CaT, and 12% with i-PTH and CaF. Surprisingly, 36% of samples from both malignancy groups (3 and 4) had above-normal i-PTH values. In patients with malignancy and hypercalcemia (Group 3) the following percentages were classified as possibly being hyperparathyroid: 26% with i-PTH assay alone; 31% with i-PTH and CaT, and 24% with i-PTH and CaF. Our data indicate that (a) about a fourth of patients with nonparathyroid malignancies also have evidence of hyperparathyroidism as judged by this (and probably all other) i-PTH methods based on C-terminal antibody specificity and that (b) measuring CaF and i-PTH rather than CaT and i-PTH gives a small increase in diagnostic accuracy.
Metabolic abnormalities associated with diabetes mellitus, as investigated by gas chromatography and pattern-recognition analysis of profiles of volatile metabolites.
Authors: Rhodes G , Miller M , McConnell M L , Novotny M
Published: January 2020

Patterns of volatile metabolites in urine, as obtained by glass-capillary gas chromatography, were investigated by use of a nonparametric pattern-recognition method, in an effort to detect abnormalities associated with diabetes. We used threshold logic unit analysis on a data set consisting of normal subjects and those with diabetes mellitus, and could predict patterns for volatile metabolites as belonging to the proper class in 94.83% of the cases examined. In addition, a feature-extraction algorithm isolated those volatile constituents that are most useful in making the normal/diabetic classification. We used gas chromatography/mass spectrometry to identify important profile constituents. Finally, these same pattern-recognition methods indicated strong sex-related patterns in these volatiles.
Insulin degradation by human erythrocyte lysates.
Authors: Nerurkar S G , Gambhir K K
Published: January 2020

In vitro hemolysates of isolated human erythrocytes degrade 125I-labeled insulin. Ten- to 100-fold dilutions of the hemolysate give a proportionately decreased degradation of 125I-labeled insulin at 37 degrees C, while dilutions of up to eightfold do not. Like the control, diluted "Buffer G" containing 5 mmol/L Tris and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer alone, more than 500-fold dilutions of the hemolysate or boiled hemolysate (in buffer) caused negligible (less than 1%) degradation of the labeled insulin. We conclude that accurate insulin-binding data during erythrocyte insulin radioreceptor assay under optimum conditions (Clin. Chem. 23: 1590-1595, 1977) depend on avoiding or minimizing hemolysis.
Preincubation of serum aspartate aminotransferase with pyridoxal 5'-phosphate in the SMAC: comparison with revised DuPont aca method and recommended IFCC method.
Authors: Garber C C , Feldbruegge D H , Hoessel M
Published: January 2020

The method for continuous-flow assay of aspartate aminotransferase with the Technicon SMAC was modified to include preincubation of the serum enzyme with pyridoxal 5'-phosphate, to be consistent with the recommendations of IFCC and the Standards Committee of AACC. Preliminary estimates of the imprecision of the modified method on SMAC gave day-to-day standard deviations of 5.3 U/L at mean of 48 U/L (n = 66) and 6.2 U/L at 155 U/L (n = 61). Added bilirubin, sodium pyruvate, ascorbic acid, and endogenous lipids did not interfere. Comparison of results for 50 samples by this method with those by the manual IFCC method gave y = 1.1113x - 0.3 U/L, Sy/x = 4.4 U/L, and r = 0.997. Similar data are presented for the revised AST method for the DuPont aca discrete analyzer. Clinical data show that AST activities increase by as much as 200% when the serum is preincubated with pyridoxal 5'-phosphate.
Improved colorimetric assay for glycosylated hemoglobin.
Authors: Parker K M , England J D , Da Costa J , Hess R L , Goldstein D E
Published: January 2020

This colorimetric assay for glycosylated hemoglobin can be performed in 120 min with equipment available in most clinical laboratories. The glucose moiety of glycosylated hemoglobin is converted to 5-hydroxymethylfurfural by heating with oxalic acid for 60 min is an autoclave at 124 degrees C and 124 kPa (18 lb/in.2). The adduct formed by reacting 2-thiobarbituric acid with hydroxymethylfurfural is measured photometrically and results are expressed either as nanomoles of hydroxymethylfurfural or as fructose equivalents. Within-assay and between-assay coefficients of variation were less than 2% and less than 3%, respectively. Comparison of results for 50 patients' specimens as measured by the present assay and as analyzed for hemoglobin A1c by liquid chromatography showed excellent correlation (r = 0.98).
A homogeneous fluorescent immunoassay for human immunoglobulin M.
Authors: Worah D , Yeung K K , Ward F E , Carrico R J
Published: January 2020

We describe a homogeneous substrate-labeled fluorescent immunoassay for human IgM. In this competitive-binding method we use a fluorogenic substrate for Escherichia coli beta-galactosidase, N-(6-aminohexyl)-7-beta-galactosyl-coumarin-3-carboxamide, which is covalently coupled to IgM. The fluorescence emission intensity of the labeled IgM at 450 nm (with excitation at 400 nm) is negligible, but when beta-galactosidase is added, the acetal linkage of the galactosyl moiety is hydrolyzed and the product has a greatly enhanced fluorescence. Formation of this fluorescent product is inhibited when antibody specific for IgM is bound to the labeled protein. In competitive-binding reactions, IgM from the serum competes with the labeled IgM for antibody binding sites and consequently the fluorescence produced by the enzymic reaction is related to the IgM concentration. The working range of the assay is between 0.5 and 5.0 g of IgM per liter when a 50-fold predilution of the sera is used. The assay does not cross react significantly with immunoglobulins G or A.
New gas-liquid equilibration method: syringe tonometer.
Authors: Wallace W D , Cutler C A , Clark J S
Published: January 2020

This new apparatus for gas-liquid equilibration (tonometry) in a transportable vessel is designed for tonometry of blood or buffer solution in a specially designed syringe. Gas enters the syringe chamber through small holes in the tip of the syringe plunger and bubbles upward through the sample. The syringe plunger is a second chamber, which is used for warming and humidifying the gas before it enters the tonometer chamber. The entire syringe is housed in a transparent, temperature-controlled environment during equilibration. After equilibration, the sample is easily entered into a blood-gas analyzer. At most, gas-liquid O2/CO2 equilibration for 2.5 mL of buffer or blood requires less than 13 min. Comparisons with a standard thin-film tonometer show good agreement for pO2 and pCO2 over the range 0-93 kPa (0-700 mmHg) and 2-20 kPa (14-150 mmHg), respectively. The syringe tonometer eliminates contamination of the sample during transfer and transport to the analyzer, thus making tonometry more technique-independent. The apparatus is simple and easy to use, with definite advantages over existing methods of tonometry.
Two-hour assay for lutropin during ovulation.
Authors: Hay D L , Tasker P A , Johnston W I , Horacek I
Published: January 2020

A rapid lutropin assay with a 2-h incubation time and a second antibody/polyethylene glycol separation step is presented. Assay time is shortened by incubating at 37 degrees C and using relatively high concentrations of antibody and radioligand. The interval required for the antigen/antibody reaction varies directly with lutropin concentration, from 1 h for ovulation values to 8 h for low values. After a 2-h incubation, low concentrations have reached 80% of their equilibrium concentration. Separation of the bound fraction by use of combined second antibody/polyethylene glycol (50 g/L) gave one-third the nonspecific binding and as rapid a separation as with polyethylene glycol (180 g/L) alone. Optimal conditions for separating the immune complex were established, and separation was found to be independent of protein concentrations in urine or serum. This tested assay can detect increasing and ovulatory lutropin concentrations in urine or serum, but with some sacrifice in sensitivity.
Accuracy of some routine method used in clinical chemistry as judged by isotope dilution-mass spectrometry.
Authors: Björkhem I , Bergman A , Falk O , Kallner A , Lantto O , Svensson L , Akerlöf E , Blomstrand R
Published: January 2020

Serum from patients was pooled, filtered, dispensed, and frozen. This pooled specimen was used for accuracy control in 64 participating laboratories in Sweden. Mean values ("state-of-the-art" values) were obtained for creatinine, cholesterol, glucose, urea, uric acid, and cortisol. These values were compared with values obtained with highly accurate reference methods based on isotope dilution-mass spectrometry. Differences were marked in the case of determination of creatinine and cortisol. Concerning the other components, the differences between the state-of-the-art value and the values obtained with the reference methods were negligible. Moreover, the glucose oxidase and the oxime methods for determination of glucose and urea were found to give significantly lower values than the hexokinase and urease methods, respectively. We conclude that methods with a higher degree of accuracy are required for routine determination of creatinine and cortisol.
A kinetic standard for precise calibration of spectrophotometer cell temperature.
Authors: Adams P A , Berman M C
Published: January 2020

We describe a simple, highly reproducible kinetic technique for precisely measuring temperature in spectrophotometric systems having reaction cells that are inaccessible to conventional temperature probes. The method is based on the temperature dependence of pseudo-first-order rate constants for the acid-catalyzed hydrolysis of N-o-tolyl-D-glucosylamine. Temperatures of reaction cuvette contents are measured with a precision of +/- 0.05 degrees C (1 SD).
Suitability of control materials for determination of alpha-amylase activity.
Authors: Bretaudiere J P , Rej R , Drake P , Vassault A , Bailly M
Published: January 2020

The suitability of control materials for determination of alpha-amylase activity was assessed in comparison with reference groups of authentic human serum specimens containing alpha-amylase of either pancreatic or salivary origin, specimens from patients with no pancreatic pathology, and normal specimens to which porcine pancreatic alpha-amylase was added. After determination of alpha-amylase activity by 11 commonly used techniques (five different principles), the results were processed by both classical (linear representation, regression) and multivariate (correspondence analysis, principal-components analysis) statistical techniques. Specimens containing porcine pancreatic alpha-amylase did not behave like any of the other groups. We conclude that porcine enzyme should not be used for interlaboratory quality-control surveys or intermethod comparison studies. Determination of human salivary and pancreatic alpha-amylase showed intermethod biases similar to those for authentic patients' specimens. Human salivary alpha-amylase, both because of its behavior and its commercial availability, is a satisfactory source for alpha-amylase activity of quality-control specimens. The nature of the matrix (polyvinylpyrrolidone, albumin, delipidated serum, bovine serum, or human serum) little influenced the behavior of the specimens for any of the methods studied.
Determination of beta 2-microglobulin in human urine and serum by latex immunoassay.
Authors: Bernard A M , Vyskocil A , Lauwerys R R
Published: January 2020

This highly sensitive method for determination of beta 2-microglobulin (beta 2-m) in human urine or serum is based on direct agglutination by beta 2-m of latex particles on which an antibody against beta 2-m is adsorbed. The agglutination is quantified by counting the remaining unagglutinated particles, or by turbidimetry. A novel aspect of this method is the capability to prevent nonspecific agglutination of the antibody-coated particles by diluting them with an albumin solution of well-defined characteristics (pH, freshness, concentration) just before the assay. The assayable concentration range is 1--32 micrograms/L, the detection limit 0.5 micrograms/L. Within-assay CV, based on 10 determinations of beta 2-m in urine and serum at two different dilutions, ranged from 4.6 to 8.7%. Between-assay CV, calculated from 10 determinations of beta 2-m in urine and serum, was 10 and 8.4%, respectively. Analytical recovery of beta 2-m in urine averaged 97% and in serum 104% (n = 10). No component of urine or serum interfered. Coefficients of correlation for beta 2-m in urine or serum as measured by radioimmunoassay and latex immunoassay were 0.97 and 0.93, respectively. Concentrations of beta 2-m in serum and urine from 33 healthy men (ages 20 to 67 years) averaged 1.5 mg/l and 54 micrograms/g of creatine, respectively.
Quantitative differences in volatiles from healthy mouths and mouths with periodontitis.
Authors: Kostelc J G , Zelson P R , Preti G , Tonzetich J
Published: January 2020

It has been suggested that orally derived volatile aromatic amines may be of possible diagnostic use and may contribute to the etiology or pathogenesis of periodontal disease. Using gas chromatography and gas chromatography/mass spectrometry, we identified and quantitated pyridine and picolines in the headspace of incubated whole saliva from healthy and diseased subjects. The oral health of subjects was evaluated by four standard oral-health indices. Volatile aromatic amines were virtually absent from subjects with healthy oral cavities, but were present in the oral cavities of subjects with periodontitis to the extent of 636.4 (SEM 154.7) ng/5 mL of saliva. Pyridine and picolines in saliva of diseased subjects may be related to the disease process.
Alternatives to radioimmunoassay: labels and methods.
Authors: Schall R F , Tenoso H J
Published: January 2020

We review the following labels used as substitutes for radioisotopes in immunoassay systems: bacteriophages, chemiluminescence precursors, fluorochromes, fluorogens, fluorescence quenchers, enzymes, coenzymes, inhibitors, substrates, various particulates, metal atoms, and stable free radicals. New methods for performing immunoassays with these labels are described where appropriate. Methods that require no separation steps and offer special promise for easy automation are noted.
Fluoroimmunoassay of progesterone in human serum or plasma.
Authors: Allman B L , Short F , James V H
Published: January 2020

We describe a fluoroimmunoassay for progesterone in serum or plasma. The assay involves use of an antiserum to progesterone-11-hemisuccinate and a labeled antigen prepared by linking fluoresceinamine to progesterone-3-carboxymethyloxime by use of a mixed-anhydride procedure. Serum or plasma samples are extracted with hexane. After incubation of a portion of the evaporated extract with antiserum and labeled antigen, antibody-bound and free antigen are separated and the fluorescence of the bound fraction is measured. Separation is effected either by using ammonium sulfate to precipitate liquid-phase antiserum or by using a solid-phase antiserum: antiserum covalently linked to magnetizable cellulose particles, which are separated with a magnet. With either separation technique, analytical recovery, linearity, and precision were acceptable and results compared satisfactorily with those obtained with a conventional radioimmunoassay. The solid-phase assay is more precise and more technically convenient, but the performance of both fluoroimmunoassays was adequate for clinical use in the detection of ovulation.
Automated particle-counting immunoassay for digoxin.
Authors: Collet-Cassart D , Magnusson C G , Cambiaso C L , Lesne M , Masson P L
Published: January 2020

We describe a non-radioisotopic automated immunoassay for serum digoxin in the therapeutic range at 50 samples per hour by use of the particle-counting immunoassay technique and a special reagent, rheumatoid factor. Digoxin is determined by evaluating its inhibitory activity on the agglutination of digoxin-coated latex particles. The agglutinating system consists of the anti-digoxin IgG mixed with rheumatoid factor. This anti-IgG autoantibody reacts with IgG when they are aggregated or bound to a surface. Interference by serum proteins was prevented by pepsin digestion at 37 degrees C. Correlation with radioimmunoassay was r = 0.94 for 109 samples with concentrations between 0 and 5.7 micrograms/L. Analytical recovery overall averaged 102%. Within-assay precision (CV) ranged from 12.5% at 0.96 micrograms/L to 4.4% at 2.97 micrograms/L; between-assay precision varied from 8.4% at 0.75 micrograms/L to 5.8% at 2.92 micrograms/L.
Determination of clovoxamine concentration in human plasma by electron capture gas chromatography.
Authors: Hurst H E , Jones D R , Jarboe C H , deBree H
Published: January 2020

The antidepressant drug clovoxamine can be specifically and sensitively quantitated in human plasma by electron capture gas chromatography. Clovoxamine and the internal standard fluvoxamine are extracted into ethyl acetate from plasma at pH 12, back-extracted into phosphoric acid, and hydrolyzed at 90 degrees C to form ketone derivatives, which are then re-extracted into hexane for injection into the chromatograph. As little as 1 microgram of clovoxamine per liter of plasma can be measured. The coefficients of variation (CV) for th analysis at concentrations of 10 and 100 micrograms/L are respectively: within-run, 5.4% and 2.7%; between-run, 17.5% and 7.0%. When this assay was applied to plasma from individuals involved in an early clinical trial of clovoxamine, steady-state plasma concentrations ranged from 50 to 77 micrograms/L 3 h after a 50-mg oral dose of clovoxamine fumarate.
Further studies on plasma proteins, lipids, and dye- and drug-binding in a child with analbuminemia.
Authors: Frohlich J , Pudek M R , Cormode E J , Sellers E M , Abel J G
Published: January 2020

A previously reported patient with analbuminemia was re-investigated after 4 1/2 years, at age 6. The serum albumin concentration was 150 mg/L by radioimmunoassay. Most of the observed increase in total plasma protein over the 4 1/2 years was attributable to gamma-globulin. Concentrations of total and high-density lipoprotein cholesterol were increased; the esterified:free ratio and the lecithin-cholesterol acyltransferase activity were both normal. Albumin is apparently not essential for binding of lysolecithin generated by the acyltransferase-catalyzed reaction. The binding of bromphenol blue suggested that analbuminemic serum has about 25% of normal binding capacity for bilirubin (more than expected in a patient with analbuminemia), which may explain why newborns with this disorder do not develop kernicterus. Binding by the patient's plasma of diazepam (1020 mg/L) and warfarin (1040 mg/L), which bind primarily to albumin, as well as of propranolol (1.05 g/L), which binds primarily to alpha 1-acid glycoprotein, was also studied. The proportions of free diazepam (14.4%) and warfarin (4.8%) were about 10-fold normal. In contrast, the proportion of propranolol in the free form was decreased (4.5%). Evidently, other plasma proteins are partly compensating for the deficiency of albumin.
Determination of serum 17 alpha-hydroxyprogesterone by liquid chromatography.
Authors: Canalis E , Caldarella A M , Reardon G E
Published: January 2020

17 alpha-Hydroxyprogesterone, cortisol, and 11-deoxycortisol were extracted with methylene chloride, separated by liquid chromatography, identified by their retention times, and quantitated by monitoring the absorbance at 254 nm. The method is specific and sensitive to as little as 2.5 ng of 17 alpha-hydroxyprogesterone. Mean analytical recovery of added 17 alpha-hydroxyprogesterone was 99% (SD 11%) and the CV for the same or different assays ranged from 3.5 to 9.4%. 6 beta-Hydroxyprogesterone was used as the internal standard. Concentrations of 17 alpha-hydroxyprogesterone in serum of normal men and women were less than 2.5 micrograms/L, but women in the luteal phase of the menstrual cycle had higher values. Mean 17 alpha-hydroxyprogesterone content in serum from mixed cord blood of normal newborns was 28.1 (SD 13.8) micrograms/L. Results by this method correlated well (r = 0.97) with results by radioimmunoassay, but were somewhat higher.
Evaluation of a commercial kit for microchromatographic quantitation of hemoglobin A2 in the presence of hemoglobin S.
Authors: Baine R M , Brown H G
Published: January 2020

Commercial microcolumns introduced in 1976 by Helena Laboratories ("Hb A2 Quik Column") and by Isolab, Inc. ("Quik-Sep") provide a rapid, simple, accurate method for quantitation of hemoglobin A2 (Hb A2). However, these kits cannot be used for the quantitation of Hb A2 in the presence of slow-moving variants such as Hb S. Recently, Isolab, Inc., produced a new kit ("Quik-Sep Improved Hb A2 Test") for quantitation of both Hb A2 and Hb S. We compared results obtained with the new Isolab kit to results obtained with the original Tris/HCl method for quantitation of Hb A2 and Hb S. Blood was drawn from persons with sickle cell trait (A/S), sickle cell anemia (S/S), sickle cell/beta+ thalassemia (S/beta+ thal) and sickle cell/beta 0 thalassemia (S/beta 0 thal) and percentages of Hb A2 and Hb S were determined by each method. We found no significant differences in Hb A2 percentages by the two methods, and the coefficients of variation were similar. Both methods showed only slight overlap of Hb A2 values from subjects with some form of beta thalassemia and those with A/S or S/S. However, the Tris/HCl method consistently gave values for Hb S that were higher and closer to those expected, suggesting that the Isolab kit does not accurately quantitate Hb S.
Assay for plasma 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 by "high-performance" liquid chromatography.
Authors: Dabek J T , Härkönen M , Wahlroos O , Adlercreutz H
Published: January 2020

We describe a new, rapid, and simple column-chromatographic procedure for 25-OH vitamin D3 in plasma. The vitamin is extracted by use of Sep-pak C18 (octadecyl alkylated silicic acid), a short factory-packed reversed-phase column, and 25-OH vitamin D2 + 25-OH vitamin D3 fraction is eluted with methanol/water. The 25-OH D2 and 25-OH D3 are then well resolved on a high-resolution 3-micrometer silicic acid straight-phase liquid-chromatography column. The peaks are quantified against a 25-OH D3 standard by ultraviolet absorbance. Recovery was assessed by use of tritiated 25-OH D3. The within-assay coefficient of variation of the method was 5% and recovery 93%. The method was evaluated with 26 samples from control subjects and 17 samples from patients, seven with liver disease and 10 who had undergone ileo-ileostomy for hypercholesterolemia. The normal seasonal variation was observed for 25-OH D3 concentrations, and they correlated negatively and significantly with those of 25-OH D2. Post-ileo-ileostomy concentrations of 25-OH D3 in plasma were generally similar to those in normal individuals for the same reason (winter), but 25-OH D2 concentrations were insignificantly lower. The patients with chronic liver disease had significantly lower 25-OH D3 concentrations than normal persons but higher 25-OH D2 concentrations, with a significantly higher 25-OH D2/25-OH D3 ratio, indicating poor storage of vitamin D3.
Immunochemiluminometric assay for hepatitis B surface antigen.
Authors: Schroeder H R , Hines C M , Osborn D D , Moore R P , Hurtle R L , Wogoman F F , Rogers R W , Vogelhut P O
Published: January 2020

A novel "sandwich" immunoassay for hepatitis B surface antigen monitored by chemiluminescence is described. The method involves use of an antibody-coated microtitration plate and requires 100 micro L of test specimen. The antigen binds to the antibody during the first 2-h incubation and, after an intermediate wash step, the sandwich is completed by 2-h incubation with antibody to antigen that has been labeled with an isoluminol derivative. A final wash step follows. A luminometer, built in-house, adds "microperoxidase" and peroxide, to initiate chemiluminescence, and provides automated readout at 10-s intervals. Results compare well in specificity and sensitivity with those of a comparison radioimmunoassay procedure. Within- and between-assay variability (CV) is 7 to 13% (n = 6). All reagents are stable at 4 degrees C for at least several months. Use of a non-radioisotopic label in this assay avoids the stability problems and inconvenience associated with radioactivity.
Urinary urobilinogen determined by a mercuric chloride procedure.
Authors: Rupe C O , Fetter M C
Published: January 2020

In this quantitative assay, urinary urobilinogen is oxidized to urobilin with iodate in an acid medium, the pH is adjusted to 6 with sodium acetate, and the mixture is reacted with alcoholic HgCl2 solution, extracted with CHCl3, the measured spectrophotometrically at 513 nm. The artificial standards of previous methods have been replaced with crystalline stercobilin IX (commercially available), a urobilin closely related to the urinary urobilins. The reproducibility of the method, as assessed from 10 replicates of a single urine specimen to which urobilinogen was added, gave a coefficient of variation of 3.9%. Analytical recovery of urobilinogen added to urines was 90.4% (SD 14.5%). Bilirubin, biliverdin, mesobilirubin, coproporphyrin I, uroporphyrin I, and porphobilinogen do not interfere.
Radioimmunoassay for plasma thromboxane B2.
Authors: McCann D S , Tokarsky J , Sorkin R P
Published: January 2020

Platelet activity may play a major role in the acute phase of atherosclerotic cardiovascular disease. To assess such activity, an assay for plasma thromboxane B2, a prostaglandin metabolite unique to platelets, is needed. The radioimmunoassay described here is based on a nonequilibrium incubation followed by a solid-phase second-antibody separation of bound from free thromboxane B2. No prior purification is required. Values for 22 normal subjects averaged 39.0 (SD 24.6) ng/L. The thromboxane B2 concentration of a plasma sample was 20.3 ng/L as compared with 37 micrograms/L in the corresponding serum. Plasma thromboxane B2 concentrations before and after ingestion of aspirin differed significantly (p less than 0.025). The biological half-life of intravenously injected [3H]thromboxane B2 in rabbits was 20 min. At the end of 2 h, 85% of the label was accounted for in urine, 7% in liver, and 5% in lung. Our assay is simple, reproducible, sensitive, and specific. It can be used to reflect acute events involving platelet aggregation.
Two-site immunoenzymometric assay for thyrotropin in dried blood samples on filter paper.
Authors: Miyai K , Ishibashi K , Kawashima M
Published: January 2020

We describe a sensitive, simple, and rapid two-site immunoenzymometric assay for thyrotropin in dried blood samples on filter paper, for use in screening for neonatal primary hypothyroidism. In this method, two dried-blood spots of 3 mm diameter (equivalent to about 5.4 microliter of blood) are incubated overnight with anti-thyrotropin-beta-D-galactosidase complex in an anti-thyrotropin coated tube. Then the enzyme activity in the washed tube is determined fluorophotometrically. The range of thyrotropin measurable is 10 to 160 milli-int. units/L blood. Values for thyrotropin in dried blood samples determined by this method and those determined by radioimmunoassay correlated highly (r = 0.96).
Ferrozine iron and total iron-binding capacity method adapted to the ABA-100 Bichromatic Analyzer.
Authors: Mori L , Bekkering A , Traini J , Vanderlinden L
Published: January 2020

A sensitive method (Clin. Chem. 26: 327--331, 1980) for serum iron, in which the color reagent Ferrozine is used, is modified and adapted to the Abbott ABA-100 discrete analyzer. The standard curve is linear to at least 10 mg/L and the method showed day-to-day precision (CV) of 2.4% for a 1.03 mg/L sample (n = 63) and 1.9% for a 2.13 mg/L sample (n = 63). Lower values were obtained than with the modified continuous-flow technique of Giovanniello et al., but the correlation was good (r = 0.98). Bilirubin and copper do not interfere; hemoglobin and gross lipemia interfere only slightly. The total iron-binding capacity, based on Ramsay's method, was evaluated with regard to the effect of adding various amounts of magnesium carbonate. Results led us to use a ratio of approximately 180 mg of magnesium carbonate to each 5 micrograms of excess iron added. Day-to-day, the method for total iron-binding capacity gave a CV of 3.1% for a 2.55 mg/L sample, 2.8% for a 3.63 mg/L sample.
Direct determination of plasma copper and zinc in infants by atomic absorption with discrete nebulization.
Authors: Makino T , Takahara K
Published: January 2020

A new micromethod for the determination of copper and zinc is presented. Sample volumes can be as little as 10 (Cu) and 20 (Zn) microliter of plasma or serum, by using discrete (small sample volume) nebulization in place of conventional nebulization in place of conventional nebulization in atomic absorption spectrometry. The present method has slightly poorer precision than the conventional nebulization method, but has the advantages of requiring commercially available apparatus without any modification, involving simple sample preparation, and being time-saving. Results agree well with those by the trichloroacetic acid deproteinization method. In addition, this method is useful for pediatric samples, and we report reference intervals for full-term and premature infants, as well as adults.
Induction of O-deethylase activity as an index to exposure to coal-derived products and trace environmental pollutants.
Authors: Bostick W D , Kao J , Holland J M , Mrochek J E
Published: January 2020

The metabolism of the synthetic substrate 7-ethoxyresorufin is a selective measure of the activity of cytochrome P-448 monooxygenase, the subset of cytochrome P-450-mediated enzymes preferentially induced by polycyclic aromatic hydrocarbons and related compounds. 7-Ethoxycoumarin metabolism, on the other hand, reflects total (nonselective) cytochrome P-450 monooxygenase activity. Either substrate yields a single, highly fluorescent product, amenable to direct, sensitive assay with the portable centrifugal analyzer. We used three assays with liver microsomes from C57/BL6 mice for the short-term bioassay of the dose-dependent effects of exposure to selected environmental toxins, including petroleums, polychlorinated biphenyls, and their oxidative degradation products.
Design and evaluation of statistical control procedures: applications of a computer "quality control simulator" program.
Authors: Westgard J O , Groth T
Published: January 2020

A computer simulation program has been developed to aid in designing and evaluating statistical control procedures. This "QC stimulator" (quality control) program permits the user to study the effects of different factors on the performance of quality-control procedures. These factors may be properties of the analytical procedure, characteristics of the instrument system, or conditions for the quality-control procedure. The performance of a control procedure is characterized by its probability for rejection, as estimated at several different magnitudes of random and systematic error. These performance characteristics are presented graphically by power functions-plots of the probability for rejection vs the size of the analytical errors. The utility of this stimulation tool is illustrated by application to multi-rule single-value procedures, mean and range procedures, and a trend analysis procedure. Careful choice of control rules is necessary to minimize false rejections and to optimize error detection with multi-rule procedures. Control limits must be carefully calculated for optimum performance of mean and range procedures. The level of significance for testing control must be carefully selected for the trend analysis procedure.
Free-zone electrophoresis in glass capillaries.
Authors: Jorgenson J W , Lukacs K D
Published: January 2020

A simple theory of zone electrophoresis in open-tubular capillaries is developed. According to this theory, to achieve the highest resolution of zones, tubes with as small an inside diameter as possible should be used in combination with as high an applied voltage as feasible. To test this approach, we performed electrophoresis in glass capillaries with an internal diameter of 75 micron and a length of 100 cm. A special fluorescence detector was used to detect fluorescent zones while they migrated inside the capillary. With the application of 30 kV potentials to this system, rapid and efficient separations of amino acids, peptides, and urinary amines were demonstrated. In all cases fluorescent derivatives were necessary for detection. Preliminary results are encouraging, and with further development of sensitive detection devices, applications in clinical analyses may be feasible.
Automated in-line ratio-correcting filter fluorometer.
Authors: Khalil O S , Routh W S , Lingenfelter K , Carr D B , Ladouceur P
Published: January 2020

We have developed a novel optical arrangement for the Abbott VP bichromatic analyzer, converting it into a fluorometer upon insertion of a specially designed filter carriage. Fluorescence intensity is measured by using straight-through excitation geometry and is corrected for fluctuations in light-source intensity by using the attenuated transmitted beam through the solution as a reference. The modification allows switching from the absorbance to fluorescence mode without an auxiliary light source or a major hardware change. The detection limit for an experimental prototype was estimated as 192 pmol of fluorescein per liter. In an application to a fluorescence immunoassay for theophylline in patients' sera, the data (y) correlated well with results by an enzyme immunoassay procedure (EMIT), giving a correlation equation of y = 1.849 + 0.988x (r = 0.969). A fluorometric standard curve for glucose and some performance data are also presented.
An enzymic, reaction-rate assay for serum creatinine with a centrifugal analyzer.
Authors: Jaynes P K , Feld R D , Johnson G F
Published: January 2020

We describe a procedure for specific, rapid, kinetic determination of creatinine, in which a manual coupled-enzyme micro-scale assay is adapted to a centrifugal analyzer. The creatinine reaction is ultimately linked to NADH utilization, which is measured by the absorbance change at 340 nm. This procedure requires 15 microL of serum and the standard curve is linear to a creatinine concentration of 200 mg/L. A four-point kinetic algorithm allows the dynamic range of the assay to be extended without sacrificing sensitivity, and makes a separate serum blank unnecessary. The within-run precision (CV) for samples with a creatinine concentration of 11 and 52 mg/L was 5.6 and 2.4%, respectively; day-to-day CV for a creatinine concentration of 11 mg/L was 7.7% (n = 21). We compared this procedure with a kinetic Jaffé procedure, with excellent agreement (r = 0.996; y = 0.96x + 2.4 mg/L). Bilirubin, non-esterified fatty acids, and ketone bodies do not affect creatinine determinations by this method; thus the method is especially useful for monitoring the renal function of diabetics.
Detergent activation of the binding protein in the folate radioassay.
Authors: Hansen S I , Holm J , Lyngbye J
Published: January 2020

A minor cow's whey protein associated with beta-lactoglobulin is used as binding protein in the competitive radioassay for serum and erythrocyte folate. Seeking to optimize the assay, we tested the performance of binder solutions of increasing purity. The folate binding protein was isolated from cow's whey by means of CM-Sepharose CL-6B cation-exchange chromatography, and further purified on a methotrexate-AH-Sepharose 4B affinity matrix. In contrast to beta-lactoglobulin, the purified protein did not bind folate unless the detergents cetyltrimethylammonium (10 mmol/L) or Triton X-100 (1 g/L) were present. Such detergent activation was not needed in the presence of serum. There seems to be a striking analogy between these phenomena and the well-known reactivation of certain purified membrane-derived enzymes by surfactants (lipids/detergents).
Evaluation of a commercially available radioimmunoassay kit for measurement of doxorubicin in plasma.
Authors: Piall E , Aherne G W , Marks V
Published: January 2020

We evaluated a commercially available (Diagnostic Biochemistry Inc.) doxorubicin 125I radioimmunoassay kit. This kit gave a high apparent doxorubicin concentration (greater than 12 micrograms/L), which was not linearly related to dilution, for two pools of normal human serum and plasma and also for samples collected from patients before they received the drug. In contrast, a doxorubicin 3H radioimmunoassay developed by us gave a low blank (2 micrograms/L), which was linearly related to dilution, for the same pools and patients' samples. Doxorubicin concentrations in the plasma of patients receiving the drug were compared by the two methods; the kit gave results five- to 10-fold those obtained with our assay. High nonspecific interference by serum and plasma as measured by the 125I radioimmunoassay must therefore be borne in mind by users of the kit, and we suggest that results should be corrected for these nonspecific effects.
Turnover rate of skeletal alkaline phosphatase in humans.
Authors: Posen S , Grunstein H S
Published: January 2020

Two patients with Paget's disease of bone were subjected to plasmapheresis. Alkaline phosphatase activities of serum declined sharply, but returned to preplasmapheresis values within eight to 10 days. The biological half-life of circulating skeletal alkaline phosphatase, as calculated from these experiments, is between 1.12 and 2.15 days.
Stability of frozen liquid control sera for assay of cholesterol in high-density lipoprotein.
Authors: Demacker P N , Hijmans A G , van Sommeren-Zondag D F , Jansen A P
Published: January 2020

Liquid serum pools with low-, normal-, or above-normal concentration of high-density lipoprotein cholesterol were prepared by selection and dilution of sera having low lipoprotein content or by enrichment with concentrated high-density lipoprotein. Stability of the serum pools depended on storage conditions. On storage between -2 and -12 degrees C, the high-density lipoprotein cholesterol content decreased. At a constant temperature of -19 to -21 degrees C the concentrations remained stable for more than 18 months. The imprecision (CV) of the high-density lipoprotein cholesterol assay during this period as established with enzymic cholesterol analysis (Clin. Chem. 26: 1780-1786, 1980) of these serum pools was between 2.7 and 4.8% (n = 51). Serum pools prepared and stored as described are suitable for internal quality-control procedures. In external quality-control trials these sera may be superior to the commercially available lyophilized lipid control sera.
Immunoinhibition and automated column chromatography compared for assay of creatine kinase isoenzyme MB in serum.
Authors: Bayer P M , Boehm M , Hajdusich P , Hotschek H , Koehn H , Unger W , Wider G
Published: January 2020

We examined sera from six different groups of patients for CK-MB activity by means of two commercially available tests, an immunoinhibition method (E. Merck) and the CK-MB test as used with the aca (Du Pont). In the first group of patients (suspicion of myocardial infarction) the correlation between the two methods was good: r = 0.9191, y = 1.068x -- 0.888, x = 18.7 U/L, y = 19.0 U/L. In the second group, patients with high adenylate kinase activity, no interference was detectable on the aca, whereas the immunoinhibition method yielded falsely high CK-MB values. The third group consisted of persons with macro-CK-BB in their serum. In the immunoinhibition test these patients usually showed a high CK-MB:total CK ratio, whereas such results were rarely found for the aca. The fourth group, patients with a different electrophoretic mobility of their CK-isoenzymes (migration of an active band towards the cathode), were detected by the immunoinhibition method (high ratio of CK-MB to total CK), but not with the aca. In the presence of free CK-BB (group five) the immunoinhibition test resulted in "falsely" high CK-MB values, whereas CK-BB was retained on the column of the aca. In skeletal muscle diseases (group six) results by the two methods differed, values for CK-MB on the aca being much higher. It was demonstrated experimentally that this was due to CK-MM with altered surface charge.
Radioimmunoassay and chemical ionization/mass spectrometry compared for plasma cortisol determination.
Authors: Lindberg C , Jönsson S , Hedner P , Gustafsson A
Published: January 2020

We describe a method for determination of cortisol in plasma and urine, based on chemical ionization/mass spectrometry with deuterium-labeled cortisol as the internal standard. The within-run precision (CV) was 2.5-5.7%, the between-run precision 4.6%. Results by this method were compared with those by a radioimmunological method (RIANEN Cortisol, New England Nuclear) for 395 plasma samples. The latter method gave significantly higher (approx. 25%) cortisol values.
Evaluation of four assay methods for determination of tobramycin in human serum.
Authors: Acton W J , Van Duyn O M , Allen L V , Flournoy D J
Published: January 2020

Four assay procedures for tobramycin in serum--enzyme immunoassay (I), substrate-labeled fluorescent immunoassay (II), radioimmunoassay (III), and bioassay (IV)--were compared and evaluated by replicate and analytical recovery studies. I and II were about 50% more precise than III and IV. II was substantially more nearly accurate than the other methods and also gave the best reproducibility (correlation coefficient 0.992 between-day). The least expensive method was IV. Ease of handling favored I and II. Overall, we find II to be the most acceptable procedure for use in the clinical laboratory.
Laser nephelometry and radial immunodiffusion compared for immunoglobulin quantification in pathological sera.
Authors: Cloppet H , Francina A , Coquelin H , Boucaud-Maître Y , Hutinel P , Creyssel R
Published: January 2020

We evaluated nephelometers from Behring, Hyland, and Beckman for IgG, IgA, and IgM quantitation in sera from patients with monoclonal gammopathies. The intra-batch precision of each instrument for each immunoglobulin class and for different concentrations of the same immunoglobulin was compared to the one obtained with the radial immunodiffusion method. No nephelometer showed a clearly better precision. The correlation with cellulose acetate electrophoresis was good for each of the three nephelometers. The mean value by the radial immunodiffusion method was higher than corresponding determinations by nephelometry.
Liquid-chromatographic determination of urinary 5-hydroxy-3-indoleacetic acid, with fluorescence detection.
Authors: Rosano T G , Meola J M , Swift T A
Published: January 2020

We describe and evaluate a procedure for measuring urinary 5-hydroxy-3-indoleacetic acid by "high-performance" liquid chromatography. After a simple organic extraction, the analyte and internal standard are chromatographed on a reversed-phase column and are detected by native fluorescence. The detection limit (3 ng per injection), between-day precision (CV 5.2%), absolute recovery (70%), analytical recovery (99%), and working linear range (up to 15 mg/L) have been determined. Compared with colorimetric results with nitrosonaphthol, values obtained with the chromatographic method are significantly lower. Reference values and clinical experience with the method are reported. The method is simple, free from interferences, and suitable for use in routine analysis in the clinical laboratory.
1-naphthyl phosphate: specifications for high-quality substrate for measuring prostatic acid phosphatase activity.
Authors: Bowers J L , Bowers G N
Published: January 2020

Ten lots of sodium 1-naphthyl phosphate were compared by spectrophotometry, high-performance liquid chromatography, and kinetic measurements of the activity of human prostatic acid phosphatase (EC 3.1.3.2) in serum. Two lots were readily identified as the 2-naphthyl phosphate salt by spectrophotometry and liquid chromatography. Four of the remaining eight lots of sodium 1-naphthyl phosphate met the following specifications: (a) sodium 1-naphthyl phosphate content greater than 80% by A286nm measurements (epsilon286nm1-NP = 5630 L.mol-1.cm-1) and by enzymic conversion to 1-naphthol (epsilon332nm1-N = 7560 L.mol-1.cm-1), (b) free 1-naphthol less than 3 mmol/mol, (c) inorganic phosphate less than 10 mmol/mol, and (d) the catalytic activity concentration greater than 98% maximum by absorbance assay and greater than 90% maximum by spectrofluorometric assay during simultaneous comparisons of several substrates. The need for detailed specifications and the testing of each batch of sodium 1-naphthyl phosphate is readily demonstrated by this study.
Comparison of two isotope dilution/mass spectrometric methods for determination of total serum cholesterol.
Authors: Schaffer R , Sniegoski L T , Welch M J , White V E , Cohen A , Hertz H S , Mandel J , Paule R C , Svensson L , Björkhem I , Blomstrand R
Published: January 2020

Isotope dilution/mass spectrometric methods for total serum cholesterol, developed separately at the Karolinska Institutet (KI) and the National Bureau of Standards (NBS), were compared by applying them to a common set of serum pools. A search for the cause of a systematic difference of a few percent in results from the two methods revealed that the KI cholesterol standard contained lathosterol, which interfered with the calibration of the method. With NBS Standard Reference Material cholesterol used for new analyses at the KI, the average difference in mean values dropped to 0.2%. The NBS results are more precise. This is attributed to the protocols NBS used for sample preparation and mass spectrometry. However, these protocols make the NBS method more complex and time-consuming. A recent critical article on the use of this technique for total cholesterol is also examined.
Radioimmunoassay for pregnancy-associated plasma protein A.
Authors: Sinosich M J , Teisner B , Folkersen J , Saunders D M , Grudzinskas J G
Published: January 2020

A specific and highly sensitive radioimmunoassay for determination of pregnancy-associated plasma protein A in human serum is described. The minimum detection limit for this protein was 2.9 micrograms/L. The within- and between-assay coefficients of variation were 4.0 and 4.5%, respectively. The circulating protein was detected within 32 days of conception in eight normal pregnancies and within 21 days in a twin pregnancy. Circulating concentrations in the mother at term were consistently higher (10-fold) than in matched amniotic fluid; none was detected in the umbilical circulation. This protein was also detected in the circulation of patients with hydatiform mole. This assay will permit investigations into the clinical evaluation of measurements of the protein during early pregnancy and trophoblastic disease.