bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis for Transaminases in Serum with an Amperometric Glutamate Electrode
Authors: Compagnone D , Federici G , Massoud R , Santoro L , Anichini M , Palleschi G
Published: January 2020

We determined transaminases in human blood serum with an amperometric glutamate biosensor. The probe was a hydrogen peroxide sensor assembled with appropriate selective membranes to enhance the probe specificity and lifetime. Calibration curves of glutamate were linear in the range 1-1000 mumol/L, with a response time of < 1 min. This probe was subsequently applied to the measurement of activities of aspartate and alanine aminotransferases in human sera. Analytical recovery studies demonstrated the suitability of the glutamate sensor by measuring 91-99% of added glutamate, 92-106% of added aspartate aminotransferase, and 101-105% of added alanine aminotransferase. Transaminase activity measured in 80 sera correlated well with results obtained with a spectrophotometric procedure.
Affinity Binding Assay of Glycohemoglobin by Two-Dimensional Centrifugation Referenced to Hemoglobin A1C
Authors: Fiechtner M , Ramp J , England B , Knudson M A , Little R R , England J D , Goldstein D E , Wynn A
Published: January 2020

We describe an automated assay of glycohemoglobin performed with the Abbott Vision analyzer. The assay is based on batch affinity-extraction with 3-aminophenylboronic acid-derivatized agarose beads. Reagents are packaged in a disposable test pack. Whole-blood specimens are hemolyzed with saponin within a glass capillary tube inserted into the test pack. The sample is automatically diluted with, mixed with, and separated from the solid-phase reagent. Bichromatic absorbance readings are used to calculate the percentage of hemoglobin bound. Based on the linear correlation between affinity-measured glycohemoglobin and HPLC-measured hemoglobin A1c, the percentage of hemoglobin bound is converted to a "standardized %HbA1c" result by use of regression parameters stored during a calibration run. The combination of affinity methodology with standardization by reference to HPLC produces values directly comparable with those obtained by methods specific for HbA1c. The method produces 10 results within 15 min. The assay operates with CVs < 5%, and the results correlate highly with those by ion-exchange and affinity minicolumn methods, and by ion-exchange HPLC.
Discrepancies Between Sodium Concentrations Measured by the Kodak Ektachem 700 and by Dilutional and Direct Ion-Selective Electrode Analyzers
Authors: Stone J A , Moriguchi J R , Notto D R , Murphy P E , Dass C J , Wessels L M , Freier E F
Published: January 2020

We have identified rare (approximately 0.2% of all samples), but clinically significant, discrepancies between serum or plasma sodium concentrations measured with the Kodak Ektachem 700's direct ion-selective electrode (ISE) method and concentrations measured with two other analyzers: the Beckman Synchron CX3's dilutional ISE instrument and the Radiometer KNA2 instrument for sodium-potassium analysis by the direct ISE method. The differences do not appear to be related to any previously identified sources of discrepancy, such as variations in triglycerides, bicarbonate, total protein, albumin, or gamma-globulin, the presence of paraproteins, or interference by benzalkonium chloride from heparinized catheters. They occurred despite the use of Gen 04 reference fluid on the Ektachem. We could not identify any drug or family of drugs that the patients had taken in common and that might influence the results. Until this problem is resolved, Ektachem users should be aware of the potential for discrepancies of > 6 mmol/L in measurements of sodium concentrations.
DNA Diagnosis with Mutation-Specific Artificial Methylation Sites: Application to Rapid Screening of Δ F508
Authors: Petty E M , Gold E , Bale A E
Published: January 2020

Many polymerase chain reaction (PCR)-based methods for diagnosis of minute mutations are suboptimal for automated screening because of their reliance on gel electrophoresis or probe hybridization. In the method reported here, PCR products containing artificial methylation sites are analyzed by measuring incorporation of radiolabeled methyl groups. Primers are designed to amplify the possible mutation-containing region such that the 3' end of one primer lies adjacent to the possible mutation. Sequence modification near that end creates either a mutation- or wild type (WT)-specific artificial methylation site in the PCR product. The product is briefly incubated with an appropriate DNA methylase and tritiated S-adenosylmethionine ([3H]SAM), separated from free SAM by column chromatography, and analyzed for incorporation of tritium. Applying this technique to the cystic fibrosis delta F508 deletion, we accurately diagnosed five homozygotes, five heterozygotes, and five normal individuals within 40 min of PCR completion. The method can be generalized to rapid, automated detection of a variety of point mutations and small deletions.
Direct Determination of Zinc in Serum by Zeeman Atomic Absorption Spectrometry with a Graphite Furnace
Authors: D'Haese P C , Lamberts L V , Vanheule A O , De Broe M E
Published: January 2020

We developed a precise and accurate graphite furnace atomic absorption spectrometric method for the direct determination of zinc in serum. Serum samples are analyzed after 20-fold dilution with water of ultrapure analytical grade. No other reagent is used, from the moment of sampling until measurement. During atomization, the argon flow is kept at 150 mL/min instead of gas stop, to decrease the sensitivity and thus allow lower dilution ratios. Zinc concentrations are determined against a serum-matched calibration curve. Graphite tubes are uncoated and no L'vov platform is used. Between-run CVs were 5.9%, 3.5%, and 1.9% for serum zinc concentrations of 0.93, 1.15, and 1.43 mg/L, respectively. The characteristic mass was 9 pg, and the detection limit (meanblank + 3SDblank) was 0.060 mg/L.
Reference Values for Immunoglobulin Kappa and Lambda Light Chains and the Kappa/Lambda Ratio in Children's Serum
Authors: Saitta M , Iavarone A , Cappello N , Bergami M R , Fiorucci G C , Aguzzi F
Published: January 2020

We analyzed 708 serum samples from healthy children and adolescents by immunonephelometry to obtain reference values for the immunoglobulin kappa (kappa) and lambda (lambda) light chains and for their ratio at a time of life when immunoglobulin synthesis is maturing and continually being stimulated. The lambda chain concentration that is to be maintained throughout the child's life is reached very early, just after 1 year, whereas the concentration of the kappa chains, which increases gradually, reflects the concentration of the immunoglobulins as a whole. These reference values may be useful for studying kappa and lambda chains in illnesses involving the immune system in children.
Chemical Nature of Intestinal-Type Alkaline Phosphatase in Human Kidney
Authors: Nishihara Y , Hayashi Y , Adachi T , Koyama I , Stigbrand T , Hirano K
Published: January 2020

Approximately 10% of the alkaline phosphatase activity in human kidney is derived from the intestinal-type alkaline phosphatase isoform, which can be differentiated from adult intestinal alkaline phosphatase by selective reactivity with monoclonal antibodies. The NH2-terminal sequence of the renal intestinal-type alkaline phosphatase was shown to be identical to sequences of the adult and meconial alkaline phosphatases except for the NH2-terminal valine residue, which is missing in the renal intestinal-type enzyme. Incubation of purified meconial alkaline phosphatase with kidney homogenate resulted in removal of the NH2-terminal valine residue, indicating the presence of aminopeptidases in kidney that catalyze this hydrolysis. Furthermore, the oligosaccharide chains of the renal intestinal-type alkaline phosphatase were shown to differ from those of meconial and adult intestinal alkaline phosphatases, as revealed by lectin affinity chromatography. The heterogeneity of the intestinal-type alkaline phosphatase can therefore be generated both by partial peptide bond hydrolysis and differences in glycosylation.
A Tool for the Design and Evaluation of Alternative Quality-Control Procedures
Authors: Hatjimihail Aristides T
Published: January 2020

I have developed an interactive microcomputer simulation program for the design, comparison, and evaluation of alternative quality-control (QC) procedures. The program estimates the probabilities for rejection under different conditions of random and systematic error when these procedures are used and plots their power function graphs. It also estimates the probabilities for detection of critical errors, the defect rate, and the test yield. To allow a flexible definition of the QC procedures, it includes an interpreter. Various characteristics of the analytical process and the QC procedure can be user-defined. The program extends the concepts of the probability for error detection and of the power function to describe the results of the introduction of error between runs and within a run. The usefulness of this approach is illustrated with some examples.
Localizing the Site of Hematuria by Immunocytochemical Staining of Erythrocytes in Urine
Authors: Janssens Pim M , Kornaat Nicolette , Tieleman Remco , Monnens Leo A H , Willems Johannes L
Published: January 2020

We have further explored the immunocytochemical staining method to discriminate renal and nonrenal hematuria, reported by Abrass and Laird (Am J Kidney Dis 1987;9: 44-50). After fixation on slides with acetone, erythrocytes in urine were stained with antiserum against human Tamm-Horsfall protein. Reactions were made visible by using either a fluorescent second antibody or a biotinylated second antibody, avidin, and biotinylated horseradish peroxidase, producing an insoluble reaction product. The staining methods were validated with material from clinically diagnosed cases of hematuria of renal or nonrenal origin. In material from kidney transplantation patients, in samples from the catheter that were presumed to contain renal erythrocytes, 84.7% and 80.1% of the erythrocytes stained by the immunofluorescence and immunoperoxidase methods, respectively, whereas in samples from the catheter that were supposed to contain nonrenal erythrocytes, 9.3% and 13.1% of the cells stained. In a group of nontransplantation patients with various causes of renal hematuria, 87.3% and 89.8% of the erythrocytes in urine stained with the immunofluorescence and immunoperoxidase methods, respectively, whereas in samples from patients with hematuria of known nonrenal origin, 12.9% and 12.4% of the cells stained. Staining of erythrocytes in renal and nonrenal hematuria was significantly different (P less than 0.001) and better discriminated between renal and nonrenal hematuria than did inspection of the morphology of erythrocytes in urine.
When Do Gut Flora in the Newborn Produce 3-Phenylpropionic Acid? Implications for Early Diagnosis of Medium-Chain Acyl-CoA Dehydrogenase Deficiency
Authors: Bennett Michael J , Bhala Ajay , Poirier Stephanie F , Ragni Marie C , Willi Steven M , Hale Daniel E
Published: January 2020

Urinary excretion of 3-phenylpropionylglycine (PPG) is a diagnostic marker for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. PPG is derived from 3-phenylpropionic acid (PPA), a product of anaerobic bacterial metabolism in the gut. To determine when the infant gut was colonized with PPA-producing bacteria, we cultured stool in prereduced thioglycollate broth from 93 apparently healthy infants. We analyzed the products of bacterial metabolism by gas chromatography/mass spectrometry for the presence of PPA. Trend analysis demonstrated a significant difference (P less than 0.001) in PPA production between early and later infancy. PPA was not detected in 84% of media isolated from stool collected from infants younger than four months. For older infants, 67% of the samples were PPA-positive. Thus, because the normal gut is not sufficiently colonized with PPA-producing bacteria before three to four months of age, PPG analysis alone is not a sensitive marker for the early detection of MCAD deficiency. Using stable isotope dilution mass spectrometry, we measured PPG and n-hexanoylglycine (HG) excretion in two well newborns with MCAD deficiency. HG, believed to be an endogenous metabolite associated with MCAD deficiency, was consistently above normal in all urine samples.
Modified Immunoradiometric Assay of Parathyroid Hormone-Related Protein: Clinical Application in the Differential Diagnosis of Hypercalcemia
Authors: Pandian M R , Morgan Craig H , Carlton Esther , Segre Gino V
Published: January 2020

We have developed a sensitive, specific solid-phase immunoradiometric assay (IRMA) of parathyroid hormone-related protein (PTH-RP) with use of affinity-purified polyclonal immunoglobulins. Antibodies recognizing PTH-RP(37-74) are immobilized to a polystyrene bead to "capture" analytes from the sample; antibodies to epitopes within the 1-36 amino acid region of PTH-RP are labeled with 125I. This IRMA recognizes PTH-RP(1-74) and PTH-RP(1-86) equivalently, but does not detect N-terminal or C-terminal fragments of PTH-RP, intact human parathyrin (PTH), or fragments of PTH. PTH-RP is not stable in plasma at 3-5 degrees C or room temperature, but a mixture of aprotinin (500 kallikrein units/L) and leupeptin (2.5 mg/L) improves PTH-RP stability in blood samples. In plasma collected in the presence of these protease inhibitors from normal volunteers and patients with various disorders of calcium metabolism, PTH-RP concentrations were above normal (greater than 1.5 pmol/L) in 91% (42 of 46) of patients with hypercalcemia associated with nonhematological malignancy. In plasma from patients with other hypercalcemic conditions (e.g., primary hyperparathyroidism, sarcoidosis, and vitamin D excess), PTH-RP was undetectable. Above-normal concentrations of PTH-RP and total calcium decreased to normal in a patient with an ovarian cyst adenocarcinoma after surgical removal of the tumor. We conclude that PTH-RP is related to and probably the causative agent of hypercalcemia in most patients with cancer, and that measurements of PTH-RP are useful in the diagnosis and management of patients with tumor-associated hypercalcemia.
Identification of Urinary Calculi by Raman Laser Fiber Optics Spectroscopy
Authors: Hong T D Nguyen , Phat D , Plaza P , Daudon M , Dao Nguyen Quy
Published: January 2020

Human calculi of various compositions were automatically identified by using near-infrared excitation Fourier-transform Raman spectrometry. After having built a 150-compound Raman library as a first step, we used a commercial software for infrared spectra (program BIRSY, from Brüker) to determine the composition of different calculi. Good results were obtained for both classical Raman laser and Raman laser fiber optics spectroscopies. With the use of a natural biological medium, e.g., urine, to mimic as closely as possible clinical in vivo conditions, the automatic search correctly identified the calculus composition with relatively good test quality; in some mixtures, however, the results can only be considered semi-quantitative at present, even after smoothing of the spectra.
Improving Accuracy of Glucose Oxidase Procedure for Glucose Determinations on Discrete Analyzers
Authors: Leary N O , Pembroke A , Duggan P F
Published: January 2020

We describe a rapid kinetic glucose oxidase (EC 1.1.3.4) procedure for quantifying glucose. Glucose oxidase concentration was reduced from the more usual 20 kU/L to 4 kU/L, and pH was reduced from 7.0 to 6.6. Potassium ferrocyanide (20 mumol/L) and ascorbate oxidase (1 kU/L) were incorporated in the procedure. The assay results vary linearly with glucose concentration from 0 to 50 mmol/L and are unaffected by bilirubin concentrations less than or equal to 600 mumol/L, hemoglobin less than or equal to 12 g/L, Intralipid less than or equal to 4 g/L, urate less than or equal to 1 mmol/L, and ascorbate less than or equal to 2.0 mmol/L. The assay is readily adaptable to most open-system analyzers.
Simultaneous Assay of Corticosterone and Cortisol in Plasma by Reversed-Phase Liquid Chromatography
Authors: Hariharan M , Naga S , VanNoord T , Kindt E K
Published: January 2020

We have developed a simple, specific, and sensitive reversed-phase liquid-chromatographic method for accurate and simultaneous analysis of corticosterone and cortisol in human plasma. We achieved a detection limit of 300 ng/L for both steroids by modifying the old solid-phase extraction method to make use of "Tef Elutor" C18 columns, using a minibore (100 x 2 mm) analytical column, and using an ultraviolet detector with a 10-mm-pathlength flow cell. With the new extraction method absolute extraction efficiencies were greater than 90% for all the analytes, including the internal standard, flumethasone. The mobile phase was water (containing 5 mL of triethylamine per liter and citric acid to adjust the pH to 6.5), tetrahydrofuran, and acetonitrile (82/10/8 by vol). The average interassay CV for corticosterone at 0-25 micrograms/L was 6.5%; that for cortisol at 0-300 micrograms/L was 3.8%. The analytical recovery relative to the internal standard was 100.2% for cortisol and 102.6% for corticosterone. Possible interferences from drugs and other steroids were studied.
Free α-Subunit, Free β-Subunit of Human Chorionic Gonadotropin (hCG), and Intact hCG in Sera of Healthy Individuals and Testicular Cancer Patients
Authors: Madersbacher S , Klieber R , Mann K , Marth C , Tabarelli M , Wick G , Berger P
Published: January 2020

To determine the serum concentrations of human chorionic gonadotropin (hCG), its free beta-subunit (hCG beta), and the free alpha-subunit (free alpha) common to all human glycoprotein hormones under physiological and pathological conditions, we developed monoclonal antibody-based immunoenzymometric assays. Free alpha-subunit was detected in the sera of all healthy individuals of both sexes; hCG was measurable in sera of 54% of the men, and 46% were positive for free hCG beta; in nonpregnant women, 69.5% were positive for hCG, 68.4% for the free beta-subunit. Pathological conditions, i.e., hCG-producing tumors, were studied in vitro and in vivo. In vitro, the concentrations of hCG, free hCG beta, and free alpha in tissue-culture supernates of a choriocarcinoma cell-line ("JAR") showed a parallel pattern during time-course analysis. In vivo, in long-term follow-up studies of 13 patients with testicular cancer, serum concentrations of the three analytes paralleled each other, whether the disease was in remission or not. Because of a selective increase of free hCG beta and free alpha in 27% of seminomatous tumor patients and in 13% of the nonseminomatous patients, the percentage of tumor-marker-positive sera was increased from 15% to 42% and 57% to 70%, respectively, by the additional measurement of free hCG beta and free alpha. Thus hCG, free hCG beta, and free alpha are physiologically present in a high percentage of the sera from healthy men, and the determination of free hCG beta and free alpha, although not of prognostic value, improves the diagnostic possibilities in patients with testicular cancer.
Practical Approach for Determining Glomerular Filtration Rate by Single-Injection Inulin Clearance
Authors: Jung K , Henke W , Schulze B D , Sydow K , Precht K , Klotzek S
Published: January 2020

We compared the glomerular filtration rate as measured by a single-injection inulin clearance with that measured by a standard isotope method with 99mTc-labeled diethylenetriaminopentaacetic acid in 21 subjects with glomerular filtration rates greater than 35 mL/min. After a bolus injection of 5 g of inulin, blood samples were taken 20, 45, 90, 120, 145, 180, and 240 min afterwards. Inulin was measured by optimized chemical or enzymatic methods of high analytical sensitivity to determine inulin at low concentrations. We used the one-compartment model and inulin concentrations measured at two sampling times to calculate the glomerular filtration rate from the data of the disappearance curve of inulin. Inulin concentrations at 20 and 240 min after injection of the inulin bolus were suited to estimate glomerular filtration rate by this procedure, resulting in values (y) comparable with those obtained by isotope technique (x). The relationship to the isotope technique was characterized by the equation y = +4.80 mL/min + 0.92x (r = 0.97). The single-injection inulin clearance determination can detect a decrease of glomerular filtration rate at the beginning of kidney damage, given that our study included subjects with glomerular filtration rates greater than 35 mL/min. We conclude that the glomerular filtration rate can be determined by analyzing only two blood samples after a bolus injection of inulin.
Plasma Methadone Measurements and Their Role in Methadone Detoxification Programs
Authors: Wolff K , Hay A W , Raistrick D
Published: January 2020

We monitored eight patients who were receiving a decreasing dose of methadone for treatment for opioid addiction (detoxification). Patients with plasma concentrations of methadone less than 0.05 mg/L experienced withdrawal symptoms, relapsed, and re-abused illicit drugs. Four patients took extra methadone (illicitly obtained) during detoxification. None of the eight patients in our study were successfully weaned off methadone: all left the methadone detoxification program before the completion of treatment. Two patients subsequently returned to a fixed methadone program elsewhere, and four relapsed and returned to illicit drug misuse. Plasma measurements may help clinicians assess patients during methadone detoxification.
High Incidence of Significant Urinary Ascorbic Acid Concentrations in a West Coast Population—Implications for Routine Urinalysis
Authors: Brigden M L , Edgell D , McPherson M , Leadbeater A , Hoag G
Published: January 2020

Examination of 4379 routine urinalysis specimens with dipsticks sensitive to ascorbic acid showed that 22.8% were positive specimens. The mean urinary vitamin C concentration in this population was 2120 mumol/L. There was a high rate of false-negative dipstick results for hemoglobin in patients with vitamin C in the urine. The highest false-negative rates were observed in urine samples containing less than 50 erythrocytes per high-power field. In further experiments when volunteers consumed supplemental oral USP vitamin C at doses of 100, 250, 500, and 1000 mg or vitamin C-containing fruit juices, even the lowest doses of oral vitamin C or juice resulted in sufficient urinary vitamin C to produce false-negative dipstick results in hemoglobin and glucose testing. To prevent potentially dangerous false-negative results, screening urinalysis protocols relying only on dipstick testing should include a check for urinary vitamin C or use a dipstick that is not subject to vitamin C interference.
Are Clinical Laboratory Proficiency Tests as good as They Can Be?
Authors: Tietz N W , Rodgerson D O , Laessig R H
Published: January 2020

Present proficiency test services that use the peer group mean and statistically derived ranges of acceptability are not serving us optimally and are even counterproductive in some respects. We recommend that the target value be determined by a widely accepted reference method and that acceptable ranges be based on criteria related to clinical need. This approach was adopted several years ago in Germany and has already eliminated the use of several unsatisfactory analytical methods. Because the transition would probably take many years, we propose an interim solution to allow instrument manufacturers and laboratorians to adapt to these changes. The current peer group means and acceptable ranges should be supplemented by reference method values and acceptable ranges, based on clinical need, so that manufacturers and laboratorians can judge their performance against these new criteria and make the necessary adjustment in instrumentation and methodology. These processes should be paralleled by efforts to produce proficiency test materials that will not exhibit the matrix problems of present-day preparations.
Evaluation of the Rigor and Appropriateness of CLIA '88 Toxicology Proficiency Testing Standards
Authors: Jenny R W , Jackson K Y
Published: January 2020

The proposed rule for the Clinical Laboratory Improvement Amendments of 1988 (CLIA '88) describes uniform standards for the design of proficiency testing (PT) challenges and for the evaluation of laboratory performance. Successful performance on PT is a condition for laboratory certification by the federal Department of Health and Human Services. We conducted a retrospective evaluation of PT data collected from laboratories participating in the New York State therapeutic substance monitoring/quantitative toxicology PT program to determine how well laboratories performed by proposed PT standards. We found that the unsuccessful performance rate is very low (less than 0.4%) and that laboratories providing limited services are more susceptible to program sanctions than are full-service laboratories. The performance criteria are empirically fixed limits that are not consistent with either the state of practice or the analytical goals based on clinical requirements for good patient care. We suggest that the performance standards, if adopted, would be a weak challenge to the capability of today's therapeutic drug monitoring service and will not provide the impetus to bring analytical performance characteristics into full compliance with analytical goals.
Diagnosis of α-Mannosidosis by Measuring α-Mannosidase in Plasma
Authors: Prence E M , Natowicz M R
Published: January 2020

alpha-Mannosidosis is a lysosomal storage disease resulting from a deficiency of lysosomal alpha-mannosidase activity. Diagnosis of alpha-mannosidosis has traditionally been accomplished by demonstrating reduced alpha-mannosidase activity in leukocytes. We describe a new assay of alpha-mannosidase in serum or plasma that allows specific detection of the enzyme deficiency in alpha-mannosidosis with small, easily obtained sample volumes. The assay utilizes 40 microL of serum or plasma and a fluorescent substrate, 4-methylumbelliferyl-alpha-D-mannopyranoside in sodium acetate buffer, pH 4.0. The mean activity of a control population was 194 (SD 67) mU/L, whereas the activities obtained for four alpha-mannosidosis patients were 0, 17, 17, and 33 mU/L. Comparison with the standard leukocyte alpha-mannosidase assay showed this serum or plasma assay to be equally effective in diagnosing alpha-mannosidosis.
Enzymatic Assay of Inorganic Phosphate with Use of Sucrose Phosphorylase and Phosphoglucomutase
Authors: Tedokon M , Suzuki K , Kayamori Y , Fujita S , Katayama Y
Published: January 2020

We developed a new enzymatic method for the assay of inorganic phosphate (Pi) by using sucrose phosphorylase (SP; EC 2.4.1.7) and phosphoglucomutase (PGM; EC 5.4.2.2). Pi is transferred to sucrose by SP, producing alpha-D-glucose 1-phosphate (G1P) and alpha-D-fructose. G1P is transphosphorylated by PGM in the presence of alpha-D-glucose 1,6-bisphosphate to form alpha-D-glucose 6-phosphate, which is oxidized by NAD+ and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) to form 6-phosphogluconate (6PG) and NADH. Finally, the oxidation of 6PG by NAD+, catalyzed by 6-phosphogluconic dehydrogenase (EC 1.1.1.44), yields D-ribulose 5-phosphate and NADH. Thus two molecules of NADH are formed for each molecule of Pi, and the reaction is monitored at 340 nm. The Km values of SP for Pi and sucrose were 4.44 and 5.31 mmol/L, respectively. The best buffer was 1,4-piperazinediethanesulfonic acid (PIPES) at 50 mmol/L and pH 6-7. Implementing this method with a Cobas-Bio centrifugal analyzer allowed us to measure Pi accurately and precisely.
New Chromogen for Assay of Glucose in Serum
Authors: Reljic R , Ries M , Anić N , Ries B
Published: January 2020

We describe a colorimetric assay for glucose determination in human serum, with use of the chromogen 2-amino-4-hydroxybenzenesulfonic acid (AHBS), glucose oxidase, and peroxidase. With this assay, glucose concentrations less than or equal to 27.8 mmol/L can be measured in serum, with a sample/reagent volume ratio as low as 0.0025. The chromogen itself is easily soluble in water and does not require other components for the color change, making the reagent composition less complex. A single working reagent is used, and the reaction is completed within 10 min at 37 degrees C. The absorbance of the yellow reaction product is measured at 415 nm, and a blank sample measurement is not needed. The average analytical recovery of glucose in different human sera was 97.6%, with no significant interference of reducing compounds in serum. The results of the recommended procedure correlated well with those of the phenol/4-aminoantipyrine method of Trinder.
Pediatric and Perinatal Reference Intervals for Immunoglobulin Light Chains Kappa and Lambda
Authors: Herkner K R , Salzer H , Böck A , Mühl A , Tsaka T , Steger H , Pollak A , Schatten C , Popp W , Huber-Spitzy V
Published: January 2020

In routine analysis for immunoglobulin light chains in pediatric diagnostics, the age-related reference intervals for serum kappa (kappa) and lambda (lambda) light chains were evaluated in 1543 healthy subjects (newborns to age 16 years, including 168 premature infants). Light-chain analysis was performed by rate nephelometry. IgG, IgA, and IgM were measured simultaneously, and heavy- and light-chain differences were calculated for control purposes. Results for IgG, IgA, and IgM generally agreed with reference intervals reported in the literature. kappa showed age-related changes comparable with changes in IgG concentrations, whereas lambda showed moderate fluctuations. The kappa/lambda ratio showed an almost linear increase with age, starting with 0.97 at four months and reaching the highest value of 2.21 at 15 years (mean values). Preterm infants presented with markedly low serum concentrations of IgG and corresponding light chains but with adult-type kappa/lambda ratios because of the maternal-origin IgG.
Complexation of Iron with the Orally Active Decorporation Drug L1 (3-Hydroxy-1,2-Dimethyl-4-Pyridinone)
Authors: Kline M A , Orvig C
Published: January 2020

The stability constants for the Fe(III) complexes of the orally active iron decorporation drug L1 (3-hydroxy-1,2-dimethyl-4-pyridinone) have been determined by potentiometric titration [glass electrode, 25.0 degrees C, mu = 0.15 mol/L (isotonic) NaCl]. A simple computer model of blood plasma (citrate 100 mumol/L, transferrin 37 mumol/L) has been used to compare the Fe(III) binding efficacies in blood of L1 and the clinically used intravenously administered chelating agent deferoxamine.
Normal Variation of Plasma Lipoproteins: Postural Effects on Plasma Concentrations of Lipids, Lipoproteins, and Apolipoproteins
Authors: Miller M , Bachorik P S , Cloey T A
Published: January 2020

We examined the effects of postural change on the concentrations of plasma cholesterol, triglyceride, high-density lipoprotein (HDL) cholesterol, apolipoproteins (apo) A-I and B, and lipoprotein(a) [Lp(a)] in six volunteers who fasted 12 h before blood sampling. Baseline samples were drawn in the standing position; the subjects then assumed the supine or sitting position, and additional blood samples were drawn at intervals up to 40 min. They then returned to the standing position and were again sampled at intervals up to 40 min. In the supine position, lipid, lipoprotein, and apolipoprotein concentrations decreased rapidly within the first 5 min and stabilized after 20 min. Total and HDL cholesterol, apoA-I, apoB, and Lp(a) decreased by as much as 7-12% in the supine position and returned to baseline values 20-40 min after the standing position was resumed. Smaller changes (5-9%) were observed when the subjects were sitting, and returned to baseline within 20 min after the subjects resumed the standing position. The decrease in triglycerides was 17% in the supine position and 10-11% in the sitting position. Lp(a) concentrations decreased 7-8% in either the supine or sitting position and returned to baseline more slowly than did the other components. For all components the changes were most rapid within the first 10 min after changing posture.
Rapid Immunometric Measurement of C-Reactive Protein in Whole Blood
Authors: Urdal P , Borch S M , Landaas S , Krutnes M B , Gogstad G O , Hjortdahl P
Published: January 2020

We examined an instrument-free test for C-reactive protein (CRP) in whole blood. The NycoCard CRP Whole Blood test uses a cell-solubilizing dilution liquid, a membrane-bound antibody that binds CRP, and a gold-conjugated antibody for making visible the bound CRP. We obtained essentially identical dose-response curves in citrate-, heparin-, and EDTA-treated blood. CVs were 6.7-12.5% within series and 10.1-14.7% between series. The detection limit was 12 mg/L. Intralipid added to blood increased measured CRP by 10-20%, whereas no change was seen with added bilirubin, added serum amyloid P component, or the presence of rheumatoid factor. In 234 patients' blood samples the results of the NycoCard Whole Blood test correlated well (r = 0.96) with those of a turbidimetric serum method. The test allows reliable measurement of CRP from a small volume of whole blood (25 microL) without using expensive equipment; it should be useful for decentralized testing in hospital departments, emergency units, and primary health care centers.
Proficiency Testing from a Total Quality Management Perspective
Authors: Castañeda-Méndez K
Published: January 2020

Public concern over increasing health-care costs plus dramatized testing errors, has resulted in CLIA '88 with its more stringent rules governing laboratory performance. The purpose of the 1990 U.S. Health Care Financing Administration Final Rules for Proficiency Tests is to separate the quality laboratory from the poorly performing one. From the perspective of total quality management, the customer (patient) defines quality as virtually error-free test results. The current proficiency testing format defeats this. Its effective purpose is not to identify quality laboratories but to shut down the most prolific laboratories--regardless of their quality. There are two reasons for this. First, the proficiency testing format is incomplete: it is missing a minimum frequency criterion. Second, the data for determining the quality of a laboratory's performance (the degree of error-free results) are not being used. I propose a solution based on continuous improvement that promotes voluntarism, favors the quality laboratory, and reduces federal regulation.
Reference Intervals for Eight Modified Nucleosides in Serum in a Healthy Population from Italy and the United States
Authors: Pane F , Oriani G , Kuo K C , Gehrke C W , Salvatore F , Sacchetti L
Published: January 2020

We used a recently devised HPLC method to quantify eight modified nucleosides, an emerging group of tumor markers, in human serum and then calculated their reference intervals in a healthy population from Italy and the United States. We used the statistical procedure of element analysis, which reveals the effects of chosen variables (in this case, nationality, sex, and age) on an analyte (here, modified nucleosides). Using element analysis, we calculated the exact weight of each variable on the reference values. We found that nationality has the greatest effect on the serum concentrations of all the modified nucleosides apart from pseudouridine, whereas sex significantly influences only the concentrations of 4-pyridone-3-carboxamide-N1-ribofuranoside, 1-methylinosine and N2,N2-dimethylguanosine; age affects only N2,N2-dimethylguanosine. Thus, the reference intervals of all the nucleosides except pseudouridine were calculated separately for Italians and Americans, and the reference values for 4-pyridone-3-carboxamide-N1-ribofuranoside, 1-methylinosine, and N2,N2-dimethylguanosine were calculated separately for men and women. Our data form the baseline for study of variations in serum concentrations of modified nucleosides in various pathophysiological conditions.
Comparison of Methods for Measuring Free Thyroxin in Nonthyroidal Illness
Authors: Wong T K , Pekary A E , Hoo G S , Bradley M E , Hershman J M
Published: January 2020

Patients with severe nonthyroidal illness (NTI) often have decreased serum thyroxin (T4) concentrations and sometimes have decreased free T4 (FT4) and increased tumor necrosis factor-alpha (TNF-alpha) concentrations. We evaluated four commercial methods for measuring FT4 [Abbott IMx, Amersham Amerlex MAB, Nichols, and Diagnostic Products Corporation (DPC) RIA] and one method for TNF-alpha in 41 NTI patients, 24 euthyroid control subjects, and 10 hypothyroid patients. Free T4 index (FTI) was also measured by the Abbott IMx method. Euthyroid subjects results were in the stated normal ranges. NTI FT4 was subnormal in 2.4%, 61%, and 29% by the Nichols, DPC, and Amerlex methods, respectively. The DPC, Amersham Amerlex, and Abbott IMx methods gave significantly lower FT4 values for the NTI group than for the controls. There were good correlations between the various FT4 methods in the NTI group. FTI concentrations correlated well with FT4 for the euthyroid and hypothyroid groups but poorly for the NTI group. The Abbott IMx and Nichols RIA methods yield values in the hypothyroid range for only a small proportion of NTI patients.
Quantification of Islet Cell Antibodies by Microscope Photometry and Antibody Titration Compared
Authors: Bright G M
Published: January 2020

Islet cell antibodies can predict eventual insulin-dependent diabetes mellitus. In the standard method used by the Immunology of Diabetes Workshop (IDW), predictive power depends on antibody titer as determined by testing multiple serum dilutions. Here I report use of a microscope-based photometry system (MPS) to test whether islet fluorescence intensities from undiluted sera can predict IDW results. MPS testing of 120 undiluted IDW specimens correctly identified 27 of 31 positive and 84 of 89 negative specimens. The relationship between IDW consensus values and MPS readings of undiluted sera is: IDW = 2.45 MPS - 1.44 (r = 0.67, P less than 0.001). Thus, corrected islet intensities from undiluted sera correlated well with IDW values. However, the ability of MPS to predict high IDW consensus values is limited, which may reflect the variable antigenic content of pancreas specimens; moreover, background correction as currently applied is incomplete; nonspecific immunofluorescence appears to emanate from within the islet.
Ultrasensitive Radioimmunoassay of Prostate-Specific Antigen
Authors: Graves H C , Wehner N , Stamey T A
Published: January 2020

We describe a modification of the Yang Pros-check radioimmunoassay for prostate-specific antigen (PSA) that increases the analytical sensitivity of the assay approximately threefold (from a working range of 0.3-50 to 0.1-1.2 micrograms/L). It can detect PSA added to zero-concentration diluent (bovine serum albumin solution) at 0.10 microgram/L or added to zero-concentration control female serum at 0.20 microgram/L (P less than 0.05). In 26 patients tested after cystoprostatectomy for bladder cancer (who had normal prostates without cancer on histologic examination), PSA values by this ultrasensitive assay were all less than 0.10 microgram/L. Therefore, we propose this value as the upper limit of the 95% reference interval. In a retrospective study of two patients who developed recurrent prostate cancer, serum PSA values increased above the 0.1 microgram/L detection limit 175 and 581 days before increasing above the 0.3 microgram/L detection limit of the standard Yang assay. This ultrasensitive radioimmunoassay of PSA should prove more useful than current methods for detecting early recurrence of prostate cancer.
Assay of Urinary Free Fucose by Fluorescence Labeling and High-Performance Liquid Chromatography
Authors: Suzuki J , Kondo A , Kato I , Hase S , Ikenaka T
Published: January 2020

The concentrations of free fucose and other sugars in urine of cancer patients and healthy subjects were analyzed by high-performance liquid chromatography. After the urine samples were dried, we coupled the sugars in the residue with 2-aminopyridine to be detected as fluorescent derivatives. We then analyzed the pyridylamino derivatives of the sugars with an anion-exchange column and borate buffer. The difference between cancer patients and healthy subjects for the mean concentrations of fucose corrected for creatinine was significant (P less than 0.001). We checked the relationship between the concentrations of other sugars and the presence of cancer. This method is highly sensitive, and neither a cleanup procedure before labeling nor purification before injection into the column is needed. Not only fucose but also other sugars can be detected simultaneously, so this method should be useful for studying any changes in sugars in urine in various diseases.
Nonisotopic Binding Assay for Measuring Vitamin B12 and Folate in Serum
Authors: van der Weide J , Homan H C , Cozijnsen-van Rheenen E , Vivié-Kipp Y , Poortman J , Kraaijenhagen R J
Published: January 2020

We evaluated a nonisotopic method (CEDIA; cloned enzyme donor immunoassay) for estimating vitamin B12 and folate in serum. The assays were performed with a Cobas-Mira analyzer. Intra-assay CVs were from 3.7% to 11.0% for vitamin B12 and from 1.2% to 10.7% for folate. Interassay CVs ranged from 9.5% to 11.9% for vitamin B12 and from 6.1% to 18.5% for folate. Linearity was satisfactory, with analytical recovery of 94% at 8.7 and 25.4 nmol/L for folate and 280 and 554 pmol/L for vitamin B12. The detection limit was 3.6 nmol/L for folate and 12.3 pmol/L for vitamin B12. Results of this assay correlated well with those of a conventional radioassay: r = 0.98 for vitamin B12 (n = 51) and r = 0.97 for folate (n = 57). The CEDIA was easy to perform but appeared to be unreliable for use with samples from myeloma patients.
Establishment of an External Quality-Assessment Scheme for Amino Acid Analyses: Results from Assays of Samples Distributed during Two Years
Authors: Rattenbury J M , Tewnsend J C
Published: January 2020

Vol. 36

p. 224: In the caption for Figure 1, the curves should be identified as follows: A, *; B, +; and C, •.

p. 371: Left column, line 10, should refer to women, not men. Right column, third line above the Statistics section, should note that results were read at 450 nm (with a reference wavelength of 630 nm). In Table 2, INN prefix refers to Innsbruck monoclonal antibodies.

p. 373: Right column, line 9, should read: however, only the hCG/free-α ratio was significantly different between progressive and nonprogressive tumors (P<0.05). The Figure 5 subcaption, first sentence, should read: Serum concentrations exceeding the physiological ranges of the three markers (mean serum values for healthy men plus 3 SD; 99.7% confidence interval) were defined as positive for those markers.

p. 374: Right column, line 12, should read: suppression of free-α secretion by an LHRH antagonist.
Measuring Urinary Glycosaminoglycans in the Presence of Protein: An Improved Screening Procedure for Mucopolysaccharidoses Based on Dimethylmethylene Blue
Authors: de Jong J G , Wevers R A , Liebrand-van Sambeek R
Published: January 2020

Earlier we described a simple and reliable screening procedure in urine for mucopolysaccharidoses based on the color reaction of glycosaminoglycans (GAGs) with dimethylmethylene blue. At physiological concentrations of urinary protein, we observed an obvious interference by protein in the assay. By modifying the assay, we abolished the protein interference. The modified procedure is not disturbed by human serum albumin, IgG (both tested with as much as 5 g/L of protein), or urinary proteins. The modified procedure appeared as reliable as the original. No false-negative results were found in a series of 26 urine samples from patients with mucopolysaccharidoses (sensitivity 100%). In a series of 405 urine samples offered for metabolic screening, 24 samples with increased GAG content and normal GAG composition were seen (specificity 94%). The method may also be applicable for determining GAG in other body fluids or solutions containing protein.
Effects of Albumin and Immunoglobulin A on Fructosamine Assay
Authors: Singh J , Kulig K A
Published: January 2020

Serum fructosamine, albumin, and IgA were measured in three groups of human subjects: 54 nondiabetic normal individuals, 149 nondiabetic patients, and 149 diabetic patients. Normal subjects had significantly (P less than 0.05) higher fructosamine (2.91, SD 0.33, mmol/L) than did nondiabetic patients (2.49, SD 0.46, mmol/L). Each of these groups had significantly (P less than 0.05) lower fructosamine than did diabetic patients (3.76, SD 1.16, mmol/L). Increased fructosamine appeared to be associated with increases in both albumin and IgA. However, fructosamine was significantly (P less than 0.05) correlated with neither albumin nor IgA in the normal group, with only albumin in the nondiabetic group, but with both albumin and IgA in the diabetic group. Selective combinations of these populations not only shifted these significances but also eliminated some of the correlations. Our results suggest caution regarding the diagnostic role and universality of fructosamine and of its correlation with IgA as indicated by others.
Biological Variability of Lipoproteins and Apolipoproteins in Patients Referred to a Lipid Clinic
Authors: Kafonek S D , Derby C A , Bachorik P S
Published: January 2020

We determined the physiological variability of total cholesterol, high- (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, and apolipoproteins A-I and B in fasting blood samples from patients referred to the Johns Hopkins Lipid Referral Clinic. Samples were taken on each of three occasions during baseline evaluation visits before the patients were treated. The median physiological coefficients of variation (CVp) were as follows: total cholesterol, 5.0%; triglycerides, 17.8%; HDL cholesterol, 7.1%; LDL cholesterol, calculated from the previous three measurements, 7.8%; and apolipoproteins A-I and B, 7.1% and 6.4%, respectively. There were no significant differences in CVp between children (less than or equal to 18 years) and adults (greater than 18 years) for any of the measurements. On the basis of our findings, single measurements in serial samples taken on three occasions suffice to establish the patients' usual values with the following precisions (+/- 1 CV): total cholesterol, +/- 4%; triglycerides, +/- 11%; HDL cholesterol, +/- 8%; LDL cholesterol, +/- 6%; and apolipoproteins A-I and B, +/- 7%.