bluuebunny/crossref_metadata_2025 huggingface dataset:
Homogeneous time-resolved fluoroimmunoassay of thyroxin in serum.
Authors: Hemmilä I , Malminen O , Mikola H , Lövgren T
Published: January 2020

We describe a rapid, simple nonseparation fluoroimmunoassay for determination of thyroxin in serum. The assay is based on the labeling of thyroxin directly with a fluorescent europium chelate, the fluorescence of which is quenched on binding to an antithyroxin antibody. With the assay buffer we used, maximum quenching is 90%. The rapid achievement of equilibrium in the assay solution, regardless of the sequence of reagent additions, allows fast measurement of thyroxin. Precision was good (CV less than 5%) within the clinical range for total thyroxin (50-300 nmol/L), and results correlated well with those by a commercial radioimmunoassay.
Determination of D-sorbitol in human erythrocytes by an improved enzymatic method with fluorometric detection.
Authors: Liao J C , Rountree M , Good R , Hook J , Punko C
Published: January 2020

In this enzymatic method to analyze erythrocytes for D-sorbitol, the erythrocytes were separated from plasma by centrifugation, washed with isotonic saline (9 g/L NaCl), then diluted threefold with more saline. We lysed 1.5 mL of the diluted erythrocytes with chloroform and precipitated the protein with 58 g/L HClO4 solution. The resulting supernates were mixed with buffer, NAD+, and sorbitol dehydrogenase (EC 1.1.1.14). For standards, we added sorbitol to the erythrocytes before lysing. After 25 min of incubation at 37 degrees C, the fluorescence responses were recorded. Results for sorbitol were corrected for sample-blank and enzyme fluorescence, and were then normalized for hemoglobin content. Response was linear for a sorbitol concentration range of 1 to 30 mumol/L. Reproducibility was good, with an average CV of 2.5% at 10 mumol/L. Results for healthy individuals and diabetic patients are presented.
Evaluation of the Technicon Chem-1.
Authors: Barlow I M , Harrison S P , Hogg G L
Published: January 2020

We evaluated the performance of 15 colorimetric and three ion-selective electrode assays in the Technicon Chem-1 serum analyzer and briefly assessed the suitability of plasma and urine for analysis in the system. Within- and between-batch precision, accuracy, correlation, and linearity of all methods was acceptable but some assays, notably those for bicarbonate and creatinine, were susceptible to interferences. Except for the total bilirubin and lactate dehydrogenase assays, plasma can be assayed successfully in the instrument. Urine samples can also be assayed but specimens for phosphate analysis must be diluted in a polyvinylpyrrolidone solution before analysis, and the calcium method is sensitive to variations in urinary pH.
A simple liquid-chromatographic method applied to determine caffeine in plasma and tissues.
Authors: Biaggioni I , Paul S , Robertson D
Published: January 2020

In this simple, reliable assay for quantifying caffeine in plasma and tissues, methylxanthines are first partly purified from plasma and acid extracts of tissue by passage through solid-phase columns. The ease of this extraction method permits a relatively large number of samples to be processed daily. Quantification is by reversed-phase high-pressure liquid chromatography (mobile phase: acetic acid/acetonitrile/water, 2/6/92 by vol). Caffeine is eluted in 20 min. The reliability of this method allows its automation. This method has been adapted to measure caffeine in brain and kidney extracts and in as little as 10 microL of plasma. After 10 days of oral administration of caffeine (1 g/L, in drinking water) to six rats, the mean (+/- SEM) concentrations of caffeine in plasma, brain, and kidney were 18.6 +/- 6.0 micrograms/mL, 16.2 +/- 1.5 micrograms/g, and 18.9 +/- 2.0 micrograms/g, respectively. Correlations were linear between concentrations of caffeine in plasma and brain (r = 0.86) and between concentrations in plasma and kidney (r = 0.91). This method should be useful in studying the effects and mechanisms of actions of methylxanthines.
Libyan family with beta-thalassemia trait associated with hypercholesterolemia with widespread xanthomas.
Authors: Sheriff D S , el Fakhri M
Published: January 2020

We describe a Libyan family with beta-thalassemia trait associated with unusually high concentrations of hemoglobin A2 and hypercholesterolemia. The family consists of the father, mother, and three sons. The marriage was consanguineous. The concentrations of total cholesterol and low-density lipoprotein cholesterol in serum were very high in two sons who also had widespread xanthomas. The erythrocyte membranes showed a high cholesterol/phospholipid ratio, with no significant susceptibility to lipid peroxidation in vitro.
Free triiodothyronine measured in dried blood spots from normal, low-birth-weight, and hypothyroid neonates.
Authors: Laroche D , Lemonnier F , Viel J F , Travert G , Fernandez Y
Published: January 2020

Free triiodothyronine (FT3) has rarely been studied in neonates, primarily because of obvious problems in obtaining serum samples from neonates for research purposes. We adapted an analog radioimmunoassay for measuring FT3 in dried blood samples and used it to assay 361 samples selected from those collected for the screening for neonatal hypothyroidism. The mean FT3 concentration in healthy neonates on the fourth postpartum day is 2.55 pmol per liter of whole blood (SD 0.78 pmol/L, n = 145), the same as in healthy adults. Low-birth-weight infants have a decreased concentration of FT3, and this decrease is much greater in premature neonates than in infants at low weight for gestational age. In six hypothyroid newborns, the FT3 concentration was normal or increased, clearly indicating that FT3 assay is not a diagnostic tool for hypothyroidism. FT3 was barely detectable in one case of congenital galactosemia.
An enzyme immunoassay procedure for cancer antigen 125 evaluated.
Authors: Ryder K W , Oei T O , Hull M T , Sample M M
Published: January 2020

The performance of a new enzyme immunoassay (EIA) procedure (Abbott Labs.) for cancer antigen 125 (CA 125) met or exceeded the manufacturer's claims for all analytical variables examined. Overall correlation with results obtained with a radioimmunoassay (RIA) were good. However, near the decision thresholds typically chosen to define a positive result for ovarian carcinoma, EIA results were 10 to 20 arbitrary units/mL less than the RIA results. At specific decision thresholds, therefore, the sensitivities and specificities of the EIA and RIA procedure differed. Adjusting the decision thresholds gave a similar optimum efficiency for each procedure: EIA, 82.9% (decision threshold, 35 units/mL); RIA, 83.4% (decision threshold, 54 units/mL). Receiver-operating characteristic curves showed that the two procedures' ability to distinguish patients with active ovarian carcinoma from those with disease in remission was the same.
Reflotron cholesterol measurement evaluated as a screening technique.
Authors: Sedor F A , Holleman C M , Heyden S , Schneider K A
Published: January 2020

We evaluated the analytical performance of Boehringer Mannheim Diagnostics' "Reflotron" analyzer for the measurement of cholesterol. Coefficients of variation (CVs) for whole-blood cholesterol were: within-day 2.0% and 2.2% at 1680 and 2670 mg/L, respectively; between-day 1.8% and 2.4% (n = 9 and 8). Results were similar for serum and heparinized or EDTA-treated single-donor plasma (CV 1.4% to 2.6%). CVs of results for two reconstituted commercial quality-control materials were 3.4% and 4.6%. Heparin and hematocrit were evaluated as interferents, and critical limits for interference were identified for bilirubin, hemoglobin, and triglyceride in blood and plasma or serum. When sample collection and analysis were controlled by trained personnel, results with the Reflotron (y) compared well with those by the Ektachem procedure (x) for both blood and serum samples: r = 0.950, y = 0.944x + 130 mg/L; and r = 0.955, y = 0.93x + 43.5 mg/L, respectively. The same comparability was observed when the analysis was performed by briefly trained high-school students: r = 0.980, y = 0.949x + 23 mg/L. Performance decreased when both collection and analysis were performed by laymen: r = 0.880, y = 0.870x + 186 mg/L.
Stability of serum fructosamine during storage.
Authors: Koskinen P , Irjala K
Published: January 2020

Stability of serum fructosamine during storage was evaluated in serum specimens obtained from 27 diabetic individuals. The samples were divided into six aliquots, which were stored at -20 degrees C and -70 degrees C for two, eight, and 16 months. The minor systematic differences between the six treatments contrasted with the considerable variation of individual specimens. The mean percentage changes in the six treatments ranged between -4.6% and 7.5%, whereas the changes in individual specimens ranged from -20% to 26.7%. Several factors evidently contribute to this variation, one being progressive in vitro glycation, especially at -20 degrees C. Small changes in fructosamine concentrations between consecutively drawn specimens, determined after storage, evidently should be interpreted cautiously. Low temperatures, at least -70 degrees C, are preferable to minimize pre-analytical variation during storage.
Definitive liquid-chromatographic demonstration that N-ethylglycine is the metabolite of lidocaine that interferes in the Kodak sarcosine oxidase-coupled method for creatinine.
Authors: Roberts R T , Alexander N M , Kelner M J
Published: January 2020

Patients receiving lidocaine may show false increases of serum creatinine as assayed by the single-slide method on the Kodak Ektachem 700. Bissell et al. (Clin Chem 1987;33:951) suggested that this interference was due to oxidation of N-ethylglycine (NEG), a previously uncharacterized metabolite of lidocaine, by the sarcosine oxidase preparation used in the Ektachem creatinine slide. To investigate this possibility, we synthesized NEG, added it to drug-free human serum, and analyzed the NEG-supplemented sera for creatinine with the Ektachem 700. We found the following linear relationships between creatinine bias (y, mg/L) and NEG concentration (x, mg/L) for first (I), third (III), and fourth (IV) generation slides: I: y = 1.70x - 0.8 mg/L (n = 13, r = 1.0) III: y = 0.39x - 0.3 mg/L (n = 3, r = 1.0) IV: y = 0.79x - 1.8 mg/L (n = 13, r = 1.0) Using HPLC, we directly demonstrated the presence of NEG in sera of patients receiving lidocaine and quantified NEG concentrations in sera from four of these patients. The increasing artifactual bias in creatinine with increasing NEG concentration unequivocally confirmed that NEG is responsible for the lidocaine-associated interference in the Kodak Ektachem single-slide creatinine method.
Concentrations of serotonin in plasma--a test for appendicitis?
Authors: Singh S M , Dean H G , de Dombal F T , Wilson D H , Flowers M W
Published: January 2020

We assessed the value of measuring serotonin (5-hydroxytryptamine) in plasma (by HPLC) in the diagnosis of acute appendicitis. Values for patients with subsequently confirmed appendicitis (11-145 nmol/L, median 70 nmol/L) significantly (P congruent to 0.005) exceeded those for patients with abdominal pain in whom appendicitis was only a possible diagnosis (2-45 nmol/L, median 20 nmol/L). The results for appendicitis patients were bimodally distributed, with low results found in patients where surgery revealed gangrenous appendicitis with little viable appendicular tissue. We conclude that measuring serotonin may be of value in confirming or excluding the diagnosis of early acute appendicitis where the physical signs are equivocal, and thus helps reduce unnecessary appendectomies. However, serotonin is of little help in diagnosing gangrenous appendicitis, where physical signs are more likely to be clearcut.
Escape from blockade of interfering heterophile antibodies in a two-site immunoradiometric assay for thyrotropin.
Authors: Zweig M H , Csako G , Spero M
Published: January 2020

Sandwich-type immunoassays in which mouse monoclonal antibodies are used are subject to positive interference by heterophile antibodies present in human serum. Manufacturers now customarily add nonspecific mouse immunoglobulins to absorb the heterophile antibodies and eliminate such interference. We describe the case of a patient who had spurious increases in thyrotropin concentration in serum despite use of the mouse immunoglobulins included in the assay kit. This resulted in a puzzling clinical picture, a workup, and treatment. We demonstrate that the observed increases in thyrotropin were markedly reduced by including additional amounts of mouse immunoglobulins of the appropriate class, subclass, and fragment type in the assay mixture.
Lactulose interferes in the alkaline picrate assay for creatinine.
Authors: Bruns D E
Published: January 2020

Errors of more than 10 mg/L in measured serum creatinine concentrations were encountered for an azotemic patient who was given lactulose orally. The magnitude of the apparent error fluctuated with the dose of lactulose. Additions of lactulose to serum produced a linear increase in the creatinine measured by each of two automated methods that involve use of the alkaline picrate (Jaffé) reaction. A lactulose concentration of 100 g/L produced positive interferences of 30 and 65 mg/L in kinetic (Beckman Astra) and continuous-flow (Technicon SMAC) assays, respectively, but caused no problem in an enzymatic assay for creatinine. The results of creatinine assays must be interpreted with caution in patients treated with lactulose.
Use of alternative rules (other than the 1(2)s) for evaluating interlaboratory performance data.
Authors: Ehrmeyer S S , Laessig R H , Schell K
Published: January 2020

Previous studies have documented the ineffectiveness of using either the group mean +/- 2 group standard deviations (SD) or the 1(2)s rule as the standard of acceptable performance in evaluating interlaboratory proficiency testing (PT) data. Using computer simulation of PT data, we evaluated the efficiency of 244 alternatives to the 1(2)s rule, all based on the PT population's mean and SD. Using the traditional interlaboratory PT format, we determined the ability of each rule to correctly identify both good and deficient intralaboratory performance. The rules are based on results from one to five PT samples "analyzed" at the same time. Because the effectiveness of the criteria set for acceptable performance in a PT program is influenced by the population SD, each rule's capabilities were examined for PT populations with interlaboratory SDs ranging from 1% through 10% of the population mean value. All rules achieve their maximum efficiency over a narrow range of interlaboratory SDs. For PT evaluations of intralaboratory performance to be optimally effective, selection of the rule must be based on the SD of the PT population.
Extrinsic-pathway enzyme-linked coagulation assay (EP-ELCA). A clot-based alternative to prothrombin time for measurement of extrinsic pathway factors in plasma.
Authors: Doellgast G J , Triscott M X , Buss D H , West J
Published: January 2020

This solid-phase colorimetric microtiter-plate clotting assay is much more sensitive than standard clotting tests. In enzyme-linked coagulation assay (ELCA), enzyme-labeled fibrinogen and solid-phase fibrinogen are the substrate for thrombin generated in the clotting cascade. We used this assay to measure the factors of the extrinsic pathway by an extrinsic pathway-specific assay (EP-ELCA) and to determine the individual factors of the extrinsic pathway (VII, X, V, II) in plasmas of coumadin-treated and heparin-treated patients, with prothrombin time (PT) values used as a reference. In the ELCA method, samples and controls are incubated on the same plate, eliminating the requirement for pre-standardization of the substrate "plasma" before the factor assay is done. Concentrations of factors are determined by serially diluting sample and control plasmas to yield equivalent activity at given dilutions, a more direct approach for measuring specific factors than determining log concentrations vs log clotting time. Changes in the concentrations of clotting factors are seen before changes are apparent by PT. For coumadin-treated patients, all vitamin K-dependent factors were significantly (P less than or equal to 0.001) less than in normal controls, whereas factor V concentrations were normal, as expected. For patients treated with heparin, concentrations of factors X and VII were less than in normal controls (P less than 0.01) and results for EP-ELCA, II, and V assays were normal. This methodology can readily be automated.
Serum fructosamine in diabetic pregnancy.
Authors: Frandsen E K , Sabagh T , Bacchus R A
Published: January 2020

Serum fructosamine was measured in 275 blood donors, in 559 subjects with a normal pregnancy, in 32 gestational diabetics being treated with insulin and 69 being treated by diet only, and in 53 pregnant subjects with established diabetes. In none of the pregnant subgroups did the mean fructosamine concentration exceed that of the donor group. The concentration in normal pregnant subjects showed a modest but significant decrease with gestational age and an increase with maternal age. Hyperglycemic non-pregnant subjects (n = 24) had significantly increased serum fructosamine concentrations, and 96% of these subjects exceeded the upper 95% confidence limit for fructosamine in the donor group. A highly significant correlation was demonstrated between serum fructosamine and preprandial plasma glucose in the hyperglycemic subjects. A weak, but significant, correlation was shown for the entire population sample of antenatal patients, while this was non-significant within each of the sub-groups comprising established diabetics and gestational diabetics, respectively.
Radioenzymatic assay of catecholamines in plasma after a preliminary solvent extraction compared with an analogous liquid-chromatographic method.
Authors: Feoli J , Bijault C , Dehennin L
Published: January 2020

Catechol-borate complexation and ion-pair formation combined with organic solvent extraction as preliminaries to radioenzymatic assay (REA) with catechol-O-methyltransferase-catalyzed methylation allows the quantification of catecholamines in plasma samples of any volume. We attained improved detection limits for 1-mL samples: 9 ng/L for norepinephrine (NE), 8 ng/L for epinephrine (E), and 11 ng/L for dopamine (DA). Precision data resemble those obtained by REA for small-volume samples. Comparison with a liquid chromatography-electrochemical detection (LCEC) technique showed the two methods to be equivalent for NE and E determinations, but DA estimations were lower by REA than by LCEC.
Improved receptor assay for measuring digoxin activity.
Authors: Bednarczyk B , Soldin S J , Gasinska I , D'Costa M , Perrot L
Published: January 2020

We describe a receptor assay of digoxin activity involving Na+/K+-ATPase (EC 3.6.1.37) derived from human heart tissue. The procedure requires 500 microL of serum or plasma and incorporates one purification step, with Sep-Pak C18 cartridges (Waters). The method appears to be considerably more specific for digoxin and its cardio-active metabolites than are conventional immunoassays. Cardio-inactive metabolites and several digoxin-like factors cross react only slightly. The between-day coefficient of variation for the procedure ranged from 8.10% to 1.37% for digoxin concentrations between 0.5 and 5.0 nmol/L.
Colorimetry of p-aminohippurate in the presence of sulfamethoxazole.
Authors: Preuss H G , Razavi M H , Slemmer D , Zein M
Published: January 2020

Colorimetric quantification of p-aminohippurate (PAH), which is helpful in assessment of renal function, is subject to interference from sulfa compounds such as sulfamethoxazole. We were unable to measure serum PAH in two patients receiving a trimethoprim-sulfamethoxazole combination because of interference by the latter with the colorimetric estimation. We found that isoamyl acetate removes sulfamethoxazole from the samples without influencing PAH. The extraction is simple, inexpensive, and reproducible.
Macroamylasemia with a markedly increased amylase clearance ratio in a patient with renal cell carcinoma.
Authors: Kazmierczak S C , Van Lente F , McHugh A M , Katzin W E
Published: January 2020

We report hyperamylasemia, macroamylasemia, and a markedly increased amylase clearance/creatinine clearance ratio in a patient with renal cell carcinoma. Serum amylase activity was characterized as macroamylase by gel exclusion chromatography. Electrophoretic separation revealed an atypical band of amylase, migrating anodal to the S2 control fraction. Electrophoresis of urine revealed the presence of both S1 and S2 fractions, but not the atypical band found in serum. Quantification of the salivary- and pancreatic-type amylase fractions showed amylase in urine to be 100% salivary. Immunofixation disclosed the macroamylase to consist of an immune complex between amylase and IgA-lambda antibody. Binding-capacity studies showed that the serum immunoglobulin was present in excess and could bind 46% and 49% additional S-type amylase activity derived from saliva and the patient's urine, respectively. The amylase clearance/creatinine clearance ratio was markedly supranormal (0.134), unexpected in a patient with macroamylasemia. A biopsy specimen of the renal cell tumor was found to contain significant salivary-type amylase activity. These results suggest production of amylase by tumor tissue in the renal carcinoma and secretion of S-type amylase into the patient's urine. Evidently, macroamylase should be confirmed by gel exclusion chromatography.
Simultaneous determination of catecholamines and serotonin by liquid chromatography, after treatment with boric acid gel.
Authors: Imai Y , Ito S , Maruta K , Fujita K
Published: January 2020

We describe a liquid-chromatographic method for simultaneously determining norepinephrine, epinephrine, dopamine, and serotonin in 0.5 mL of human plasma. These analytes are purified on boric acid gel from Aldrich, separated on a reversed-phase C18 column, and detected electrochemically at +600 mV. Absolute recoveries of internal standards were 84% for 3,4-dihydroxybenzylamine and 57% for N-methylserotonin. Reproducibility was good to excellent, depending on the concentration of the analytes. A chromatographic run is complete in 40 min, but this can be shortened by about half when the determination of only serotonin is required, by increasing the column temperature from 40 degrees C to 60 degrees C.
Measurement of cholesterol in serum by gas chromatography/mass spectrometry at moderate mass resolution, with a nonendogenous cholesterol isomer as internal standard.
Authors: Kinter M , Herold D A , Hundley J , Wills M R , Savory J
Published: January 2020

We describe a gas chromatography/mass spectrometry method for the quantitative analysis of cholesterol in serum. A structural isomer of cholesterol, 7,(5 alpha)-cholesten-3 beta-ol, is used as an internal standard, its primary advantage being its lesser cost relative to that of a stable-isotope-labeled analog. Analysis of the National Bureau of Standards Certified Reference Serum (SRM 909) was used to validate the method. The results show this method to be highly accurate (bias = -0.6%) and precise (CV = 1.6% between-run, 1.2% within-run). The performance of this method is, therefore, sufficiently good to allow its use as a reference method for determinations of cholesterol in serum.
Cis-4-decenoic acid in plasma: a characteristic metabolite in medium-chain acyl-CoA dehydrogenase deficiency.
Authors: Duran M , Bruinvis L , Ketting D , de Klerk J B , Wadman S K
Published: January 2020

The profile of organic acids in plasma of patients with a deficiency of medium-chain acyl-CoA dehydrogenase (EC 1.3.99.3) was determined by gas-liquid chromatography of trimethylsilylated derivatives of the acids isolated by ethyl acetate extraction. All 13 patients had increased concentrations of free octanoate, cis-4-decenoate, and decanoate in their plasma. Cis-4-decenoate, an intermediary metabolite of linoleic acid, is pathognomonic of medium-chain acyl-CoA dehydrogenase deficiency. This metabolite does not accumulate in plasma after oral loading with medium-chain triglycerides, in contrast to octanoate and decanoate. Two postmortem plasma samples from victims of infant sudden-death syndrome had detectable octanoate and decanoate, but cis-4-decenoate could not be detected. The identification of cis-4-decenoate in plasma may be an aid in the diagnosis of an inherited defect in oxidation of medium-chain fatty acids.
Changes in the concentration of testosterone in serum during the menstrual cycle, as determined by liquid chromatography.
Authors: Oka K , Hirano T , Noguchi M
Published: January 2020

We used a newly developed high-performance liquid chromatographic (HPLC) method to determine the concentration of testosterone in serum from women and compared the results with those obtained by conventional radioimmunoassay. We used a conventional silica gel column and organic solvent mixture (ethanol plus n-hexane containing a small amount of water). The detection limit for testosterone was as low as 0.2 micrograms/L, sufficient to correctly determine the concentration of the hormone in serum from women. For the calibration curve, we plotted the peak-height ratio of testosterone to 19-nortestosterone. The menstrual-cycle-related rhythm of the concentration of testosterone in serum was related to follicular and luteal phase-shifting, the concentration being considerably greater in the luteal phase than in the follicular phase. In contrast, RIA showed only minor and irregular fluctuation in the concentrations of the hormone throughout the menstrual cycle. When we used the HPLC to measure the hormonal change in a woman with an irregular menstrual cycle, we found that her testosterone concentration increased abnormally early after menstruation.
Immunoprecipitation method for CK-MB analysis re-evaluated: influence of CK-BB and macro-CK on blank activities.
Authors: Jacobs E , Anzalone T , Sarkozi L
Published: January 2020

We evaluated the analytical performance of the immunoprecipitation technique for quantification of creatine kinase (CK; EC 2.7.3.2) isoenzyme MB, focusing on specimens with increased blank activities. The samples we studied had blank values that were equal to or greater than either 15 U/L or the uncorrected CK-MB value. Of 134 specimens selected, 16 and 21 contained macro CK type 1 and CK-BB, respectively. All samples containing macro CK type 1 gave negative CK-MB values, even though four contained significant quantities of CK-MB. Correcting the blank value for the fluid displacement of the second antibody suspension eliminated all but three of the negative results. However, 45 specimens, negative for CK-MB by electrophoresis, gave CK-MB values ranging from 1 to 21 U/L. Furthermore, 11 of the specimens containing macro-CK type 1 were in this group. Thus, the presence of macro-CK type 1 definitely interferes with the immunoprecipitation technique. Our results indicate the need to re-evaluate the diagnostic accuracy of the immunoprecipitation technique, especially when the un-adjusted blank activities are increased.
Renal clearance of pancreatic and salivary amylase relative to creatinine clearance in patients with renal disease and proteinuria.
Authors: Wetzels J F , Hafkenscheid J C , Hessels M , Hoitsma A J , Koene R A
Published: January 2020

To study the charge-selective properties of the glomerular filter in renal disease, we measured the fractional clearance, relative to creatinine clearance (ECC), of the amylase isoenzymes pancreatic amylase and salivary amylase, which have identical size but different charge. In 63 healthy subjects the mean (and SD) fractional excretion of pancreatic amylase, 4.07% (1.24%), was fourfold that of salivary amylase: 1.02% (0.54%). For 29 patients with renal disease and proteinuria, the mean fractional excretion of pancreatic amylase was significantly lower, 3.31% (1.94%), and that of salivary amylase significantly higher, 2.06% (1.41%), than in controls. In these patients, fractional excretions of both these isoenzymes were negatively correlated with urinary excretion of beta 2-microglobulin and ECC. Evidently, differences in clearances of pancreatic and salivary amylase are a consequence of differences in charge-related glomerular filtration. The relative increase of salivary amylase clearance in patients with renal disease and proteinuria is most probably caused by a loss of the charge-selective properties of the glomerular basement membrane.
Legal issues related to drug testing in the clinical laboratory.
Authors: Chamberlain R T
Published: January 2020

As has been reported many times by the lay press, urine drug testing may pose some unique challenges. The clinical laboratory interested in industrial drug testing (typically known as employee drug testing) should be aware of the many challenges that may be brought on by the fact that the result may be contested in an adversarial proceeding. This is what makes the urine drug test a forensic test. It may be one piece of evidence or the only piece of evidence used in an adversarial proceeding that may decide on punitive or rehabilitative action against an employee. As a result, unique standards for governmental contract laboratories have been proposed from the National Institute on Drug Abuse, and special proficiency testing and accreditation procedures have been promoted by professional societies. These standards illustrate the sensitive nature of the results. Because the results are subject to adversarial proceedings, all parties concerned in the testing process should be aware of the legal issues surrounding urine drug testing. There are constitutional and statutory issues as well as tort issues such as negligence, defamation, invasion of privacy, battery, infliction of emotional distress, and others. Laboratories should be especially aware of these issues, since they may be brought in as a third-party defendant to a suit or brought in as a participant in gathering the evidence. The laboratory should also be aware of other legal ramifications such as chain of custody, expert testimony, and the acceptability of scientific evidence.
Total lactate dehydrogenase and its isoenzymes in serum of patients with non-small-cell lung cancer.
Authors: Rotenberg Z , Weinberger I , Sagie A , Fuchs J , Davidson E , Sperling O , Agmon J
Published: January 2020

Values for total lactate dehydrogenase (LD, EC 1.1.1.27) activity in serum and LD isoenzymes were determined at diagnosis in 273 patients with non-small-cell lung cancer, 85 of whom were in stage 1, 92 in stage 2, and 96 in stage 3. We divided the patients into three groups, based on their total serum LD values: less than 225 U/L (normal reference range), 226-500 U/L, and greater than 500 U/L. Overall values for LD were above normal at diagnosis for 69% of the patients, being moderately increased in 63 patients and highly increased in 125. Eighty percent of the patients in stage 1 had normal values for LD at diagnosis, but 88% of the patients in stage 2 and 94% of the patients in stage 3 had above-normal LD values at diagnosis. In 55% of the patients in stage 2 and 73% of the patients in stage 3, LD activity was highly increased. In the patients with normal values for total LD, the proportions of the LD isoenzymes were normal. In the patients with increased LD, the isoenzyme proportions were increased for LD-4 and LD-5, up to twice the normal values. The sensitivity of LD in detection of lung cancer was 60% for LD at the cutoff point of 250 U/L in comparison with normal controls, and 47% for LD at the cutoff point of 310 U/L in comparison with the benign lung disease group of patients (95% specificity). We conclude that total LD in serum may be a direct indicator of clinical stage and tumor burden in patients with non-small-cell lung cancer.
Midazolam in plasma from hospitalized patients as measured by gas-liquid chromatography with electron-capture detection.
Authors: Ha H R , Funk B , Maitre P O , Zbinden A M , Follath F , Thomson D A
Published: January 2020

The present assay was developed for quantifying midazolam in plasma of patients hospitalized in intensive-care units or undergoing anesthesia and receiving many other drugs as well. Plasma samples are alkalinized with NaOH and midazolam is extracted into n-hexane. The organic phase is evaporated and reconstituted in n-butyl acetate, and the midazolam is quantified by gas-liquid chromatography with electron-capture detection. The calibration graph for midazolam was linear in the ranges 5-200 and 200-800 micrograms/L. The CVs for precision and reproducibility of the assay were less than 8%. The method was very specific for midazolam; most of the drugs commonly used in anesthesia and in the intensive-care unit did not interfere with the assay. The lowest detectable concentration was 1 microgram/L. The method is adaptable for use with an automated chromatographic system.
Simultaneous determination of four monoamine metabolites and serotonin in cerebrospinal fluid by "high-performance" liquid chromatography with electrochemical detection; application for patients with Alzheimer's disease.
Authors: Koyama E , Minegishi A , Ishizaki T
Published: January 2020

We describe an optimized, sensitive assay procedure for simultaneously determining 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid, and serotonin in human lumbar cerebrospinal fluid. The assay is based on liquid chromatography with an electrochemical detection system equipped with a newly developed, highly sensitive graphite electrode. Before assay, samples are deproteinized with perchloric acid, 0.2 mol/L. The within- and between-day CVs were less than 2.5% and 6.7%, respectively, for all compounds. The lower limits of detection for 3-methoxy-4-hydroxyphenylglycol and 3,4-dihydroxyphenylacetic acid were 0.5 pg and for the other three analytes 1.5 pg per injection. Preliminary data on monoaminergic metabolites by the current assay showed that concentrations of dopaminergic and serotonergic metabolites were significantly (P less than 0.05) lower in patients with Alzheimer's disease than in the age-matched controls. In addition, the concentration of 3,4-dihydroxyphenylacetic acid correlated significantly (P less than 0.01) with that of homovanillic acid, suggesting that monitoring either of these metabolites in cerebrospinal fluid can be used as an index of central dopaminergic activity.
Total, tartrate-resistant, and tartrate-inhibited acid phosphatases in serum: biological variations and reference limits.
Authors: Schiele F , Artur Y , Floc'h A Y , Siest G
Published: January 2020

We studied several factors affecting biological variation in serum acid phosphatases in a population of 1195 apparently healthy subjects four years old or older. We assayed total acid phosphatase activities in the presence of a transphosphorylating agent and using alpha-naphthyl phosphate as substrate. The main factors modifying total and tartrate-resistant acid phosphatases activities in serum are similar to those observed for total and bone alkaline phosphatases activities: age, sex, and hormonal state (puberty or menopause). The tartrate-inhibited acid phosphatase activity is, however, independent of biological variations. Finally, we propose reference limits for total, tartrate-resistant, and tartrate-inhibited acid phosphatases in serum.
Thyroxin binding by human serum albumin after denaturation of the thyroxin-binding globulin in familial dysalbuminemic hyperthyroxinemia.
Authors: Arevalo G
Published: January 2020

Abnormal binding of thyroxin (T4) to serum albumin of subjects with familial dysalbuminemic hyperthyroxinemia (FDH) is generally demonstrated by the T4-loaded charcoal uptake test, with T4 added in excess (0.1 mmol/L) to accentuate T4 binding to albumin in FDH. I describe a binding study involving T4 tracer in which thyroxin-binding globulin is denatured in samples by treatment with mild acid at pH less than 3.0. The tracer is bound to the serum albumin and, to a greater extent, to the FDH albumin, because the binding by thyroxin-binding prealbumin is blocked by barbital buffer. The result of the [125I]T4 binding to the albumin is expressed as a T4 binding index, based on results for pooled sera from patients with normal thyroid function as a reference. The mean index in FDH was 4.08 (SD 0.92, n = 5); in hypoalbuminemia, 0.66 (SD 0.18, n = 8); in normal subjects, 1.00 (SD 0.11, n = 20). This albumin-binding index enables the rapid and unequivocal diagnosis of subjects with FDH, without the addition of unlabeled T4.
Micro-scale two-dimensional electrophoresis of alkaline phosphatase from serum.
Authors: Sanderink G J , Artur Y , Paille F , Galteau M M , Siest G
Published: January 2020

Isoenzymes of alkaline phosphatase (EC 3.1.3.1) were separated by micro-scale two-dimensional electrophoresis, with isoelectric focusing in capillary gels in the first dimension and polyacrylamide gradient-gel electrophoresis in the second. The isoenzymes detected were identified by several treatments--e.g., incubation with sialidase, papain, Triton X-100, and wheat-germ agglutinin--and by comparison with alkaline phosphatase from liver microsomes. Liver and bone isoforms in normal sera showed overlapping isoelectric points but differed in molecular mass, estimated as 172 and 185 kDa, respectively. Sera of patients with liver disease showed several additional groups of alkaline phosphatase isoforms, two of which were found to consist of multi-molecular complexes. Others probably correspond to incompletely glycated enzyme proteins. A further isoform with a mass of about 250 kDa does not seem to correspond to any known isoform of alkaline phosphatase in serum. With this technique, we demonstrated intra- and interindividual variations of the placental alkaline phosphatase isoenzyme in pregnancy sera.
Reversible loss of lactate dehydrogenase isoenzymes and lactate dehydrogenase activity in patient's serum.
Authors: Kraaijenhagen R J , Backer E T
Published: January 2020

An abnormal lactate dehydrogenase (LD; EC 1.1.1.27) electrophoretogram (only one band, at the application site) and a low LD activity (7 U/L) was seen for a patient's serum during storage at 22 and 4 degrees C. Both reverted to normal when the serum was incubated at 37 degrees C.
Clinical diagnosis of mood disorders.
Authors: Rush A J
Published: January 2020

The history of syndrome-based diagnosis is reviewed. Recent criteria for the mood disorders according to the American Psychiatric Association are presented. Issues in the differential diagnosis of the mood disorders are discussed. Finally, commonly encountered pitfalls in clinical descriptive diagnosis and their potential remedies are summarized.
Medicolegal alcohol determination: Widmark revisited.
Authors: Simpson G
Published: January 2020

Several concepts and principles advanced by Widmark over 50 years ago are briefly compared with results of recently published experimental work. His conclusions--that breath alcohol analysis can lead to overestimates of actual blood alcohol concentration, and that +/- 2 standard deviations about the average should be used to estimate certain pharmacokinetic parameters for medicolegal alcohol determinations--are supported by these more-recent experimental results.
Valproic acid and the liver.
Authors: Cotariu D , Zaidman J L
Published: January 2020

Valproic acid (VPA) is widely used as an anticonvulsant, but therapy with the drug has been associated with hepatotoxicity, either reversible hepatic dysfunction or irreversible hepatic failure. Both clinical and experimental studies have revealed several VPA-related biochemical abnormalities in the liver: inhibition of the beta-oxidation and synthesis of fatty acids and inhibition of gluconeogenesis, urea synthesis, oxidative phosphorylation, and the glycine cleavage system. Other abnormalities noted include alteration in the protein conformation of the internal mitochondrial membrane, hyperammonemia, and increased bile flow. The mechanisms of such hepatotoxicity, whether mediated by VPA or by its metabolites, are still little understood. Susceptibility to VPA hepatotoxicity may be enhanced by such conditions as starvation, inborn errors of metabolism, additional neurological disease, and concomitant administration of enzyme-inducing drugs.
Creatine kinase MB in cases of skeletal muscle trauma.
Authors: Schwartz J G , Prihoda T J , Stuckey J H , Gage C L , Darnell M L
Published: January 2020

Fifty-eight patients admitted through our emergency room with severe skeletal muscle injury but no obvious cardiac contusions were evaluated for creatine kinase isoenzyme MB (CK-MB). When such patients show an above-normal value for total CK, it is a question of whether or not myocardial injury has been sustained along with skeletal muscle injury when (a) there are no obvious chest contusions or (b) the patient is unconscious and unable to complain of chest pain. Whenever there is doubt concerning the cardiac status of a patient, lactate dehydrogenase (LD) isoenzymes, serial electrocardiograms, and CK isoenzymes are ordered. Our study revealed that serum of 8.6% of the trauma victims had CK-MB values exceeding 5.0 EU/L (reflecting abnormal CK-MB concentrations) as part of their increased total CK. All patients had normal electrocardiographic patterns along with negative results for LD isoenzymes; none had sustained any demonstrable myocardial injury. The CK-MB value must be interpreted together with the total CK value for appropriate diagnosis in patients with skeletal muscle trauma.
Interference of fetal hemoglobin with the spectrophotometric measurement of carboxyhemoglobin.
Authors: Vreman H J , Ronquillo R B , Ariagno R L , Schwartz H C , Stevenson D K
Published: January 2020

We measured the concentration of carboxyhemoglobin (HbCO) in blood samples from 32 neonates by spectrophotometry (IL282 CO-Oximeter) and gas chromatography, finding a strong positive correlation (r = 0.89) between the concentration of fetal hemoglobin (Hb F) and HbCO as measured by spectrophotometry, but not by gas chromatography. Thus, Hb F interferes with the determination of HbCO by spectrophotometric techniques by falsely increasing apparent HbCO in direct proportion to Hb F. We conclude that, when Hb F is known or suspected to be present, blood HbCO cannot be reliably determined by methods based on spectrophotometry.
Immunoreactive pancreatic phospholipase A2 and catalytically active phospholipases A2 in serum from patients with acute pancreatitis.
Authors: Eskola J U , Nevalainen T J , Kortesuo P
Published: January 2020

Measuring the content of immunoreactive pancreatic phospholipase A2 (PLA2; EC 3.1.1.4) and the catalytic activity of PLA2 in serum samples from five patients with acute pancreatitis, we found no correlation between these two measurements overall. To test the specificity of the method for catalytic PLA2, we measured PLA2 activity in serum samples before and after immunoadsorption with an antiserum to human pancreatic PLA2. The results suggest the presence of at least two immunologically distinct PLA2 enzyme proteins in sera from these patients. One of the enzymes is pancreatic in origin and may exist in active, inactive, or inhibited form. The activity profile of the second PLA2 enzyme in serum during acute pancreatitis differs from that for other common pancreatic enzymes. In the present experiment, the catalytic activity was not removed by treatment with the anti-human pancreatic PLA2 antiserum. The source of this second PLA2 activity is unknown. Some samples contained increased activities of both PLA2 forms.
Opioid peptide profile in human pituitary.
Authors: Desiderio D M , Fridland G H , Francisco J T , Sacks H , Robertson J T , Cezayirli R C , Killmar J , Lahren C
Published: January 2020

The comprehensive metabolic profile of endogenous opioid peptides is established here for human pituitary for the first time. Sixteen human pituitaries, obtained postmortem, were analyzed individually by gradient reversed-phase high-performance liquid chromatography together with a radio-receptor assay with [3H]etorphine as ligand. This combination was used to detect opioid receptor activity. The 16 assay profiles were sufficiently consistent for a composite of them to serve as a comparative basis for other studies on the pathophysiology of the human pituitary. To demonstrate one selected comparison, we present data on a distinctively different profile of opioid receptor activity in the pituitary of one patient who died from a drug overdose.
Revised calibration of the Reflotron cholesterol assay evaluated.
Authors: Boerma G J , van Gorp I , Liem T L , Leijnse B , Bellm J , Carstensen C A
Published: January 2020

We evaluated the Boehringer Mannheim (B.M.) Reflotron Total Cholesterol "dry-chemistry" method after its recalibration in 1987. Reports in the literature up to 1986-1987 of a negative bias (up to -10%) in the method prompted a revision of the factory-set calibration of the Reflotron. For this, B.M. prepared a new set of calibrators with 12 different concentrations of cholesterol. We checked in two ways whether accuracy had been achieved: (a) The values assigned to the calibrators by B.M. were checked with the manual Abell-Kendall Reference Method (MAK) performed in an official Reference Center. These were shown to be correct. (b) Concurrently, a direct comparison was made by analyzing 200 fresh samples of human serum. Reflotron cholesterol values obtained for these samples proved to be accurate, meeting the current World Health Organization/Centers for Disease Control criterion of maximum bias less than or equal to 5%. Orthogonal regression analysis yielded the following correlation: Reflotron = 0.985 MAK + 0.238 mmol/L (y = ax + b). Reflotron mean = 6.26 mmol/L; MAK mean = 6.09 mmol/L. SDa = 0.015 mmol/L; SDb = 0.120 mmol/L, and r = 0.989.
A review on the methodology for assessing diagnostic tests.
Authors: Linnet K
Published: January 2020

Evaluation of diagnostic tests by the following principles are reviewed: error rates, scores based on posterior probabilities, and the excess loss considered in a decision theoretic context. Error rates or the complementary non-error rates, specificity and sensitivity, are simple measures which provide a rough indication of the discriminative value. In clinical practice, where a test serves as a decision support together with other information, conversion of test results to posterior probabilities is recommended. An aggregate score of these probabilities expresses the value of the test. Finally, in simple, well-defined cases--for example, screening situations, where the prevalence of disease and the relative consequences of false-positive and -negative classifications can be estimated--a Bayesian decision analysis is appropriate. The optimal discrimination limit is selected, and the total loss is minimized. The likelihood ratio LR(x) plays a central role in probability calculations and in the decision analysis. An example illustrates application of the procedures.
Particle counting immunoassay of S100 protein in serum. Possible relevance in tumors and ischemic disorders of the central nervous system.
Authors: Fagnart O C , Sindic C J , Laterre C
Published: January 2020

S100 protein (S100) was assayed by particle counting immunoassay in serum samples from 50 healthy individuals, 325 patients with various neurological disorders, and 20 patients with malignant melanoma. The detection limit for this protein was 0.3 microgram/L. We detected none in healthy individuals or in 50 patients with multiple sclerosis, 23 with dementia, or 20 with meningitis. S100 was detectable in serum of only a few patients with meningoradiculitis (2/20), peripheral neuropathy (2/30), encephalitis (1/14), Guillain-Barré syndrome (1/25), or AIDS (2/20). In contrast, we observed high concentrations in 29 of 75 patients with tumors of the central nervous system, especially in meningioma (6/9), glioblastoma (9/23), and neurinoma (5/5). Values for S100 were mainly abnormally high (greater than 0.3 microgram/L) in serum from patients with cerebrovascular disorders (43/48) or with metastases of melanoma (9/11).