Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Methods”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1987

Precision of glucose measurements in control sera by isotope dilution/mass spectrometry: proposed definitive method compared with a reference method.

This improved isotope-dilution gas chromatographic/mass spectrometric (GC/MS) method, in which [13C]glucose is the internal standard, meets the requirements of a Definitive Method. In a first study with five reconstituted lyophilized sera, a nested analysis of variance of GC/MS values indicated considerable among-vial variation. The CV for 32 measurements per serum ranged from 0.5 to 0.9%. However, concentration and uncertainty values (mmol/L per gram of serum) assigned to one serum by the NBS Definitive Method (7.56 +/- 0.28) were practically identical to those obtained with the proposed method (7.57 +/- 0.20). In the second study, we used twice more [13C]glucose diluent to assay four serum pools and two lyophilized sera. The CV ranged from 0.26 to 0.5% for the serum pools and from 0.28 to 0.59% for the lyophilized sera. In comparison, results by the hexokinase/glucose-6-phosphate dehydrogenase reference method agreed within acceptable limits with those by the Definitive Method but tended to be slightly higher (up to 3%) for lyophilized serum samples or slightly lower (up to 2.5%) for serum pools.

Blood Chemical Analysis↗
PubMedDate not supplied

Comparison of modified automatic Dumas method and the traditional Kjeldahl method for nitrogen determination in infant food.

This study compares 2 methods for determining nitrogen and protein in various types of infant food: the Kjeldahl method, developed in 1883, which is time consuming and labor intensive, and a newer, automatic method, based on the Dumas method. In each category of infant food considered, the results obtained from both methods are shown to be comparable; however, the modified Dumas method is quicker, easier, and does not pollute the laboratory environment.

Autoanalysis↗
PubMed1987

The Ames Clinitek 200/Multistix 9 urinalysis method compared with manual and microscopic methods.

We assayed 315 urine specimens by the Ames Clinitek 200/Multistix 9 semi-automated method and by corresponding standard methods (listed in parentheses) for the following analytes: protein (sulfosalicylic acid precipitation), glucose (Lilly Tes-Tape), ketones (Boehringer Mannheim Chemstrip K), leukocyte esterase (microscopic examination for leukocytes), blood (microscopic examination for erythrocytes), nitrite (microscopic examination for bacteria, Gram stain, or culture), and pH (pH meter). The Clinitek and standard methods agreed well at all concentrations for protein, ketones, and glucose. The Clinitek leukocyte esterase, nitrite, and blood methods were less sensitive than microscopic methods for detection of pyuria, bacteriuria, and hematuria, respectively. The Clinitek pH method produced falsely low pH values for urines with true pH less than 6.5, and falsely high values for urines with true pH greater than 6.5.

Autoanalysis↗
PubMed1985

[A quantitative study of brain atrophy on computed tomography--multivariate analysis for comparison between the linear measurement method and the pixel count method].

We previously reported the newly developed quantitative measurement of the cerebral atrophy. The data indicated that the volume of the cerebrospinal fluid not always gradually increases during the life course but remains relatively constant until age 50 and thereafter increases with a wide variation. Though the technique, which is called the pixel count method, is highly quantitative, it is quite troublesome as it needs the computer to count out each pixels. On the other hand, the linear measurement method is easier than the pixel count method, but is far less quantitative. We examined seventy four subjects using both the linear measurement method and the pixel count method, and compared them by means of the multivariant analysis. Three different linear measurement methods were selected by the stepwise multiple regression analysis, those are B (distance between the caudate nuclei), E (greatest distance between the lateral ventricles at the level of the cella media) and G (number of visible sulci whose width are more than 3.1 mm at the level of 3 cm above the corpus callosum). B and E were calibrated by the maximum internal width of the skull (H). The highest correlation was achieved with a formula employing these parameters as follows; y = 42.66 X B/H + 12.52 X E/H + 0.232 X G - 2.92 (y means the estimated value of the CCR (CSF-cranial ratio), which is obtained by dividing the CSF volume by the cranial cavity). Multiple correlation coefficient was 0.76, and was statistically significant (p less than 0.001). The authors emphasized that using this formula we can easily predict CCR as the index of the brain atrophy without any computer.

Adult↗
PubMedDate not supplied

Performance characteristics of methods of analysis used for regulatory purposes. I. Drug dosage forms. E. miscellaneous methods.

Precision parameters of miscellaneous methods for the analysis of drug dosage forms approved by AOAC since 1972, and not previously reviewed in this series, were recalculated on a consistent statistical basis by using the computer program FDACHEMIST. Seventeen published collaborative studies were reviewed; the studies encompassed 19 analytes in 80 different materials (dosage forms), 102 collaborative assays, approximately 10 laboratories per study, and principally direct spectrophotometric, polarographic, and spectroscopic methods, for a total of 1451 determinations. The average repeatability relative standard deviation (within-laboratories, RSDo) for the instrumental methods was 1.5%; the reproducibility relative standard deviation (among-laboratories, including within-, RSDx) was 2.6%; the ratio RSDo/RSDx of the averages was 0.57, with an average outlier rate of 2.7% of the reported determinations. The line of best fit of RSDx for the instrumental methods plotted against the negative logarithm of the concentration increases slightly with decreasing concentration, extending from an RSDx of approximately 2.0% at 100% concentration to an RSDx of 3.4% at 0.001% (10 ppm) concentration; this represents an RSDx change of approximately 0.3% (absolute) for each 10-fold decrease in concentration, independent of analyte, matrix, and method. A method for determining precipitated allergenic protein by the micro-Kjeldahl technique appeared to be outside this general relation, showing an RSDx of about 13% at a concentration of 0.015% (150 ppm) nitrogen.

Allergens↗
PubMed1984

Mobility of the pubic symphysis. In vivo measurements with an electromechanic method and a roentgen stereophotogrammetric method.

Mobility of the pubic symphysis can be measured in vivo by two new methods. One is electromechanic (EM), with steel pins inserted into the bone. The other is roentgen stereophotogrammetric analysis (RSA), with tantalum bone markers implanted into the hip bones. With the first method, movements are directly registered with resistive transducers mounted on the pins. With the second method, movements are deduced with kinematic analysis from roentgen stereophotogrammetric measurements of the positions of the bone markers. Both methods have high precision, about 0.1 mm for translations and 0.1 degrees for rotations. The methods were used in two young volunteers, a man and a woman. In provocative tests with identical loading (alternating, active straight-leg raising in the supine position and standing on alternating left or right leg) there was a good correlation between the two methods. The measured values, i.e., translations of up to 2 mm and rotations of up to 3 degrees, form a basis for more comprehensive studies of normal and pathologic mobility of the pubic symphysis.

Adult↗
PubMed1982

Lipoprotein quantification: an electrophoretic method compared with the Lipid Research Clinics method.

We compared a turbidimetric electrophoretic method (Lipidophor) for lipoprotein quantification with the standardized Lipid Research Clinics (LRC) method. In the Lipidophor procedure, major lipoproteins are separated by electrophoresis on agarose gels, precipitated on the gels with phosphotungstate-Mg2+ reagent, and the resulting turbidity is measured densitometrically. Measurements of relative turbidity were converted into lipoprotein cholesterol values by the use of numeric constants provided by the manufacturer. Among-day CVs (n = 46) for the Lipidophor method were 6.0%, 3.6%, and 9.9% for cholesterol in the alpha-, beta-, and pre-beta lipoproteins, respectively. The Lipidophor alpha-cholesterol was significantly lower (n = 171 specimens) than the LRC high-density lipoprotein (HDL) cholesterol (514 vs 586 mg/L), and beta-cholesterol was significantly higher than the corresponding LRC low-density lipoprotein (LDL) cholesterol values (1505 vs 1409 mg/L). The linear relation between the two methods for lipoprotein cholesterol quantification is as follows: Lipidophor alpha = 0.77 LRC HDL + 63 mg/L with correlation coefficient (r) of 0.87; Lipidophor beta = 0.95 LRC LDL + 166 mg/L (r = 0.96); Lipidophor pre-beta = 0.57 LRC very-low-density lipoprotein + 39 mg/L (r = 0.82). We derived a revised algorithm for estimating lipoprotein cholesterol from turbidity measurements. Lipoprotein cholesterol values by the Lipidophor method agree well with those obtained by the LRC method when these constants are used.

Adult↗
PubMed1981

Comparison of automated method and improved AOAC Kjeldahl method for determination of protein in meat and meat products.

The Kjel-Foss automated method for protein determination meat and meat products was compared with the improved AOAC Kjeldahl method. Meat samples were separated into 3 categories based on fat content and analyzed in duplicate by both methods. No significant difference was found in a paired comparison of the 2 methods in each of the 3 meat categories, using Student's t-test at the 99% confidence level. A number of additional meat samples analyzed 6-9 times by the automated method showed an overall average range of 0.55% protein and average standard deviation of 0.20. The Kjel-Foss automated method was applicable for total protein determination in a wide variety of meat and meat products.

Animals↗
PubMedDate not supplied

Comparative and multilaboratory studies of two immunodiffusion method enrichment protocols and the AOAC/Bacteriological Analytical Manual culture method for detection of Salmonella in all foods.

The single enrichment immunodiffusion (1-step), the preenrichment and selective enrichment immunodiffusion (2-step), and the AOAC/Bacteriological Analytical Manual culture methods for Salmonella were evaluated for equivalence in 2 separate studies, a comparative evaluation and a multilaboratory dilution study. In the comparative study, all 3 methods were performed on 10 food types. For 550 samples, analyses resulted in 99.3 and 99.6% agreement between the culture method and the 1-step and 2-step methods, respectively. False negative rates were 0.9 and 0.3% for 1-step and culture, and 0.0% and 0.6% for the 2-step and culture, respectively. Subsequently, 6 food types were included in a multilaboratory dilution-to-extinction study. A sequential dilution series of Salmonella in foods was analyzed by the 3 methods to determine their lower limits of detection for Salmonella. A total of 1185 samples analyzed resulted in 98.9% agreement between 1-step and culture, and 99.7% agreement between 2-step and culture. False negative rates were 1.8 and 0.1% for 1-step and culture, and 0.4 and 0.1% for 2-step and culture, respectively. During these evaluations, 1735 samples and controls representing 10 different naturally contaminated and inoculated foods were tested. The data indicate statistical equivalence of all 3 methods when analyzing all food types.

Bacteriological Techniques↗
PubMed1993

Egg viability in urinary schistosomiasis. I. New methods compared with available methods.

A new method of quantifying viability and hatchability of Schistosoma haematobium eggs in urine has been developed. It consists of filtering urine samples through Nytrel filters followed by mercurochrome staining to assist in the detection of viable (motile) miracidia in egg shells, and iodine staining to show hatched miracidia. The new method is compared with two existing techniques for viability/hatchability determination, centrifugation hatching and Nuclepore filtration trypan blue staining. Seventy-three egg positive urine samples are compared; the overall proportions of viable eggs are very close for centrifugation hatching and the new method, but 33% of eggs are lost in centrifugation and 19% of eggs are unclassifiable by Nuclepore filtration trypan blue staining. The main advantages and disadvantages of the new and existing methods are described and discussed; the cheapness, simplicity and ease of performance of the new method make it suitable for large-scale field use. Suggestions for improvements and standardization of the new method are made.

Animals↗
PubMed1982

Polyamine cytochemistry. Use of a novel o-phtalaldehyde method for visualizing spermidine and spermine. Comparisons to the formaldehyde-fluorescamine method.

o-Phtalaldehyde (OPT) reacts with a number of biologically important molecules, including the polyamines, spermidine and spermine. By systematically varying reaction conditions with respect to temperature, pH, concentration and length of exposure to the reagent, using both model systems and tissues, we have succeeded in constructing a cytochemical OPT-method specific for spermidine and spermine. The method detects cell types known to contain these polyamines, including growing and neoplastic cells. The staining pattern obtained with the OPT method is identical to that obtained with the formaldehyde-fluorescamine (FF) technique recently shown to be specific for spermidine and spermine. In contrast to the FF technique, the OPT method can be used for staining suspensions of isolated cells and may hence be employed in studies using fluorescence-activated cell sorting (FACS). Preliminary such studies show a pronounced decrease in cellular OPT-induced fluorescence, paralleled by a decrease in content of polyamines, after treatment with the polyamine biosynthesis inhibitor alpha-difluoromethylornithine (alpha DFMO). In contrast, cells simultaneously treated with alpha DFMO + spermidine show pronounced increases in their spermidine content and parallel increases in their OPT-induced fluorescence. Availability of methods selectively demonstrating polyamines at the cellular and subcellular level is expected to aid our understanding of polyamine functions in normal growth and cancer.

Aldehydes↗
PubMed1993

Simplified methods for the evaluation of the parameters of the time course of plasma concentration in the one-compartment body model with first-order invasion and first-order drug elimination including methods for ascertaining when such rate constants are equal.

The many limitations in determining the pharmacokinetic parameters of first-order invasion of, and elimination from, the one-compartment body model by the method of residuals or by "feathering" C-t data can be minimized by applying the simplified methods outlined herein. Comparisons of the apparent volumes of distribution, V, calculated on the premises that the Bateman Function represents ka > ke or its converse, ke > ka, i.e., flip-flop, can permit a proper choice of the correct version. Estimation of ke can be obtained by regression of (A0/V)/C(oncentration) on AUCt/C where A0/V is estimable from knowledge of Cmax and tmax since A0/V = Cmax eketmax. The ratio of the magnitude of the rate constant of invasion to that of elimination, m = ka/ke, is related to ketmax by the expression ketmax = ln m/(m - 1) for all possible values of m. A table for the determination of m from values of ketmax is given. When bioavailability, gamma = Ao/Dose, is known or complete, ke and V can be determined from the respective ordinate and abscissa of the intersection of A0/Cmax eketmax and Cl(clearance)/ke, both plotted against arbitrary ke values. The two functions may not intersect at low values of m due to errored C-t values but the ke value when the two curves are closest (kmin) may approximate ke. The intersections of Cmax eketmax and keAUCT (AUCtrap) plotted against variable ke values (Method A) provide estimates of ke from their abscissa values and A/V from their ordinate values when gamma is unknown. Method B appears to give more reliable estimates of ke at the kmin of the difference eketmax/ke - AUCT/Cmax, plotted against ke. Since kmin of this plot is l/tmax when m = 1, the identity of the m as unity underlying the C-t data is indicated when either kmintmax is approximately unity or kmin is practically synonymous with l/tmax. This was clearly shown when 12 constructed m = 1, C-t cases with 10% random error were evaluated by Method B. Better estimates were effected by all procedures when the raw C-t data were smoothed.

Biological Availability↗
PubMed1980

The determination of ammonium in Kjeldahl digests using the gas-sensing ammonia electrode. Comparison of the direct method with the known-addition method.

The efficacy of the ammonia electrode for analysis of the nitrogen content of a large series of Kjeldahl digests was investigated. By using this electrode, two methods for the measurement of ammonium concentrations were compared, the direct method and the known-addition method. When the direct method was used, a marked shift in the electrode potential occurred within a few hours, causing errors of 9-17% in the results. When the ammonium concentrations were calculated from the difference in electrode potential before and after addition of a known amount of an ammonium standard solution (known-addition method), it was possible to carry out reproducible measurements and the shift in the electrode potential did not influence the results. In two series of identical samples the coefficient of variation was respectively 1.45% and 0.80%.

Ammonia↗
PubMed1989

The vaginal contraceptive diaphragm and the condom--a reevaluation and comparison of two barrier methods with the rhythm method.

The use-effectiveness and continuation rates of two barrier methods of contraception, the diaphragm and condom, were studied during a two-year follow-up in a group of 85 and 98 women, respectively. All were highly motivated. Results were compared to a group of 64 women using the periodic abstinence or rhythm method, i.e. not using any contraceptive. The patients selected the method of contraception they preferred and were instructed in their proper use. Results showed good continuation rates in the groups using a diaphragm and the condom for 2 years, for a total follow-up of 5570 cycles. Pregnancy rate after 24 months of use, as calculated by Pearl's formula, was 2.48 for the diaphragm, 3.21 for the condom, and 5.19 in the rhythm group. No serious side effects or complications occurred in either group. The study demonstrated a fair acceptability and use-effectiveness for barrier contraceptive. We suggest that these harmless and complication-free methods may still be reasonable alternatives for the "modern" methods, the pill and the IUD.

Adolescent↗
PubMed1975

Catecholamines in urine; an evaluation of alumina-trihydroxyindole methods and a description of an improved method.

A critical assessment of the accuracy and practicability of five alumina-trihydroxyindole methods for the estimation of urinary catecholamines, including our proposed method, was undertaken. The recovery of noradrenaline added to urine obtained by these methods was quantitated against different types of standards, and varied from 22.9 per cent to 104.8 per cent. The major analytical problems (fluorescence suppression and loss of catecholamines during column chromatography) were evaluated and related to the recovery of the respective procedures. The improved method we developed is simple, rapid and reliable. The low fluorescence suppression and column losses of noradrenaline of this method, averaging 2.9 per cent and 5.3 per cent, respectively, resulted in a mean recovery of 92.0 per cent against an external standard. Both the chromatography step and fluorescence development are simple and short, and a batch of ten cases can be completed within 3 hours.

Aluminum↗
PubMed1988

Comparison between the photoelectric method and H2 clearance method for measuring cerebrocortical blood flow in cats.

The photoelectric method using carbon black as a nondiffusible tracer of blood was compared with the hydrogen clearance (H2) method in nine anesthetized cats. A photoelectric apparatus and H2 electrode were applied to a small region of the cerebral cortex (left ectosylvian gyrus) for simultaneous measurement of the regional CBF. The values of CBF(H2) and CBF(photoelectric) were 50.7 +/- 19.2 and 52.1 +/- 14.5 ml.100 g-1.min-1, respectively. CBF(H2) and CBF(photoelectric) were found to correlate well (r = 0.588, p less than 0.01) when changes in CBF were induced by CO2 inhalation, exsanguination, hyperventilation, and occlusion of the middle cerebral artery. The correlation between CBF(H2) and CBF(photoelectric) was much better in the case of intraindividual comparisons (r = 0.957, p less than 0.01). In addition to its merits in common with the H2 clearance method, such as handiness, low cost, and strict regionality, the photoelectric method displayed the following advantages: time-to-time measurements of CBF (less than 20 s), immediate display of the microcirculatory flow pattern, and simultaneous monitoring of cerebral blood volume. However, measurements from deep structures of the brain are better performed by the H2 method despite the disadvantage of the use of a potentially explosive gas.

Animals↗
PubMed1985

A comparison of reference method values for sodium, potassium and chloride with method-dependent assigned values.

The concentrations of sodium, potassium, and chloride in various control sera were determined by reference methods. The reference method values were compared with the corresponding method-dependent assigned values. Sodium: Measurements by flame photometry and ion selective electrodes differed on the whole by less than 1% from the reference method value; determinations by photometry differed, however, by -4.7%. Potassium: The mean bias was -1.2% with flame photometry and -0.4% with ion selective electrodes, whereas nephelometric procedures differed by -1.9 or -4.8%. Chloride: Satisfactory agreement was obtained with values given for ion selective electrodes (-0.3%), for some coulometric procedures (-0.7 and 0.4%), and photometric determinations using mercury rhodanide (-0.5 and +0.7%). Values for mercurimetric titration and for photometric determinations using mercury 2,4,6-tri-(2-pyridyl)-s-triazine differed by + 2.5 and + 1.8%. Proposals concerning the allowable deviation from reference method values are discussed.

Chlorides↗
PubMed1988

[The determination of oxalate in urine by enzymatic method using oxalate oxidase: comparison between enzymatic and gas-chromatographic methods].

Urinary oxalate is one of the most important constituents of urolithiasis, but the determination of oxalate in urine has not been performed as a routine laboratory examination. We tried to measure oxalate in urine by the enzymatic method with oxalate oxidase. The linearity of the standard curve and reproducibility of this method were confirmed. (Linearity: r = 0.996, S.D./mean: 0.5-3.6%, recovery rate: 99.5 +/- 3.3 (mean +/- S.D.)%) The correlation between this method and gas-chromatographic method was 0.926. The enzymatic method with oxalate oxidase can be utilized for determining the urinary oxalate as a routine laboratory examination.

Chromatography, Gas↗