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.

SourceResearch connectionFrom yearThrough year

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

At least 181 records · Page 10Linked to original sources

PubMed1985

Methods of assigning accurate values to reference serum. Part 2. The use of definitive methods, reference laboratories, transferred values and consensus values.

Eight analytes (Ca, Cl, cholesterol, glucose, Mg, K, Na and urate) have been determined in one horse serum masterlot by up to six different procedures: (i) by so-called definitive methods; (ii) by a group of reference laboratories using a variety of analytical methods; (iii) using the results of two independent external quality assessment schemes; (iv) by transferring values from a human serum standard reference material analysed by definitive methods; (v) by similar transfer of values from several batches of horse reference serum previously analysed by definitive methods; and (vi) as in (v) but using a group of reference laboratories. The results have confirmed the validity and usefulness of the transfer process in value assignment and in identifying outliers due to inaccurate methods. Definitive methods are shown to be subject to error, and although they appear to be the most accurate single techniques currently available, they are not definitive in the sense of being without bias and having no known source of inaccuracy.

Animals↗

PubMed1989

Comparison of the reflectance method (Reflotron reflectance photometer) with the absorbance method (automatic analysers) for the determination of cholesterol.

The European Atherosclerosis Society (1) and the Expert Panel of the US National Cholesterol Education Program (2) have issued detailed guide values for recognition and management of hyperlipidaemia in adults. In these guidelines, the diagnosis of dyslipidaemia based on the measurements of total cholesterol, triacylglycerols, HDL and LDL cholesterol plays an important role. A prerequisite for the desired success of interventive measures is the reliability of the analytical data. The aim of this study was to investigate the precision and accuracy of Reflotron Cholesterol, a method based on the dry chemistry principle. Accuracy was assessed by establishing the correlation with the standardized automated methods used in routine lipid diagnosis. In addition, it was also examined whether the Reflotron Cholesterol results in plasma and blood are comparable. The Reflotron cholesterol (sample: blood) showed a good correlation with the CHOD/PAP method on a Hitachi 737 instrument (sample: plasma). The median value of the differences of the test results was -0.4%. Similarly, the method comparison of Reflotron Cholesterol (sample: blood) versus CHOD/PAP method on a SMAC instrument (sample: plasma) showed that Reflotron produces slightly (1.8%) higher results. The Reflotron Cholesterol values obtained from blood samples were slightly lower than those from plasma samples (median value of the differences: -2.2%). The results suggest that for routine purposes Reflotron Cholesterol provides results which are in good agreement with those obtained by standardized wet chemistry methods.

Autoanalysis↗

PubMed1995

Performance of a direct, immunoseparation based LDL-cholesterol method compared to Friedewald calculation and a polyvinyl sulphate precipitation method.

The analytical performance of a direct, immunoseparation based LDL-cholesterol method (Genzyme Corporation) was evaluated on an ELAN analyser (Merck), and compared with the performance of routinely used methods (LDL-cholesterol estimated by the Friedewald equation, and LDL-cholesterol obtained after polyvinyl sulphate precipitation). Within-day coefficients of variation (CVs) were 0.79 to 2.51% for immunoseparation based LDL-cholesterol; the between-day CVs varied between 2.62 and 3.89%, i.e. within the recommended National Cholesterol Education Program (NCEP) goal of < 4%. A method comparison study, according to the National Committee for Clinical Laboratory Standards (NCCLS) EP9-P guidelines, was performed using fasting normo- and hypertriacylglycerolaemic as well as cholestatic sera. In fresh normotriacylglycerolaemic sera immunoseparation based LDL-cholesterol (y) and Friedewald LDL-cholesterol (x) values were identical as slope and intercept of the Passing & Bablok regression equation were not significantly different from one and zero, respectively (y = 1.006 x -0.107; N = 45). In contrast, immunoseparation based LDL-cholesterol (y) differed significantly from polyvinyl sulphate LDL-cholesterol (x) results (y = 0.922 x + 0.234; N = 103). Freezing normotriacylglycerolaemic sera (three weeks, -20 degrees C) resulted in a negative bias of -5.8% for the immunoseparation based LDL-cholesterol method, and in a positive bias of +5.3% for the polyvinyl sulphate method, compared to fresh specimens. Immunoseparated LDL-cholesterol was completely recovered up to at least 37.84 mmol/l serum triacylglycerols. We conclude that the immunoseparation based LDL-cholesterol method is a practical, not technically demanding technique well applicable within routine clinical laboratories.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1976

Measurement of intrahepatic shunted blood flow by ethanol-1-14C method as compared with D-galactose-1-14C method.

Ethanol-1-14C method for the measurement of intrahepatic shunted blood flow was compared with the method of continuous infusion of D-galactose-1-14C. In controls, in chronic hepatitis, and in hepatic cirrhosis, per cent intrahepatic shunt measured by the ethanol-1-14C- method was about a half or one-third of that measured by the D-galactose-1-14C method. Study of radioactivity-dye concentration ratio of the blood sampled from the inferior vena cava showed that per cent intrahepatic shunt was underestimated by the ethanol-1-14C method because of permeability of ethanol-1-14C through the capillaries. In patients with hepatic carcinoma, in whom the carcinomatous tissue was supplied mainly by the hepatic artery, there was no significant difference in per cent intrahepatic shunt between both methods.

Ethanol↗

PubMed1983

Modulation of optical density by sulfhydryl reagents in microbiuret method: a modified method for protein determination in the presence of sulfhydryl reagents.

2-Mercaptoethanol increases the optical density of assay solutions at wavelengths between 280 to 400 nm, and therefore interferes with the measurement of protein concentration by the microbiuret method. Protein concentration can be determined in the presence of 2-mercaptoethanol up to 6 mM by modification of the method as follows: after the precipitation of protein by trichloroacetic acid in the presence of deoxycholate, the precipitate is resolubilized with NaOH solution. Dithiothreitol interfered with the protein determinations could by made in the presence of 4 mM of dithiothreitol with the modified microbiuret method. This modified method is time-saving and more reliable than other methods for protein determination, such as Lowry's method, in the presence of sulfhydryl reagents.

Proteins↗

PubMed1995

Detecting erythromycin resistance in Streptococcus pyogenes: reliability of the disk diffusion method and the breakpoint susceptibility testing method. Finnish Study Group for Antimicrobial Resistance (FIRE).

Erythromycin susceptibility of clinical Streptococcus pyogenes isolates was determined at 19 Finnish clinical microbiology laboratories by their routine disk diffusion method and by a screening method adapted from the breakpoint susceptibility testing method. Results obtained at 12 laboratories using 4 major variants of the disk method were further evaluated. From these laboratories, 286 consecutive resistant and 349 consecutive susceptible isolates were sent to the Antimicrobial Research Laboratory, Turku where the MIC of erythromycin was determined. 96% and 97% of the disk results were correct, as compared with MIC results, when general and laboratory-specific breakpoints, respectively, were used. The results of the screening method were comparable to those of the disk method.

Drug Resistance, Microbial↗

PubMed1992

The AMeX method: a multipurpose tissue-processing and paraffin-embedding method. Extraction of protein and application to immunoblotting.

The authors have previously reported a new fixation and paraffin-embedding method (the AMeX method), which preserves many antigens as well as high molecular-weight DNA and RNA that are normally destroyed by the routine formalin fixation and paraffin-embedding process. In the present study, the authors analyzed the preservation of protein suitable for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting in tissue fixed by the AMeX method. The method used for extraction of protein from AMeX-processed tissue sections after deparaffinization was the same as that for extraction from fresh tissues. The total amount of protein extracted from 50-mg (wet weight) AMeX-processed mouse liver tissue was the same as that from fresh tissue. The electrophoretic mobility and staining intensity of protein on SDS-polyacrylamide gel, and the immunoblotting pattern and staining intensity with several antibodies, were identical for both AMeX-processed and fresh tissue. Degradation of protein was minimal for storage periods of 2 years in paraffin block. The authors also showed that pellets of cultured cells can be processed by this method for immunologic analysis. This new fixation and paraffin-embedding method is a useful tool for obtaining information on correlations between morphologic features and immunochemical and molecular biological data.

Animals↗

PubMed1992

[Counting efficacies of the CFU-enumerating method and microscopic counting method for mycobacteria located in cultured macrophages].

I compared counting efficacies of CFU-enumerating method for the number of mycobacteria (Mycobacterium intracellulare and M. fortuitum) locating in cultured macrophages with that of microscopic counting method. Zymosan A-induced macrophages from ddY mice were infected with either M. intracellulare or M. fortuitum by incubation in 10% FBS-RPMI 1640 medium containing the organisms for 1 hr, thereafter thoroughly washed to remove extracellular bacilli, and cultured for 3 to 5 days. At intervals, macrophages were thoroughly rinsed and subjected to either CFU-enumeration or microscopic counting, as follows. In the former method, macrophages were lysed with 0.2% Tween 80-distilled water by sonication using Handy Sonic and CFUs were counted on 7H11 agar plates. In the latter method, the number of acid-fast bacilli was counted by microscopy for macrophages after Ziehl-Toda's staining. The number of bacteria by the CFU-enumerating method was much greater than that by the microscopic counting method.

Cell Count↗

PubMed1991

[Comparison of the identification of Enterobacteriaceae by conventional method and computer analytical method].

The purpose of this study was to compare the effectiveness of identifying Enterobacteriaceae by either the conventional method or computer analytical method. The clinical isolates of 1124 species were examined by these two methods, and 1091 species had the same results. Thus the correspondence rate was 97.1%. The inconsistence of the conventional method was usually due to personal factors and the amount of the biochemical reagents. Using the computer analytical method, error due to personal reading could be eliminated. Computer analytical method is also more effective, economical, time-saving and higher in reproductability.

Computers↗

PubMed1991

[Study of patency of minor duodenal papilla--comparison between pigment method combined with pH sensor and pancreatographic method].

We investigated the patency of minor duodenal papilla in 25 cases that had presented normal pancreatogram by using the endoscopic retrograde pancreatographic (ERP) method and a pH sensor-combined indigo carmine pigment method. The pigment method allowed us to classify the function of minor papilla into three types according to pancreatic juice excretion pre- and post-secretin administration (Type I), excretion after secretin administration (Type II), and no excretion even after secretin administration (Type III). Twelve cases belonged to Type I, 4 cases to Type II and 9 cases to Type III. By ERP method, terminal shapes of the Santorini's duct were classified as stick type, cystic type and branch type. 19 cases were considered stick type, 2 cases cystic type and 4 cases branch type. Eighteen cases were identified as patent minor papilla under ERP method. There were two cases alleged to be patent under the ERP but without pancreatic juice excretion. Therefore, the necessity of pigment method was confirmed for investigation of the function of minor papilla.

Adult↗

PubMed1991

[Comparison of positivity between density gradient centrifugal method and whole blood method in lymphocyte surface marker analysis with flow-cytometry].

The lymphocyte surface marker analysis with flow-cytometry is usually performed using a density gradient centrifugal method or a whole blood method. We have compared these two methods using several monoclonal antibodies and have found the significant difference in positivity all monoclonal antibodies except TCR-1 (anti alpha/beta receptor on T-lymphocyte). We found the significantly higher positivity of Leu12 and HLA-DR as well as lower of the other monoclonal antibodies by using whole blood method than by density gradient centrifugal method. We conclude that it is necessary to make a distinct description of the method used in the surface marker analysis.

Adult↗

PubMedDate not supplied

Determination of sulfur dioxide in grapes: comparison of the Monier-Williams method and two ion exclusion chromatographic methods.

Results for determination of sulfur dioxide in grapes were compared by 3 methods: the modified Monier-Williams method, acid distillation/ion exclusion chromatography with electrochemical detection (AD/IEC-EC), and alkali extraction/ion exclusion chromatography with electrochemical detection (AE/IEC-EC). An unusual positive response was observed during the later stage of the Monier-Williams distillation of both control grapes and sulfited grapes. Development of volatile acidic compounds in parallel with this Monier-Williams response and darkening of sample was also observed by collection in an alkali trap and analysis using anion exclusion chromatography and photodiode array detection. No parallel increase in sulfite was observed by the more selective AD/IEC-EC method, which clearly demonstrated that the response observed during the later stage of the Monier-Williams method is a false positive, probably due to caramelization reaction products. Monier-Williams results for grapes containing ca 10 ppm sulfite were in reasonably good agreement with those by either the AD/IEC-EC or AE/IEC-EC methods, presumably because the false positive response in the Monier-Williams analysis compensated for the somewhat incomplete recovery of sulfite. The AE/IEC-EC method is recommended because it is rapid, sensitive, straightforward, and free from interference. Accurate results by Monier-Williams analysis could be obtained by limiting distillation to 60 min and correcting for recovery.

Chromatography, Liquid↗

PubMed1990

Total and direct-reacting bilirubin values by automated methods compared with liquid chromatography and with manual methods for determining delta bilirubin.

This study compares total and direct-reacting bilirubin values in 40 serum samples from patients with various diagnoses, as measured by automated methods (Beckman Synchron CX-5, Beckman Astra 8, Kodak Ektachem 700) and HPLC and by a manual method for delta bilirubin. For total bilirubin, within-run CVs were less than 6%. The Ektachem 700 method underestimated bilirubin with serum samples from patients with Crigler-Najjar syndrome and from newborns in whom unconjugated bilirubin concentrations were increased but conjugated bilirubins were not present or were present only in small amounts. The Astra 8 and Synchron CX-5 methods were inaccurate with cholestatic serum samples, in which conjugated bilirubin concentrations were increased and other compounds such as bile acids could be expected to interfere. We conclude that each automated method examined provides reasonable estimates for total and direct-reacting bilirubin values for routine clinical use. The need for each laboratory to select the appropriate bilirubin method for its particular situation is obvious.

Autoanalysis↗

PubMedDate not supplied

Methods of analysis for toxic elements in food products. 3. Limit of determination of methods for assuring safety.

To evaluate the suitability of the analytical methods used in determining food safety, a new metrological characteristic "MQS" is suggested. MQS is defined as the absolute minimum quantity in micrograms of a substance that can be determined in a test solution (solubilized test portion). MQS accounts for 2 factors: (a) the necessity for a reliable determination of ML (maximum permitted level, i.e., regulatory tolerance), and (b) the optimum quantity of test portion of a food product to be analyzed, and thus assists in evaluating the suitability of a method to assure food safety. The MQS of 8 toxic elements in any food are As, 3; Cd, 0.5; Cu, 20; Fe, 50; Hg, 0.2; Pb, 4; Sn, 200; Zn, 100 micrograms. To characterize the applicability of any given method, the specific minimum limit of determination, MQSM, must be established for each method. The method in question may be used to control food safety only if MQSM is less than MQS. MQSM values are given for the common polarographic and colorimetric methods for determining these elements.

Food Analysis↗

PubMed1986

[Hemodynamic change in the liver following hepatic resection in the dog. A comparative study by the 198Au colloid method, KICG and the H2 clearance method].

On the basis of our hypothesis that blood flow in the residual hepatic parenchyma is a determinant factor of posthepatectomy liver function, measurements were made of blood flow in the residual liver after 40% hepatic resection in dog. Adult mongrel dogs were divided into two groups, i.e., normal control and 40% hepatectomy, and evaluated for hepatic hemodynamics by 198Au colloid method, KICG and H2 clearance method. Blood biochemistry and, histology of the liver were also examined. The results are as follows: In the control group, hepatic blood flow by 198Au colloid method, KICG and H2 clearance method was found to correlate significantly with each other. In the 40% hepatectomy group, the hepatic blood flow index by both 198Au colloid method and KICG decreased in proportion to the amount of resected hepatic tissue initially and then increased as the liver regenerated. H2 clearance method showed that hepatic blood flow per unit weight of tissue decreased in the face of reduced hepatic volume in early stage of posthepatectomy period and returned to the preoperative level as the liver regenerated.

Alanine Transaminase↗

PubMed1977

[Assessment of bacterial counts in the meat-processing industry. II. The plate-loop method and the droplet method (author's transl)].

Two methods used in making bacterial counts of meat and surfaces are discussed. When the plate-loop method is used, dilutions are prepared with calibrated loops in spotting tiles. These loops are also used to swab droplets of these dilutions on quadrants of previously dried agar plates. A formula is presented, which may be used in calculating bacterial counts. When the droplet method is adopted, an apparatus is used to prepare dilutions in tubes containing liquid agar. Drops of agar then are transferred into empty Petri dishes by this apparatus. After incubation, the colonies which have grown in these droplets are counted by a viewer included in the apparatus. Both the plate-loop method and the droplet method (if slightly modified) were found to satisfy the criteria simplicity, reliability and saving time and material. This only holds good when accurate counts are made and when bacterial counts are more than 2,500 bacteria per gram or per sq. cm. When these conditions are complied with, the two methods are suited for routine studies of large numbers of samples.

Animals↗

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↗