[Modification of chemical components of the blood by specimen collection methods. A comparison between vacuum collection and standard collection methods].
Explore the source record for details and available documents.
Blood Chemical Analysis↗
SEARCH · PubMed Health
Results for “method comparison”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Casting force in several casting methods. 2. Comparison of casting time in several casting methods.
Explore the source record for details and available documents.
Dental Casting Technique↗
[Failed postpartum sterilisation--a comparison of 5 methods].
A comparison of the standard Vienna method of postpartum sterilisation (3,580 patients with 18 failures and a sterilisation failure rate of 5.03/1,000) with 4 other methods at Paarl Hospital is presented: the Pomeroy method (892 patients with 19 failures and a sterilisation failure rate of 21.31/1,000); the total fimbriectomy method (1,578 patients with 23 failures and a sterilisation failure rate of 14.58/1,000); the Filshie clip method (808 patients with 18 failures and a sterilisation failure rate of 22.28/1,000); and the Irving method performed at caesarean section (456 patients and 1 failure). As no totally permanent technique exists to prevent pregnancy, a plea is lodged for legalised abortion after failed sterilisation.
Female↗
Digital signal processing methods for biosequence comparison.
A method is discussed for DNA or protein sequence comparison using a finite field fast Fourier transform, a digital signal processing technique; and statistical methods are discussed for analyzing the output of this algorithm. This method compares two sequences of length N in computing time proportional to N log N compared to N2 for methods currently used. This method makes it feasible to compare very long sequences. An example is given to show that the method correctly identifies sites of known homology.
Algorithms↗
Attenuation correction of myocardial SPECT perfusion images with low-dose CT: evaluation of the method by comparison with perfusion PET.
UNLABELLED: In cardiac SPECT, specificity is significantly affected by artifacts due to photon absorption. As the success of attenuation correction depends mainly on high-quality attenuation maps, SPECT low-dose CT devices are promising. We wanted to evaluate the usefulness of a SPECT low-dose CT device in myocardial perfusion scintigraphy. For the evaluation of attenuation correction systems, primarily comparisons with coronary angiography are used. Because the comparison of a method showing myocardial perfusion with an investigation displaying the morphology of vessels yields some difficulties, we chose perfusion PET with (13)N-ammonia as the reference method. METHODS: We prospectively analyzed 23 patients (6 women, 17 men) with known or suspected coronary artery disease. Rest studies and studies under pharmacologic stress with adenosine were performed. After simultaneous injection of (13)N-ammonia and (99m)Tc-sestamibi, a dynamic PET acquisition was started. The SPECT study was performed about 2 h later. Based on 20-segment polar maps, SPECT with and without attenuation correction was compared with PET-derived perfusion values and ammonia uptake values. The PET uptake images were also smoothed to adjust their resolution to the resolution of the SPECT images. RESULTS: The concordance of SPECT and PET studies was improved after attenuation correction. The main effect was seen in the inferior wall. Especially in the apex and anterolateral wall, there were differences between SPECT and PET studies not attributable to attenuation artifacts. Because these differences diminished after smoothing of the PET studies, they might be due to partial-volume effects caused by the inferior resolution of the SPECT images. CONCLUSION: The x-ray-derived attenuation correction leads to SPECT images that represent myocardial perfusion more accurately than nonattenuation-corrected SPECT images. The benefit of the method is seen primarily in the inferior wall. The low resolution of the SPECT system may lead to artifacts due to partial-volume effects. This phenomenon must be considered when perfusion PET is used as a reference method to investigate the effect of attenuation correction.
Adult↗
Technology assessment in critical care: understanding statistical analyses used to assess agreement between methods of clinical measurement.
Many new measurement methods that employ various technologies to measure physiological parameters have been introduced into the field of critical care. Clinical assessment of these new methods occurs through the conduct of method-comparison studies in which the level of agreement between a new measurement method and a clinical standard method is determined. Clinicians and researchers are often faced with the complicated task of analyzing and interpreting the results of method-comparison studies. Use of correlation and linear regression techniques has been prevalent in method-comparison studies but has proven inappropriate and inadequate in determining how well methods compare. The purposes of this article are to briefly review the terms of accuracy, agreement, and the precision in context with method-comparison studies, and discuss inappropriate and appropriate statistical analyses and their interpretation. Appropriate data analysis of method-comparison studies will aid in determining not only whether new monitoring methods can be interchanged or used in place of existing methods, but whether new methods warrant further research of their effect on patient outcomes.
Critical Care↗
Graphic representation of data resulting from measurement comparison trials in cataract and refractive surgery.
BACKGROUND AND OBJECTIVES: The evaluation of new diagnostic measurement devices allows intraindividual comparison with an established standard method. However, reports in journal articles often omit the adequate incorporation of the intraindividual design into the graphic representation. PATIENTS AND METHODS: This article illustrates the drawbacks and the possible erroneous conclusions caused by this misleading practice in terms of recent method comparison data resulting from axial length measurement in 220 consecutive patients by both applanation ultrasound and partial coherence interferometry. RESULTS: Graphic representation of such method comparison data should be based on boxplots for intraindividual differences or on Bland-Altman plots. Otherwise, severe deviations between the measurement devices could be erroneously ignored and false-positive conclusions on the concordance of the instruments could result. CONCLUSION: Graphic representation of method comparison data should sensitively incorporate the underlying study design for intraindividual comparison.
Cataract↗
Comparison of cation-adjusted Mueller-Hinton broth with Iso-Sensitest broth for the NCCLS broth microdilution method.
Comparison of MIC results obtained in different parts of the world is currently difficult because of variations in methods. In this study, cation-adjusted Mueller-Hinton broth, the NCCLS-recommended medium, was compared with Iso-Sensitest broth, which is widely used in Europe. Microbroth dilution testing, using the NCCLS procedure, was performed on 124 Gram-positive (staphylococci and enterococci) and Gram-negative (Enterobacteriaceae and Pseudomonas aeruginosa) isolates from the CDC reference set, with the only variable being the medium used. Twelve antimicrobial agents were tested: amoxycillin-clavulanic acid, ampicillin, ciprofloxacin, erythromycin, gentamicin, imipenem, levofloxacin, oxacillin, gemifloxacin, trimethoprim- sulphamethoxazole, tetracycline and vancomycin. Vancomycin, erythromycin and oxacillin were only evaluated for the Gram-positive organisms. Trimethoprim-sulphamethoxazole was only evaluated for a subset of Gram-negative organisms because of off-scale results. The 124 isolates were tested in one American and one UK laboratory with two batches of cation-adjusted Mueller-Hinton broth and two of Iso-Sensitest broth. A statistical evaluation of the data used a 24 fully specified factorial analysis to determine if there were significant differences in results owing to Gram reaction, site of testing and type and/or batch of broth. In addition, the cumulative results for each antimicrobial agent in each broth were plotted against the range of MIC dilutions tested. MICs of ciprofloxacin, levofloxacin, gemifloxacin, gentamicin and tetracycline were slightly higher (half a doubling dilution) with Iso-Sensitest broth than with Mueller-Hinton broth. MIC results for the other antimicrobial agents were equivalent. Essential and category agreement rates were comparable for all agents (88.4-100% and 88.2-99.0%, respectively).
Anti-Bacterial Agents↗
Calculating expected deaths: a comparison of two methods.
A comparison is presented between the traditional "person-years" and more recently described "prospective model" methods for calculating mortality expectations. Problems arising from the fact that expectations under the person-years method are calculated on the basis that a null hypothesis is true, which results in artificial figures that, at least theoretically, are meaningless if the hypothesis is rejected, are discussed. Data are presented from two studies in which expectations have been calculated both ways, showing important differences between the two methods with an exaggeration of the expectation when the study group has an above normal mortality experience. It is suggested that the person-years methodology should be replaced by that of the prospective model.
Actuarial Analysis↗
STAR gene restriction profile analysis in epidemiological typing of methicillin-resistant Staphylococcus aureus: description of the new method and comparison with other polymerase chain reaction (PCR)-based methods.
A method based on restriction profile analysis of the STAR repetitive element PCR (STAR-RP PCR) product obtained by digestion with AluI and Tru9I was developed for typing methicillin resistant Staphylococcus aureus (MRSA). We evaluated a well defined collection of MRSA from Argentina, previously characterized by PFGE (pulsed field gel electrophoresis) of chromosomal SmaI digests and hybridization with DNA probes for probes ClaI-mecA and ClaI-Tn554. We comparatively evaluated STAR-RP analysis with other PCR based methods such as Inter IS256-PCR, Rep-MP3 PCR and Coa-RP. The discriminatory power (D) of STAR-RP (0.86) was similar to that of PFGE (0.84) at the type level. Comparable results were obtained with Inter IS256 PCR (0.85) and Rep-MP3 PCR (0.80). A lower value (0.74) was obtained for Coa-RP. An excellent reproducibility (100%) of STAR-RP was observed. Good concordance between STAR-RP and other molecular typing methods was found for MRSA isolates (n = 39). STAR-RP typing showed 87% concordance with mecA::Tn554::PFGE, 87% with Inter IS256 PCR and 71% with Rep-MP3 typing. STAR-RP is suggested as an adequate molecular typing assay for MRSA epidemiologic assessment.
Argentina↗
Quantification and interpretation of total petroleum hydrocarbons in sediment samples by a GC/MS method and comparison with EPA 418.1 and a rapid field method.
Total petroleum hydrocarbons (TPH) as a lumped parameter can be easily and rapidly measured or monitored. Despite interpretational problems, it has become an accepted regulatory benchmark used widely to evaluate the extent of petroleum product contamination. Three currently used methods (GC/MS, conventional EPA 418.1, and a rapid field method PetroFLAG) were performed to quantify the TPH content in samples collected from a site contaminated by transformer oil. To standardize the method and improve the comparability of TPH data, crucial GC-based quantification issues were examined, e.g., quantification based on internal standards (ISTD) vs external standards (ESTD), single vs multiple ISTD, and various area integration approaches. The interpretation of hydrocarbon chromatographic results was examined in the context of field samples. The performance of the GC/MS method was compared with those of EPA 418.1 and PetroFLAG. As a result, it was observed that the ISTD quantification method was preferred to the ESTD method, multiple ISTD might be better than single ISTD, and three different area integration approaches did not have a significant effect on TPH results. Evaluation of the chromatograms between a reference sample and three unknown samples showed that the extent of contamination varied appreciably with sample depth. It was also found that there existed a good positive correlation between GC/MS and both EPA 418.1 and PetroFLAG, and that EPA 418.1 produced the higher overall estimate while GC/MS and PetroFLAG resulted in lower, more statistically comparable TPH values.
Chemistry Techniques, Analytical↗
3-D computation of E fields by the volume-surface integral equation (VSIE) method in comparison with the finite-integration theory (FIT) method.
An algorithm has been developed for calculation of 3-dimensional E fields by the volume-surface integral equation (VSIE) method. Integration over surface elements is performed by elementary analytical formulas, assuming a linear interpolation of surface charges. Grid points at electrical interfaces are split off, well considering the E field behavior at these contours, specifically at sharp bends and multimedia junctions. Averaging procedures are utilized in order to avoid undefined or infinite values at critical points. The VSIE is solved by iteration using GMRES ("general minimum residuum") solver on a SUN workstation SPARC-IPX or Cray XMP, whereby convergence speed decreases considerably as the heterogeneity of the problem increases. Computation time (e.g., 20 min on a supercomputer for approximately 30,000 cells) needs to be reduced by further code development. Results for 3-D test cases (plane wave illuminating a layered cylinder) generally agree well with the finite-integration-theory (FIT) method if high E field gradients occur perpendicular to electrical boundaries. The VSIE method predicts slightly higher E fields only in critical regions. On the other hand, the FIT method at present is more efficient with respect to computation time for large domains with high cell numbers (> 100,000 cells).
Algorithms↗
Performance of predispensed reagent and noncentrifugation methods for high-density lipoprotein cholesterol measurement.
OBJECTIVE: To evaluate the performance of high-density lipoprotein cholesterol methods with predispensed reagent (SPINPRO, ISO Spin, Vitros, and One Shots) and noncentrifugation separation (Magnetic-HDL) compared with traditional high-density lipoprotein cholesterol methods (PBI Plus, Boehringer-Mannheim, and Abbott). DESIGN: Precision was evaluated by running two concentrations of frozen human sera and two concentrations of lyophilized quality control material according to National Committee for Clinical Laboratory Standards document EP5-T2. Accuracy was evaluated by comparing sample results achieved by each method with those by the Cholesterol Reference Method Laboratory Network Designated Comparison Method and the Lipid Research Clinics' heparin-Mn++ method. Sera from donors with high triglyceride levels were used to challenge the ability of each method to measure lipemic samples for each method. SETTING: Outpatient clinic and university medical center. PATIENTS: Forty-two ambulatory donors with high-density lipoprotein cholesterol levels ranging from 30 to 102 mg/dL, cholesterol levels ranging from 107 to 679 mg/dL, and triglyceride levels ranging from 20 to 2450 mg/dL. MAIN OUTCOME MEASURE: Precision, accuracy, linearity, and ability to measure lipemic samples. RESULTS: Imprecision varied from CV 1.4% to 8.6%. The mean absolute bias for each method versus the Designated Comparison Method ranged from 2.6% to 13.3%. Deming regression analysis of all methods versus the heparin-Mn++ method gave slopes from 0.88 to 1.08 and intercepts from -4.5 to 0.0 mg/dL. All methods met the current 22% total error for individual specimens recommended by the National Cholesterol Education Program. Not all methods could measure high-density lipoprotein cholesterol in the presence of high concentrations of triglycerides. CONCLUSIONS: Performance of all methods met the current recommendations of the National Cholesterol Education Program. Not all methods met the 1998 performance goals.
Blood Donors↗
Performance characteristics of a recombinant enzymatic cycling assay for quantification of total homocysteine in serum or plasma.
BACKGROUND: Homocysteine is an amino acid that has been linked to an increased risk of coronary artery disease and stroke. A recombinant enzymatic cycling assay for homocysteine was evaluated using a Roche Modular Analytics P800 chemistry analyzer. METHODS: Bound homocysteine is released by disulfide reduction and combined with serine to form L-cystathionine that is degraded by cystathionine beta-lyase into homocysteine, pyruvate, and ammonia. Pyruvate is converted to lactate and the amount of NAD+ produced is directly proportional to the concentration of homocysteine. The limit of detection (LOD), linearity, imprecision, method comparison, reference interval and susceptibility to common interferences were assessed. RESULTS: The limit of detection was 0.31 micromol/l. The method was linear from 1 to 100 micromol/l with a maximum deviation from the target concentration of <10%. The total imprecision was <5.4% for homocysteine concentrations between 11.4 and 39.4 micromol/l. Method comparison was performed using an immunoassay on the ADVIA Centaur as the comparison method. Deming regression analysis gave a slope of 1.00, intercept of -0.75 and r=0.992. The mean bias relative to the ADVIA Centaur method was -0.9 micromol/l with limits of agreement of -5.0 and +3.5 micromol/l. The reference interval was 4.7 to 12.7 micromol/l. CONCLUSIONS: This enzymatic assay for homocysteine provides acceptable performance on the Modular Analytics P800 analyzer.
Automation↗
Comparison of methods for analyzing binary data arising from two-sample twin studies.
The study of twins is widely used for research into genetic and environmental influences on human outcome measurements. For the study design in which independent samples of monozygotic and dizygotic twins are compared with respect to their similarity on a binary trait, several statistical methods have been proposed. Using a Monte Carlo simulation, we compare the five following procedures: 1) goodness-of-fit method based on the common correlation model, 2) normal approximation of the maximum likelihood estimators of the common correlation coefficients, 3) Ramakrishnan et al. [(1992) Genet Epidemiol 9:273-282] method of odds ratio comparison, 4) generalized estimating equations method of odds ratio estimation, and 5) tetrachoric correlation method. The results show that the goodness-of-fit approach has similar or better performance in both type-one error rates and power than the other methods in all parameter settings. Its advantage with respect to type-one error rates is particularly clear under conditions of small sample sizes, extreme prevalences, or high values of the intraclass correlation coefficients. Therefore, the goodness-of-fit method is recommended for the two-sample twin study design.
Coronary Disease↗
Radioiodination of human low density lipoprotein: a comparison of four methods.
A comparison has been made of four labelling techniques used to radioiodinate human low density lipoprotein (LDL). (1) Chloramine T iodination at pH 7.4 was 20-25% efficient and gave a product immunologically indistinguishable from native LDL. Approximately 30% of the incorporated radioactivity, however, was found in LDL lipids, and the metabolic decay of the labelled complex in rats did not obey first order kinetics. Radiolabelling at pH 10 reduced the uptake of 125I into lipids to 10% but also cut the overall incorporation of radioiodine by a factor of 7. (2) Lactoperoxidase labelling and (3) conjugation with iodinated N-succinimidyl-3-(4-hydroxyphenyl)propionate were highly efficient (100%), but incorporation of radioactivity into the lipid moiety was unacceptably high (approximately 30%). (4) The efficiency of iodine monochloride labelling was highly reproducible and the product was immunologically indistinguishable from native LDL. Incorporation of radioactivity into the lipid moiety was less than 4% when the I/protein ratio of the product was kept at or below 1 : 1. Decay of the radiolabelled LDL in rats was monoexponential.
Animals↗
Partial perfusion in awake neonatal lambs: a comparison of three methods.
A comparison of the effects of extended partial perfusion of conscious lambs was made between the use of a silicone-tube membrane oxygenator and a bubble oxygenator (Infant Temptrol). The survival time of the lambs was markedly shortened with the bubble oxygenator, although much longer than had been anticipated. A serious problem was uncontrollable bleeding from the cannulation wounds with a rapidly declining PCV. In a third group of experiments the suitability of Ancrod (Arvin-extract of the venom from the Malayan Pit Viper) as an anticoagulant for extended perfusion with a membrane oxygenator was assessed. In our hands bleeding from the cannulation wounds was marked and difficult to control. The fall in the haematocrit which accompanied the bubble and the arvin series was rapid and appeared to be greater than may have been expected from the loss alone. The decline in several of the plasma components appeared to be due largely to the fall in the haematocrit. Successful perfusion of conscious lambs for up to 96 hours was possible with a silicone-tube membrane oxygenator with Heparin anticoagulation.
Ancrod↗
Determination of differences in virulence of strains of Salmonella typhosa; a comparison of methods.
An investigation is reported of a comparison by three methods of the degree and certainty of differentiation of strains of S. typhosa of different virulence for mice. These methods were (a) intracerebral injection, (b) intraperitoneal injection of saline suspensions, and (c) intraperitoneal injection of mucin suspensions of the test organisms. With the strains of S. typhosa employed, differentiation was questionable by the intracerebral method, somewhat more marked by the intraperitoneal-saline suspension method, and most definite by the intraperitoneal-mucin suspension method. Differentiation of the strains employed was found to be independent of the presence or absence of Vi antigen and apparently was more dependent upon the method of testing than upon any known differences in biological characteristics of the organisms.
Animals↗