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PubMed2005

Performance characteristics of four automated natriuretic peptide assays.

Measurement of circulating B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) can identify patients with heart failure and guide therapy. The limit of detection, linearity, imprecision, method comparison, analytic concordance, and reference intervals of the Access 2 BNP (Biosite, San Diego, CA), ADVIA Centaur BNP (Bayer Diagnostics, Tarrytown, NY), AxSYM BNP (Abbott Diagnostics, Abbott Park, IL), and E170 NT-proBNP (Roche Diagnostics, Indianapolis, IN) methods were evaluated. The Triage meter BNP assay (Biosite) was the comparison method. Imprecision testing showed total coefficients of variation of 4.1%, 4.4%, 5.5%, and 0.8% for the Access 2, ADVIA Centaur, AxSYM, and E170, respectively. Relative to the Triage meter, method comparison revealed a slope of 0.96 and r = 0.95, a slope of 0.77 and r = 0.92, a slope of 1.13 and r = 0.94, and a slope of 8.8 and r = 0.80 for the Access 2, ADVIA Centaur, AxSYM, and E170, respectively. Overall analytic concordance values with the Triage meter were 95.9%, 92.9%, 92.4%, and 84.3% for the Access 2, ADVIA Centaur, AxSYM, and E170, respectively. All automated natriuretic peptide methods showed acceptable analytic performance.

Autoanalysis↗

PubMed2003

Selecting outcomes measures in children's rehabilitation: a comparison of methods.

OBJECTIVE: To evaluate the effects of using a computerized self-directed software program, All About Outcomes, to facilitate decisions about the most appropriate outcome measures to use in specific pediatric rehabilitation scenarios. DESIGN: A randomized controlled trial using a crossover design to test the accuracy, time, and ease of use of the decision-making outcome software in selecting 3 potential clinical outcome measures for each of 2 clinical scenarios. SETTING: The trial was conducted in a university school of rehabilitation science in Ontario, Canada. PARTICIPANTS: Thirty student occupational therapists and physiotherapists enrolled at the university participated in the trial. INTERVENTIONS: Six clinical scenarios were created and paired into 3 sets with similar levels of difficulty. Participants were randomly assigned to select the 3 most appropriate outcome measures for 2 scenarios in 1 of the 3 sets by using the library or the software program. The order of the method of searching was randomized to control for order effect. MAIN OUTCOME MEASURES: Accuracy in identifying appropriate outcome measures, time for the search, ease of searching, and satisfaction with the search process were measured for all participants. Accuracy was rated by 2 independent raters who were unaware of the search method used to identify the outcome measures. RESULTS: In comparison to the library search method, the software search method was significantly more accurate, took less time, and was rated as easier in identifying appropriate outcome measures for the clinical scenarios. Users were also significantly more satisfied with the software searching method. The accuracy of the software method was not affected by whether participants used it first or second. However, the accuracy of the library search method improved if it was used after the software method. CONCLUSIONS: Software improved the accuracy and ease of identifying outcome measures for rehabilitation students. Further research is needed to evaluate whether identifying appropriate measures leads to an increased use of outcome measures in clinical practice.

Child↗

PubMed1996

Simultaneous measurement of total hemoglobin and its derivatives in blood using CO-oximeters: analytical principles; their application in selecting analytical wavelengths and reference methods; a comparison of the results of the choices made.

Optical methods of quantifying total hemoglobin (tHb), applying the principles of the Lambert-Beer law, have been used both on untreated whole blood and on blood mixed with chemicals to form a stable chromophore, since the earliest days of laboratory medicine. The same principles may be applied for quantitation of the individual hemoglobin derivatives, such as oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb)1, as well as the non-oxygen transporting "dyshemoglobins", including carboxyhemoglobin (COHb) and methemoglobin (MetHb). The total hemoglobin measurement is typically carried out using a light source with a broad band of visible wavelengths. However, measurement of the derivatives requires using discrete, narrow bands of light in order to differentiate between the small differences of light absorbed by the individual derivatives. Either general-purpose, narrow band-pass spectrophotometers, or special-purpose photometers utilizing a set of fixed wavelengths, commonly referred to as "CO-oximeters" are suitable. Rapid, direct, photometric quantification of the derivatives, necessary in the clinical environment, relies on the specific light absorption characteristics of each hemoglobin derivative at the wavelengths selected, which in turn requires independent and exact knowledge of the concentrations of each entity in reference materials. This report examines the process involved in the selection of wavelengths and reference methods, contrasts the effects of the choices made and discusses some implications and limitations for routine measurement.

Carbon Monoxide↗

PubMed2002

Comparison of methods for identification of Pneumocystis carinii in bronchoalveolar lavage fluid.

Pneumocystis carinii pneumonitis in one of the most common life-threatening opportunistic infections in patients with AIDS. The definitive diagnosis of this infection can be established only by demonstration of the organism in clinical specimens. This study was a comparison of methods that provide easy recognition of the organism which is readily available, simple and can be performed rapidly in laboratory-diagnosis. Bronchoalveolar lavage fluids obtained from 35 AIDS patients suspected of having Pneumocystis carinii pneumonitis were examined by three staining methods for the presence of Pneumocystis carinii. With Giemsa stains, P. carinii could be identified in 18 cases (51.4%). Three developmental stages: "cyst", "sporozoite" and "trophozoite" were seen. The contrast of organisms against host cells was not outstanding in these stains. Toluidine blue O stains provided easy recognition of the organisms, with marked contrast between the cysts and host cells. 21 cases (60%) were positive in these stains, but the intracystic structures and trophozoites could not be identified. It was suggested that the clinical specimen should be stained first with toluidine blue O which is more rapid and permits easy recognition of the cyst clusters. If the sporozoites and trophozoites had to be identified, Giemsa stains can be made. In addition, with the methenamine silver nitrate stains, 21 cases (60%) were positive. They revealed the morphology as seen with toluidine blue O but the cost of material may make it unavailable in many laboratories especially with the budgetary restraints of developing countries.

AIDS-Related Opportunistic Infections↗

PubMed2003

Comparison of methods to identify individuals at increased risk of coronary disease from the general population.

OBJECTIVES: To evaluate the guidelines on measurement of cholesterol in the national service framework for coronary heart disease and to compare alternative strategies for identifying people at high risk of coronary disease in the general population. DESIGN: Comparison of methods (national service framework criteria, Sheffield tables, age threshold of 50 years, estimated risk assessment using fixed cholesterol values) for identifying people with a 10 year coronary event risk of 15% or greater. SETTING: Health survey for England 1998. SUBJECTS: 6307 people aged between 30 and 74 years with no history of myocardial infarction, stroke, or angina. MAIN OUTCOME MEASURES: Proportion of the total population selected for measurement of cholesterol and proportion of people at 15% or greater risk identified. RESULTS: The national service framework guidelines selected 43.4% (95% confidence interval 42.2% to 44.6%) of the study population for cholesterol measurement and identified 81.2% (80.2% to 82.2%) of those at 15% or greater risk. The Sheffield tables selected 73.1% (72.0% to 74.2%) for cholesterol measurement and identified 99.91% (99.83% to 99.99%) of those at 15% or greater risk. An age threshold of 50 years selected 46.3% (45.1% to 47.5%) for cholesterol measurement and identified 92.8% (92.1% to 93.4%) of those at 15% or greater risk. Estimated risk assessments using fixed cholesterol values selected 17.8% (16.8% to 18.7%) for cholesterol measurement and identified 75.9% (74.8% to 76.9%) of those at 15% or greater risk. CONCLUSION: Measuring the cholesterol concentration of everyone aged 50 years and over is a simple and efficient method of identifying people at high risk of coronary disease in the general population.

Adolescent↗

PubMed1982

Comparison of methods of measuring cardiac output in newborn lambs.

To define agreement between methods, we measured cardiac output (CO) in chronically instrumented lambs by four different methods. In 23 lambs we measured CO simultaneously by the Fick and microsphere methods and with an electromagnetic flowmeter over a wide range of CO (80-454 ml/kg/min) in different experimental conditions on 97 occasions. When the electromagnetic flowmeter was corrected for coronary flow (about 8% of CO) calculated from microspheres, the mean cardiac outputs were almost identical for these three methods (237, 235, and 236 ml/kg x min, respectively). Comparisons between any two of the methods showed a correlation coefficient greater than 0.89. In four lambs, 52 measurements of CO by Fick and thermodilution had a correlation coefficient of 0.94. We conclude that any of the four methods, if appropriately applied, adequately measures CO in a variety of circumstances and may be used with confidence for physiologic or other studies.

Animals↗

PubMed2005

Assessment of trueness of glucose measurement instruments with different specimen matrices.

BACKGROUND: The trueness of glucose monitors is commonly assessed using whole-blood samples and a clinical analyzer as a comparison method. In this study, the effect of specimen matrix on trueness of one clinical analyzer and one glucose monitor was compared with a gas chromatography-mass spectrometry (GC/MS) reference method, using split-sample comparison with capillary whole blood (CWB), venous whole blood (VWB), and plasma (PL). METHODS: CWB was analyzed by the glucose monitor and the GC/MS reference method. VWB was analyzed by the glucose monitor, clinical analyzer, and the GC/MS method. PL was analyzed by the clinical analyzer and the GC/MS reference method. RESULTS: For the glucose monitor, the bias was 0.4% and -18.2% for CWB and VWB, respectively. The clinical analyzer had a bias of -25.4% for VWB and -12.0% for PL and a proportional bias was detected in both specimens. Using the clinical analyzer as a comparison method, the glucose monitor had a proportional bias of -9.8%. CONCLUSION: The trueness of clinical analyzers can be affected by the specimen matrix that needs to be assessed before they are used as comparison method to assess trueness of glucose monitors.

Blood Glucose↗

PubMed1984

A comparison of methods for the extraction of nucleoprotein complexes from SV40-infected cells.

A comparison was made between two alternative methods for the nuclear extraction of Simian virus 40 (SV40) virions and nucleoprotein complexes (NPCs) from SV40-infected TC7 cells. The low-salt hypotonic method of Su and DePamphilis (1976) was compared with the detergent method of Garber et al. (1978), since other methods had been shown to result in virion breakdown. There was no disruption of mature SV40 virions with either of these extraction procedures. There was, however, considerably more effective extraction of SV40 NPCs, known to contain large tumor (T) antigen, using the low-salt hypotonic method as opposed to the detergent method. Thus, the low-salt hypotonic method for extraction should be the method of choice when studying SV40 DNA replication or the function of SV40 T antigen in SV40 nucleoprotein complexes.

Antigens, Viral, Tumor↗

PubMed1998

[Comparison of methods to test the "in vitro" cytotoxicity of biocompatible materials].

OBJECTIVE: A comparison of the sensitivity of the agar diffusion method with that of extraction using cell-lines RC-IAL (fibroblastic of rabbit kidney) and HeLa (epithelial carcinoma cells from the cervix uteri of the human uterus), in the in vitro evaluation of materials of medical and hospital. MATERIALS AND METHODS: Fifteen samples chosen at random, from among the already known positives and negatives in our stock, were tested and identified as cotton, form, latex, cellulose and acrylic. Besides the samples mentioned, many SDS (GIbco) concentrations were tested experimentally in RC-IAL and HeLa cell cultures. RESULTS: Of the 50 samples tested, 44(88%) were positive by both methods. However, when the SDS were compared by using the two methods, positive results were noted in the concentrations of from 0.5 to 0.05 microgram/ml in the agar diffusion ans extraction methods. A cytotoxic effect was only noted in the concentrations of up to 0.25 microgram/ml. CONCLUSION: When the SDS was used, differences favorable to the agar diffusion method were observed in the two cell lines, in two concentrations; that is, the sensitivity of this method was quantitatively greater on inspection than that of the extraction method, as well as being the simpler method to use.

Animals↗

PubMed2000

Comparison of methods for isolating Salmonella bacteria from faeces of naturally infected pigs.

A series of experiments was conducted using faecal samples collected from commercial swine farms to evaluate the effects of variation in methods used for the detection of Salmonella bacteria. The primary objective of the studies was to compare the protocols routinely used in two laboratories in the USA. The studies included five experiments comparing the enrichment protocols used routinely in the respective laboratories (Method 1: 10 g faeces--buffered peptone water (BPW) pre-enrichment--selective enrichment in Rappaport/Vassiliadis (RV) broth; Method 2: approximately 1g faeces--primary enrichments in tetrathionate and Hajna GN broths--secondary enrichment in RV broth). The effects of enrichment temperatures (37 vs 42 degrees C) using RV broth (two experiments) and delayed secondary enrichment (four experiments) were also evaluated. Direct comparison of Method 1 and Method 2 indicated comparable results. However, when compared using faecal samples of equal weight, the Method 2 enrichment protocol was more sensitive for detecting Salmonella bacteria than the Method 1 protocol. Enrichment in RV at 42 degrees C was superior to 37 degrees C, particularly for samples that were pre-enriched in BPW. Delayed secondary enrichment increased detection of Salmonella bacteria in swine faeces. These results highlight the imperfect sensitivity of culture methods, and the need for researchers to consider the sensitivity of bacteriological methods in the design and interpretation of the results of epidemiologic studies based on faecal culture.

Animals↗

PubMed1995

Comparison of methods for searching protein sequence databases.

We have compared commonly used sequence comparison algorithms, scoring matrices, and gap penalties using a method that identifies statistically significant differences in performance. Search sensitivity with either the Smith-Waterman algorithm or FASTA is significantly improved by using modern scoring matrices, such as BLOSUM45-55, and optimized gap penalties instead of the conventional PAM250 matrix. More dramatic improvement can be obtained by scaling similarity scores by the logarithm of the length of the library sequence (In()-scaling). With the best modern scoring matrix (BLOSUM55 or JO93) and optimal gap penalties (-12 for the first residue in the gap and -2 for additional residues), Smith-Waterman and FASTA performed significantly better than BLASTP. With In()-scaling and optimal scoring matrices (BLOSUM45 or Gonnet92) and gap penalties (-12, -1), the rigorous Smith-Waterman algorithm performs better than either BLASTP and FASTA, although with the Gonnet92 matrix the difference with FASTA was not significant. Ln()-scaling performed better than normalization based on other simple functions of library sequence length. Ln()-scaling also performed better than scores based on normalized variance, but the differences were not statistically significant for the BLOSUM50 and Gonnet92 matrices. Optimal scoring matrices and gap penalties are reported for Smith-Waterman and FASTA, using conventional or In()-scaled similarity scores. Searches with no penalty for gap extension, or no penalty for gap opening, or an infinite penalty for gaps performed significantly worse than the best methods. Differences in performance between FASTA and Smith-Waterman were not significant when partial query sequences were used. However, the best performance with complete query sequences was obtained with the Smith-Waterman algorithm and In()-scaling.

Algorithms↗

PubMed2005

Standardization of HbA1c and Optimal Range of Monitoring.

The IFCC has established a working group on HbA1c standardization, which developed a reference system to act as basis for global standardization of all glycohemoglobin/HbA1c assays. The reference system is based on HbA1c, defined as beta-N-1-deoxy fructosyl haemoglobin as component. Two reference methods specifically measure the glycated N-terminal residue of the beta chain of haemoglobin. The assay principle is peptide mapping after proteolytic cleavage of the molecule followed by measurement of the ratio of the glycated and non-glycated ss-N-terminal hexapeptides by HPLC/MS or HPLC/CE. An international network of 12 reference laboratories is in place. An overall CV below 2% is achieved in comparison studies, which guarantees a reliable value assignment to secondary reference materials. For implementation of the system, the relationship between IFCC and the existing Designated Comparison Methods in the US (NGSP), Sweden (MonoS) and Japan was calculated in seven method comparisons. In all cases, the correlation was exactly the same, making recalculation of the various systems to one IFCC reference system possible. IFCC values will be a reference range of 3-4% HbA1c with a target value of optimal treatment of 5% and change of therapy proposed at values >6%. The last item of the IFCC WG on HbA1c standardization is the adjustment of all the commercial methods to this new reference system. Three method comparison studies with all the major manufacturer methods were performed. This allowed us to first anchor all commercial methods to the IFCC reference system and thereafter recalculate the results to the new IFCC system. Secondary reference materials and a transfer protocol are provided to enable manufacturers to adjust their routine tests to the new reference system. The IFCC reference system for HbA1c will make it possible to improve the performance of routine HbA1c assays. The goal of this improved analytical performance is a within and between run CV of 2%. If this can be achieved, then the HbA1c results can be incorporated into the diagnostic strategies for detecting diabetes mellitus.

Blood Chemical Analysis↗

PubMed2006

Feasibility of standardization of serum C-peptide immunoassays with isotope-dilution liquid chromatography-tandem mass spectrometry.

BACKGROUND: Serum C-peptide concentrations reflect pancreatic function in different clinical and diagnostic settings; however, the utility of C-peptide testing is limited by the lack of standardized commercial immunoassays. Standardization can best be done by split-sample comparison with a hierarchically higher reference measurement procedure with a set of native sera. For serum peptides, isotope-dilution liquid chromatography-mass spectrometry (ID-LC/MS) is recommended as a reference measurement procedure. METHODS: We evaluated the analytical performance characteristics of an ID-LC/tandem MS procedure for measurement of serum C-peptide after a 2-step solid-phase extraction. To investigate the feasibility of this procedure for use in standardization, we also performed a method comparison with 3 representative commercial assays. RESULTS: The ID-LC/tandem MS procedure showed maximum within-run, between-run, and total CVs on dedicated sera (C-peptide concentrations, 1.6 and 4.0 mug/L) of 2.1%, 2.5%, and 2.9%, respectively; an accuracy of 94.6%-104.1%; a minimum trueness of 98.1% (95% confidence interval, 96.2%-100.0%), and limits of quantification and detection of 0.15 and 0.03 mug/L, respectively. Deming linear regression analysis of the method-comparison data showed that the immunoassays correlated well with ID-MS and were specific, but lacked intercomparability and trueness. We propose that the deficiencies can be resolved by recalibration on the basis of the method comparison. CONCLUSIONS: The ID-LC/tandem MS procedure is suitable for specific and accurate measurement of basal and stimulated serum concentrations of proinsulin C-peptide fragment 33-63 and is suitable for use in standardization of C-peptide immunoassays.

Adolescent↗

PubMed1975

A comparison of methods for the measurement of cardiac output and blood oxygen content.

A comparison has been made between the recently introduced thermal dilution method for measurement of cardiac output and the standard dye dilution technique. Two relatively new methods of measurement of blood oxygen content, one involving the measurement of oxygen tension after release of oxygen by carbon monoxide, and the other the measurement of current flow upon reduction of oxygen in a galvanic cell, have been compared with a standard indirect method of measurement of blood oxygen content. All three new methods fulfilled the criteria of accuracy and simplicity and compared favourably with the standard methods. Of the two new methods for measurement of oxygen content, that involving reduction of oxygen in a galvanic cell was superior by virtue of compactness and speed of operation.

Animals↗

PubMed1996

Detection of genes coding for extended-spectrum SHV beta-lactamases in clinical isolates by a molecular genetic method, and comparison with the E test.

A highly sensitive and specific method, termed PCR/NheI, for the detection of genes coding for SHV extended-spectrum beta-lactamases (ESBL) in clinical isolates is presented. It is based on polymerase chain reaction (PCR) amplification of the blaSHV genes, followed by restriction with NheI. Due to the glycine (positive 238) (SHV-non-ESBL)-->serine (position 238) (SHV-ESBL) mutation, only PCR fragments from the genes coding for SHV-ESBLs were cleaved. A commercially available test for ESBLs, the E test ESBL, identified 52% of our 29 clinical isolates carrying blaSHV-ESBL genes as ESBL producers.

Base Sequence↗

PubMed1976

Electroencephalogram spectral analysis by the direct and indirect methods: a comparison.

An artificially-created electroencephalogram was used to perform a comparison between the indirect and direct analysis methods. The results obtained by Fourier transform of the correlation function and smoothing of Fourier series development differ for a stochastic process in which the correlation functions are not sufficiently damped. Some mathematical framework is also appended in which the difference is worked out from a more theoretical point of view. In order to obtain results independent of inherent conditions, which in the simplest way can be detected by calculating the correlation functions, the indirect method is preferable.

Brain↗

PubMed2003

Semiautomated segmentation of blood vessels using ellipse-overlap criteria: method and comparison to manual editing.

Two-dimensional intensity-based methods for the segmentation of blood vessels from computed-tomography-angiography data often result in spurious segments that originate from other objects whose intensity distributions overlap with those of the vessels. When segmented images include spurious segments, additional methods are required to select segments that belong to the target vessels. We describe a method that allows experts to select vessel segments from sequences of segmented images with little effort. Our method uses ellipse-overlap criteria to differentiate between segments that belong to different objects and are separated in plane but are connected in the through-plane direction. To validate our method, we used it to extract vessel regions from volumes that were segmented via analysis of isolabel-contour maps, and showed that the difference between the results of our method and manually-edited results was within inter-expert variability. Although the total editing duration for our method, which included user-interaction and computer processing, exceeded that of manual editing, the extent of user interaction required for our method was about a fifth of that required for manual editing.

Aneurysm↗

PubMedDate not supplied

[Salmonella: comparison of methods for its detection in bird feed].

The Gene Trak colorimetric hybridization method (GENE TRAK Systems, 31 New York Avenue, Framingham, M.A.) was compared with conventional methodology proposed by International Commission for Microbiological Standard Foods (ICMSF) for the detection of Salmonella in samples of broiler feed and raw materials of vegetal and animal origin used in its formulation. In this study 249 samples which included inoculated samples and 9 uninoculated samples were studied. On 240 uninoculated samples, 62.9% resulted free of Salmonella, 27.9% were positive for both methods and 9.2% were positive by Gene Trak but it couldn't be confirmed by conventional methodology after five determinations. This methodology is presented as an interesting method of screening with important advantages in comparison to conventional methodology: facility for processing a big number of samples with few material expenses, less time to get results and high sensibility.

Animal Feed↗