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Results for “Repeatability and Reproducibility”

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At least 253 records · Page 14Linked to original sources

PubMedDate not supplied

Multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in milk by gas chromatography with electron-capture detection after extraction by matrix solid-phase dispersion.

A multiresidue analytical method based on matrix solid-phase dispersion was developed to analyze liquid milk for 22 organochlorine pesticides (OCPs) and 6 polychlorinated biphenyls (PCBs). Initial extraction is performed by loading 3 mL milk onto a 2.0 g octadecyl (C18)-bonded silica cartridge with n-hexane as the eluant. Neutral alumina column chromatography with sodium sulfate as the drying agent is used for further cleanup. The eluate is concentrated to 0.5 mL, and target analytes are determined by capillary gas chromatography with electron-capture detection. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of milk samples fortified at 10 and 1 microg/L levels. Average recoveries were between 74 and 106% for all residues except beta-HCH, beta-endosulfan, and endosulfan sulfate. Both repeatability and reproducibility relative standard deviation values were < 22% for all residues. Detection limits ranged from 0.02 to 0.12 microg/L and quantitation limits were between 0.02 and 0.62 microg/L. The proposed analytical method may be used as a fast and simple procedure in routine determinations of OCPs and PCBs in milk.

Animals↗

PubMed1997

Variability of forces applied by experienced therapists during spinal mobilization.

OBJECTIVE: To determine the variation in forces used by different therapists during mobilization of the lumbar spine and the repeatability and reproducibility of individual therapists. DESIGN: An instrumented mobilization couch was developed to measure the forces applied to the trunk during spinal mobilization. BACKGROUND: Due to limitations in equipment design and data analysis, previous related studies demonstrate equivocal results. METHODS: The system was used to collect data from a sample of 30 experienced therapists to evaluate variation, repeatability and reproducibility during the application of five mobilization procedures. RESULTS: The variation in forces used by different therapists when performing the same technique was substantial, ranging between 63 and 347 N for one technique. During this procedure, 30% of the therapists were found to be relatively consistent, repeating the magnitude of the force applied at the first session within 5%. Others demonstrated considerable variation, exhibiting a difference as great as 34%. CONCLUSIONS: The inconsistency between experienced therapists has considerable implications for clinical practice. Changes in the magnitude and rate of loading are likely to have different effects due to the inherent viscoelastic behaviour of soft tissues. RELEVANCE: Spinal mobilization and manipulation techniques are frequently used by manual therapists in the treatment of musculoskeletal disorders. Despite the reliance on these techniques in clinical practice, there is little scientific evidence to substantiate their use. Before progress in this area can be made, it is necessary to characterize the forces used during typical mobilization procedures. The results can be used to develop teaching strategies and as a basis for comparative research on the efficacy of these techniques.

Journal Article↗

PubMed2006

Determination of toxaphene enantiomers by comprehensive two-dimensional gas chromatography with electron-capture detection.

Comprehensive two-dimensional gas chromatography with micro electron-capture detection (GC x GC-microECD) has been evaluated for the enantioseparation of five chiral toxaphenes typically found in real-life samples (Parlar 26, 32, 40, 44 and 50). From the two enantioselective beta-cyclodextrin-based columns evaluated as first dimension column, BGB-176SE and BGB-172, the latter provided the best results and was further combined with three non-enantioselective columns in the second dimension: HT-8, BPX-50 and Supelcowax-10. The combination BGB-172 x BPX-50 was finally selected because it provided a complete separation among all enantiomers. A satisfactory repeatability and reproducibility of the retention times in both the first and the second dimension were observed for all target compounds (RSDs below 0.8%, n = 4). Linear responses in the tested range of 10-200 pg/microl and limits of detection in the range of 2-6 pg/microl were obtained. The repeatability and reproducibility at a concentration of 100 pg/microl, evaluated as the RSDs calculated for the enantiomeric fraction (EF), was better than 11% (n = 4) in all instances. The feasibility of the method developed for real-life analyses was illustrated by the determination of the enantiomeric ratios and concentration levels of the test compounds in four commercial fish oil samples. These results were compared to those obtained by heart-cut multidimensional gas chromatography using the same enantioselective column.

Animals↗

PubMed2004

Definition of vaginal doses in intrauterine high-dose-rate brachytherapy.

PURPOSE: The aim of this study was to evaluate dosimetric aspects of high-dose-rate (HDR) intrauterine brachytherapy applications and to discuss a possible definition of vaginal points for dose reporting. METHODS AND MATERIALS: HDR brachytherapy was performed using a "Fletcher-like" applicator. Doses to the vaginal mucosa were assessed using 2 sets of points for each ovoid. Fifty treated patients were chosen for the analysis. Repeatability and reproducibility were analyzed. Total doses for the whole treatment at the vaginal points were calculated for each patient. The average dose for both ovoids was determined and the ratio of this dose to the dose at point "A" was calculated. The correlation between delivered doses and vaginal complications was tested statistically. RESULTS: Repeatability and reproducibility were found to be less than 1% compared with patient-to-patient variations (> 99%) for all points. The number of fractions and the number of patients in which the middle ovoid point was "representative" were calculated for the lateral and upper surfaces, respectively. The calculated vaginal-average to point "A" dose ratio was found to be 175% and 130% for the 20 and 25 mm ovoids, respectively. A correlation between delivered doses and the rate of complications was not found. CONCLUSIONS: The proposed method has been validated and allows calculations of vaginal doses. The vaginal-to-point "A" dose ratios allow a fast estimation of the vaginal dose for 20 and 25 mm ovoids. The doses delivered to our patients were below vaginal tolerance.

Antineoplastic Agents↗

PubMedDate not supplied

Isolation of Alicyclobacillus acidoterrestris from fruit juices.

K agar, a novel isolation medium developed for the food industry, was compared with other acidified media for isolation of Alicyclobacillus acidoterrestris spores. Spores were inoculated into apple juice, orange juice, and a fruit juice blend and then isolated on the following media: K agar, pH 3.7; semi-synthetic medium, pH 4.0; orange serum agar, pH 3.5; and minimal salts medium, pH 4.0. Media were incubated at 24, 35, 43, and 55 degrees C. Highest recovery of spores was obtained with either K agar or semi-synthetic medium, incubated at 43 degrees C. The effect of heat shocking spores at different times was also determined; heat shocking at 80 degrees C for 10 min was considered appropriate. Peptone, previously shown to inhibit A. acidoterrestris, was not inhibitory when present in K agar. A collaborative trial with 9 laboratories was undertaken to determine the repeatability and reproducibility of counts on K agar. K agar prepared from individual components was compared with dehydrated K agar prepared by International BioProducts (Redmond, WA). There were no significant differences between log mean counts for the 2 media for each of the juices analyzed at both the high and the low inoculum levels. Repeatability and reproducibility values were not significantly different either within juices, within trials, or across all samples tested in both trials. K agar is suitable for isolation of A. acidoterrestris spores from fruit juices.

Bacillus↗

PubMed2003

An inter- and intra-laboratory comparison of breath ¹³CO₂analysis.

BACKGROUND: ¹³C breath test analysis requires accurate ¹³CO₂measurements. AIM: To perform a multicentre study to evaluate the repeatability and reproducibility of breath ¹³CO₂analysis. METHODS: Two series of 25 paired randomly coded tubes (each consisting of 23 ¹³CO₂-enriched breath samples and two samples of standard reference pure CO₂with certified δ ¹³C(PDB)) were sent to participating centres for ¹³CO₂measurement. Each series of tubes was analysed 10 days apart. The repeatability and reproducibility of ¹³C measurements was assessed by Mandel's k and h statistics. RESULTS: Twenty-two centres participated in the study: 18 showed good inter- and intra-laboratory variability, whilst four showed abnormally high inter- or intra-laboratory variability. Breath test results were also significantly affected by the accuracy of the ¹³C analytical procedures. CONCLUSIONS: A low accuracy of ¹³C measurements may significantly affect the results of breath tests, leading to inappropriate clinical decisions. Standardization of ¹³C analysis is required to guarantee optimal ¹³C measurements and accurate ¹³C breath test results.

Breath Tests↗

PubMed2004

Development of a liquid chromatography-electrospray mass spectrometric method for the simultaneous analysis of benzoxazolinones and their degradation products.

A new method for the simultaneous analysis of some benzoxazolinones, aminophenoxazinones and malonamic acids was developed based on liquid chromatography (LC) coupled to mass spectrometry (MS), using electrospray ionization (ESI) and operating in positive mode. Different ESI-MS parameters, such as fragmentor voltage, capillary voltage, drying gas flow, nebulizer gas pressure and drying gas temperature, were optimized in order to obtain structural information and to achieve maximum sensitivity. Chromatographic separation was performed by a reversed-phase LC column using a linear gradient of water and methanol. Quality assurance of the developed method was assessed by measuring parameters as linearity, sensitivity, repeatability and reproducibility. Quantification method based on the use of internal standard was developed, selecting synthetic 2-methoxy-2H-1,4-benzoxazin-3(4H)-one as internal standard. Good correlations were obtained for all analytes relative to this compound in the range of 0.05-1.5 ng/microL. Instrumental detection limits were between 0.02 and 0.2 ng/microL. Repeatability and reproducibility studies showed acceptable coefficient of variation values.

Benzoxazoles↗

PubMed1997

Improved reproducibility of measurements with the nerve fiber analyzer.

PURPOSE: This study was undertaken to assess and improve the repeatability and reproducibility of nerve fiber layer (NFL) measurements using the Nerve Fiber Analyzer (NFA I), a scanning laser polarimeter. METHODS: The repeatability of two subsequent measurements was determined in 100 healthy eyes. Four methods of image evaluation were performed. Polarimetric measurements of retinal NFL were obtained along a peripapillary band at the superior and inferior poles of the optic disk and analyzed in a one-pixel band of absolute retardation values (method 1) and relative to the nasal segment (method 2). Method 3 used measurements obtained in a 10-pixel band along the same peripapillary band. Method 4 comprised measurements in selected areas outside the peripapillary band, which did not contain blood vessels. The repeatability (r) and relative reliability coefficient (Rel) were assessed as indices of agreement of repeated measurements. In addition, the reproducibility (R) from day to day for methods 3 and 4 was assessed by taking 10 images on 10 consecutive days from each of 10 subjects. RESULTS: The 95% critical value for r in the superior and inferior segments improved from about 30% for methods 1 and 2, to 23% for method 3, and to 11% for method 4. For the superior and inferior segments, the fourth method of image evaluation yielded a Rel of 98%, as compared with 54% in method 1, 80% in method 2, and 87% in method 3. The 95% critical value for R was 23% for method 3 but only 15% for method 4. CONCLUSIONS: The improved reproducibility of measurements has made the NFA I a promising device. An improved reproducibility (smaller limit for detecting change) does not necessarily indicate good sensitivity and specificity for any instrument. The role of the scanning laser polarimeter in clinical practice requires further study.

Humans↗

PubMed1986

Evaluation of an ISO draft proposal for sampling and analysis of chlorinated hydrocarbon solvent vapors in workplace atmospheres.

The ISO draft proposal for sampling and analysis of chlorinated hydrocarbon solvent vapors in workplace atmospheres (ISO/TC 146/SC 2/WG4 N41) has been evaluated by means of a round-robin test. For this purpose, the repeatability and reproducibility for the determination of tetrachloromethane, trichloromethane, 1,1,1-trichloroethane, trichloroethene were determined at three concentration levels. Furthermore, parameters such as breakthrough and loss on storage were determined. Samples were taken by 11 participants from six countries. After statistical evaluation of the results, it appeared that improvements were necessary for the determination of tetrachloromethane and trichloromethane. For the other three compounds, repeatability and reproducibility were sufficient. Possible error sources and possibilities for improvements are discussed.

Air Pollutants, Occupational↗

PubMed2000

A study of repeated measures of softest and loudest phonations.

One common way to describe one's voice in an objective way is to measure the sound levels of the softest (pianissimo) and loudest possible (fortissimo) phonations at given pitches (voice range profile measurement). However, the reliability of the measurement has not been thoroughly investigated. The aim of the present study was to describe the repeatability and reproducibility of the sound level measurement in statistical terms, focusing on five target frequencies within the estimated speaking pitch range. Ten healthy female university students volunteered as test subjects. The voice range profiles within the speaking pitch range were defined 10 times in succession and in five sample sessions between 45-minute-long oral readings. Our study followed the ideas of the Gage repeatability and reproducibility design. The results showed that the method used was reliable in fortissimo phonations at four of the measured frequencies. Better reliability can be achieved by measuring three successive phonations at each pitch prior to the next target tone.

Adult↗

PubMed2004

Joint IDF-IUPAC-IAEA(FAO) interlaboratory validation for determining aflatoxin M1 in milk by using immunoaffinity clean-up before thin-layer chromatography.

A collaborative study was conducted under the auspices of the International Dairy Federation (IDF), the International Union of Pure and Applied Chemistry (IUPAC) and the International Atomic Energy Agency (IAEA), a collaborative Food and Agricultural Organization (FAO) body fully to validate a method combining immunoaffinity clean-up to thin-layer chromatography for the determination of aflatoxin M(1) in milk. Work was done in order to afford those laboratories not equipped with high-performance liquid chromatography, mainly from developing countries, with a simplified but fully validated method as an alternative to the European validated immunoaffinity-high performance liquid chromatography method published as an EN ISO Standard 14501, February 1999. The validation study was carried out on samples of aflatoxin M(1)-contaminated milk and milk powder at levels close to the tolerable level of 0.5 microg l(-1) as recommended by the Codex Alimentarius and to the regulatory level of 0.05 microg l(-1) as laid down by the European Commission. Fourteen laboratories representing 11 countries participated in the trial. The relative standard deviations for repeatability and reproducibility based on raw data were in the range 27-48 and 35-54%, respectively. The recovery rate varied from 32 to 120%. The mishandling of two crucial steps of the protocol such as matrix sample reconstitution and extract evaporation could explain the wide variation of the recovery rate. For this reason, data were then corrected for recovery. Consequently, the relative standard deviations for repeatability and reproducibility were recalculated after correction for recovery and were in the range 26-54 and 34-53%, respectively. The method will be published as a standard ISO/DIS 14674--IDF 190.

Aflatoxin M1↗

PubMed2006

Reliability of a functional clinical test battery evaluating postural control, proprioception and trunk muscle activity.

OBJECTIVE: The purpose of this study was to examine the repeatability and reproducibility of the different tests of a clinical test battery evaluating the components of functional spinal stability: postural control (sway velocity data), proprioception (repositioning error), and muscle activation (electromyographic data). DESIGN: A total of 28 healthy volunteers participated in this study: 14 in the repeatability study and 14 in the reproducibility study. Each subject was tested three times, with an interval of 1 wk between the test sessions. The intraclass correlation coefficients and the standard error of the measurements as a percentage of the grand mean were calculated. RESULTS: The intraclass correlation coefficients for both the repeatability and the reproducibility evaluation showed good to excellent reliability for all variables (intraclass correlation coefficient, 0.60-0.98). The standard error of the measurements as a percentage of the grand mean ranged from 0.004 to 19.94. CONCLUSIONS: The functional clinical test battery investigated in this study proved to be a reliable tool in the assessment of healthy subjects. The evaluation of postural control, proprioception, and muscle activity (coordination, stabilization, maximal voluntary isometric contraction, endurance, and flexion-relaxation) showed good to excellent repeatability and reproducibility. Further analysis of the reliability of these variables in a clinical setting, particularly in patients with low back pain, seems appropriate.

Abdominal Muscles↗

PubMed1996

Accuracy of pedicle screw placement in lumbar vertebrae.

STUDY DESIGN: The location of pedicle screws (n = 42) in four human specimens of the lumbar spine and in 30 patients (n = 131 screws) after lumbar spinal fusion was assessed using computed tomography. OBJECTIVES: To determine the accuracy of pedicle screw placement in lumbar vertebrae and the reproducibility and repeatability of the computed tomography examination. SUMMARY OF BACKGROUND DATA: Failures in the placement of transpedicular screws for lumbar fusion are reported. The evaluation of such screws using computed tomography examination has not been investigated. METHODS: After surgery, the specimens were dissected in transversal slices to observe macroscopically the location of the pedicle screw and to correlate these observations with the computed tomography images. All patients were examined by one observer. To determine the reproducibility and repeatability of the computed tomography examination, two observers studied computed tomography images of 12 patients (n = 58 screws) twice within 3 months. RESULTS: In the specimens, 10 screws were observed to penetrate the medial wall of the pedicle. This correlated fully with the images. In the patients' group, 40% of all screws penetrated the cortex of the vertebra. Of all screws, 29% penetrated the medial wall of the pedicle. From the computed tomography images, it appeared that a deviation of more than 6 mm medially was a high risk for nerve root damage. Three months after his first examination, Observer 1 documented a different position in three of 58 screws (kappa = 0.90). Observer 2 found a different position in eight screws (kappa = 0.65). The comparison between the reviews of the two observers showed a different opinion for the first evaluation, four disagreements (2-4 mm) and 17 disagreements (0-2 mm; kappa = 0.34), and for the second evaluation, four disagreements (2-4 mm) and 12 disagreements (0-2 mm; kappa = 0.43). CONCLUSIONS: Correct placement of transpedicular screws for spinal fusion seems to be more difficult than it looks. The computed tomography scanning is useful for differential diagnosis of postoperative radicular syndromes after lumbar transpedicular fixation.

Bone Screws↗

PubMed1998

Characterization of bifidobacteria by random DNA amplification.

RAPD conditions were optimized to generate reproducible banding patterns by testing primers, thermocyclers and overall reproducibility in repeat DNA analysis and separate DNA extractions. Five primers were chosen on the basis of band intensity and distribution (between 2 and 10 bands) which clearly distinguished among strains of Bifidobacterium adolescentis, B. animalis, B. bifidum, B. breve, B. infantis and B. longum. The use of five single-primer reactions under optimized conditions improved the resolution and accuracy of the RAPD method for the characterization of dairy-related bifidobacteria. The results indicated that this method was highly reproducible in repeated analysis. Similarity between bifidobacteria strains was evaluated based on their RAPD profiles. Using a set of five primers, it was demonstrated that it may be possible to distinguish three different species of Bifidobacterium (B. breve, B. bifidum and B. adolescentis), based on similarity of the RAPD profiles to known reference strains. Furthermore, application of the RAPD technique may also be useful and faster, than traditional systematics for placement of industrial strains into specific clusters (either B. longum/infantis or B. animalis/lactis).

Animals↗

PubMed1998

Capillary sample introduction of polymerase chain reaction (PCR) products separated in ultrathin slab gels.

Polymerase chain reaction (PCR) amplified short tandem repeat (STR) samples from the HUMVWF locus have been analyzed using a unique sample introduction and separation technique. A single capillary is used to transfer samples onto an ultrathin slab gel (57 microm thin). This ultrathin nondenaturing polyacrylamide gel is used to separate the amplified fragments, and laser-induced fluorescence with ethidium bromide is used for detection. The feasibility of performing STR analysis using this system has been investigated by examining the reproducibility for repeated samples. Reproducibility is examined by comparing the migration of the 14 and 17 HUMVWF alleles on three consecutive separations on the ultrathin slab gel. Using one locus, separations match in migration time with the two alleles 42 s apart for each of the three consecutive separations. This technique shows potential to increase sample throughput in STR analysis techniques although separation resolution still needs to be improved.

Acrylamide↗

PubMedDate not supplied

Residue analysis of organophosphorus and organochlorine pesticides in fatty matrices by gas chromatography coupled with electron-capture detection.

A multiresidue method for the simultaneous determination of 22 organochlorine (OCs) and organophosphorus (Ops) pesticides (including isomers and metabolites), representing a wide range of physicochemical properties, was developed in fatty matrices extracted from meat. Pesticides were extracted from samples with acetonitrile/n-hexane (v:v, 1:1). The analytical screening was performed by gas chromatography coupled with electron-capture detection (ECD). The identification of compounds was based on their retention time and on comparison of the primary and secondary ions. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of samples fortified at 38 to 300 ng/g levels. Correlation coefficients for the 22 extracted pesticide standard curves (linear regression analysis, n = 3) ranged from 0.998 to 1.000. Recovery studies from 2 g samples fortified at 3 levels demonstrated that the GC-ECD method provides 64.4-96.0% recovery for all pesticides except 2,4'-DDE (44.6-50.4%), 4,4'-DDE (51.1-57.5%) and 2,4'-DDT (50.0-51.2%). Both repeatability and reproducibility relative standard deviation values were < 20% for all residues. Detection limits ranged from 0.31 to 1.27 ng/g and quantification limits were between 1.04 and 4.25 ng/g. The proposed analytical method may be used as a simple procedure in routine determinations of OCs and Ops in meat. It can also be applied to the determination of pesticide multi-residues in other animal products such as butter and milk.

Chromatography, Gas↗

PubMedDate not supplied

[Validation of triiodothyronine sodium analysis method].

OBJECTIVE: To validate the ultraviolet spectrophotometry analytical method for triiodothyronine sodium in order to use this method in the quality control process of a diluted powder of said active principle for the manufacturing of 25 mcg capsules. MATERIAL AND METHODS: An ultraviolet spectrophotometry analysis is performed on triiodothyronine sodium to obtain its spectrum. Subsequently, a mother solution of triiodothyronine sodium is made, from which 5 different-concentration dilutions are prepared in order to obtain a calibration line allowing the study of the method's linearity. Then 3 of these 5 dilutions are selected for repeatability and reproducibility studies. Two pattern solutions with differing concentrations are prepared for the accuracy study. Three different-concentration dilutions are prepared from each of them. The absorbencies of controls for both pattern solutions are measured to compare results obtained. RESULTS: A scan is performed between 350 and 200 nm, and an experimental peak of 319 nm is obtained. The method proves linear for the considered range of concentrations (r(2) = 0.9985). Variation coefficients are around 2%, thus indicating good repeatability and reproducibility. The mean percentage of recovery in known-concentration samples does not significantly differ from the theoretical 100%. CONCLUSION: The studied analytical method is adequately reliable to result in a foreseen result within defined intervals.

Capsules↗

PubMed1989

Clinical usefulness of ultrashort-lived iridium-191m from a carbon-based generator system for the evaluation of the left ventricular function.

Ultrashort-lived 191mIr (4.96 sec; 63-74 and 129 keV photons) is potentially advantageous for first-pass radionuclide angiocardiography, offering the opportunity to perform repeat studies with very low absorbed radiation dose to the patient. Left ventricular (LV) first-pass studies were performed in 72 patients with 191mIr from a new bedside 1.3 Ci (48.1 GBq) 191Os/191mIr generator system using an activated carbon support that offers high 191mIr yields (15-18%) and consistent low 191Os breakthrough (2-4 x 10(-4)%/bolus). Using a single crystal digital gamma camera, uncorrected end-diastolic counts in the left ventricular representative cycle ranged from 10 up to 30 k counts. The reproducibility of repeated LV ejection fraction (LVEF) determination at 2-min intervals in 50 patients was r = 0.97, mean diff. = 2.08 +/- 1.55 EF units. Comparison between 191mIr (80-120 mCi; 2,960-4,400 MBq) and 99mTc (20-25 mCi; 750-925 MBq) LV count rates indicates a 3 wk useful shelf life of this new generator system for cardiac studies. Iridium-191m determined LVEF correlated closely with 99mTc determined LVEF in 32 patients (r = 0.96, mean diff. = 1.87 +/- 1.23 EF units). Parametric images for LV wall motion analysis were comparable with both isotopes. We conclude that rapid, repeat, and reproducible high count rate first-pass left ventricular studies can be obtained with 191mIr from this new 191Os/191mIr generator system using a single crystal digital gamma camera.

Adult↗