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Results for “Repeatability and Reproducibility”

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PubMed2001

Interlaboratory reproducibility of standard accelerated aging methods for oxidation of UHMWPE.

During accelerating aging, experimental uncertainty may arise due to variability in the oxidation process, or due to limitations in the technique that is ultimately used to measure oxidation. The purpose of the present interlaboratory study was to quantify the repeatability and reproducibility of standard accelerated aging methods for ultra-high molecular weight polyethylene (UHMWPE). Sections (200 microm thick) were microtomed from the center of an extruded rod of GUR 4150 HP, gamma irradiated in air or nitrogen, and circulated to 12 institutions in the United States and Europe for characterization of oxidation before and after accelerated aging. Specimens were aged for 3 weeks at 80 degrees C in an air circulating oven or for 2 weeks at 70 degrees C in an oxygen bomb (maintained at 503 kPa (5 atm.) of O2) in accordance with the two standard protocols described in ASTM F 2003-00. FTIR spectra were collected from each specimen within 24 h of the start and finish of accelerated aging, and oxidation indices were calculated by normalizing the peak area of the carbonyl region by the reference peak areas at 1370 or 2022 cm(-1). The mean relative interlaboratory uncertainty of the oxidation data was 78.5% after oven aging and 129.1% after bomb aging. The oxidation index measurement technique was not found to be a significant factor in the reproducibility. Comparable relative intrainstitutional uncertainty was observed after oven aging and bomb aging. For both aging methods, institutions successfully discriminated between air-irradiated and control specimens. However, the large interinstitutional variation suggests that absolute performance standards for the oxidation index of UHMWPE after accelerated aging may not be practical at the present time.

Biocompatible Materials↗

PubMed2006

Chemical-thermal quantitative methodology for carbon speciation in damage layers on building surfaces.

The issue of environment protection, including the conservation of the monumental heritage worldwide, is related to atmospheric pollution, and its future therefore depends on air pollutant reduction. Carbonaceous particles emitted by combustion processes are the main factors responsible for the blackening of buildings. The identification and evaluation of the carbon species constituting the noncarbonate fraction of total carbon in damage layers, particularly in urban areas, are required in orderto investigate atmospheric deposition on building surfaces. Since noncarbonate carbon contains organic and elemental carbon originating from various human activities, its measurement and speciation are crucial to the protection and conservation of monuments and ancient masonry, playing an important role both in the proposal of mitigation strategies and in the definition of conservation treatments. The availability of a correct, accurate, and reproducible analytical method for a complete carbon balance is essential in studying the effects of atmospheric pollutants on the environment, including those affecting cultural heritage. A chemical-thermal methodology was set up, and its sensitivity, accuracy, repeatability, and reproducibility were tested on appropriate standard samples of composition similar to the black crusts on stones and mortars. The results indicate thatthe technique satisfactorily distinguishes among carbon species, particularly those of anthropogenic origin, allowing a reliable evaluation of their quantities in damage layers. In view of the difficulties encountered in applying the thermo-optical methods adopted for the measurement of carbon filters, the proposed methodology contributes to filling the current gap in suitable and reliable analytical procedures in the field of cultural heritage protection.

Air Pollution↗

PubMed2006

[Reproducibility of optic nerve head and retinal nerve fiber layer thickness measurements using optical coherence tomography].

PURPOSE: To evaluate the reproducibility of repeated quantitative measurements of optic nerve head topography and retinal nerve fiber layer thickness. METHODS: This study included 32 normal subjects, 41 patients with ocular hypertension and 33 patients with glaucoma. The study groups were defined by the intraocular pressure levels, optic disc stereo-photographs and perimetric performance. Optic disc and retinal nerve fiber layer assessments were performed by ocular coherence tomography (OCT III, Zeiss Instruments). OCT examination was repeated three times in each subject and the coefficient of variability was elaborated for each parameter and group of the study, and compared among them. RESULTS: The average retinal nerve fiber layer thickness measurement showed the best reproducibility figures with a coefficient of variability of 5.9%. The inferior quadrant and the 10, 6 and 7 clock-hours (coefficients of variability 6.3%, 7.4%, 7.5% and 8.6% respectively) showed higher reproducibility. The optic nerve head assessment showed the best reproducibility for the cup-to-disc ratios (vertical, horizontal and area ratios), with a coefficient of variability of 5.0%, 4.2% and 6.6% respectively. Although differences among groups were barely statistically significant, the glaucoma group showed coefficients of variability higher than the other two groups. CONCLUSIONS: Optic nerve head analysis and retinal nerve fiber layer thickness can be reproducibly assessed by OCT. The reproducibility of the device supports its potential use for ocular hypertension follow-up, although its use in glaucoma patients may present difficulties in some parameters.

Female↗

PubMed2000

Ultrasound assessment of atherosclerotic vessel wall changes: reproducibility of intima-media thickness measurements in carotid and femoral arteries.

RATIONALE AND OBJECTIVES: Ultrasonography is widely used in cardiovascular research to quantify early atherosclerotic vessel wall changes. In this article, we examined the short- and long-term reproducibility of this technique in the common carotid artery, carotid bifurcation, common femoral artery, and superficial femoral artery. Furthermore, we assessed the effect of progressed atherosclerosis on reproducibility. METHODS: Repeated ultrasound examinations were performed by one observer on 15 healthy individuals and 18 patients suffering from coronary heart disease. Intima-media thickness was determined by B-mode ultrasonography. The examinations were repeated by the same observer after a short time interval (short-term) and after a few weeks (long-term) and expressed as the mean difference between the measurements and the coefficient of variation (CV). RESULTS: The reproducibility of the intima-media thickness determination turned out to be best in the common carotid artery and the superficial femoral artery when performed in healthy controls (CV 5.6% and 5.5%, respectively). Reproducibility was less in patients with clinical atherosclerosis; this especially affected the reliability of the superficial femoral artery measurement (CV in healthy controls was 5.5%; in coronary heart disease patients, 17.5 %). The reliability of the intima-media thickness measurements in the common carotid artery (CV in healthy controls was 5.6%; in coronary heart disease patients, 9.5%) proved to be least affected by progressed atherosclerosis. A longer time interval between measurements did not affect the reproducibility of intima-media thickness measurements in healthy controls, whereas in the patients it led to some decrease of reproducibility and to a major decrease in reproducibility of the superficial femoral artery measurements (CV changed from 12.7% to 17.5%). CONCLUSIONS: Ultrasonography is a reliable and accurate technique to determine intima-media thickness in superficial arteries. In studies in which the intima-media thickness determination is used as a marker for generalized and coronary atherosclerosis, the common carotid artery should always be included, whereas the benefit of inclusion of other arteries depends on age and the expected extent of atherosclerosis in the individuals studied.

Adult↗

PubMed1989

Reproducibility of microscopic and cultural data in repeated subgingival plaque samples.

In association studies, micro-organisms can only be recognized as suspects for playing a major rôle in the development of a pathological environment, if their destructive action goes along with a marked proportional increase of their numbers or if their first detection can be related to the clinical onset of the disease. Limitations in the reproducibility of repeated samples have to be taken into account, when changes of the microbial composition of subgingival environments are to be studied, and when local clinical changes are to be related to shifts in the composition of the pertaining microbiological compartment. To study reproducibility, a total of 109 sites was sampled repeatedly with sterile paperpoints at an interval of 7 to 10 days in 24 patients suffering from periodontal disease and 12 edentulous patients wearing successful and failing osseointegrated titanium implants. Using continuous anaerobic techniques, the samples were cultured on nonselective and selective media and were studied by darkfield microscopy. Both the intertest-agreements of frequencies of detection (kappa-statistics) as well as the discrepancies of proportions of bacterial groups and selected bacterial species were determined. The standard deviation of proportional differences between first and second samples ranged between 6.4% (fusiform organisms) and 17.2% (coccoid cells) for darkfield parameters, between 4.3% (B. melaninogenicus on ETSA/Kana.) and 14.0% (B. gingivalis on ETSA/Kana.) for selected bacterial species and between 6.9% (gram-negative anaerobic cocci) and 24.0% (gram-positive facultative cocci) for bacterial groups classified according to gram stain characteristics and atmospheric growth conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗

PubMed1993

Left ventricular measurements with cine and spin-echo MR imaging: a study of reproducibility with variance component analysis.

The authors studied the reproducibility of repeated measurements of left ventricular volumes, weight, and wall stress as determined with cine and spin-echo magnetic resonance (MR) imaging. Two observers analyzed 40 serial MR imaging examinations twice, yielding a total of 160 repeated measurements. Estimates of 95% ranges for change were ejection fraction, 10% and 12%; wall mass, 16% and 21%; and wall stress, 22% and 20%, for measurements derived from cine MR imaging and spin-echo MR imaging, respectively. Reproducibility was not significantly different between cine and spin-echo MR imaging. Intraobserver, interobserver, and interexamination errors were quantitated with variance component analysis. Interexamination variability was the single most important contributor to total variance. Reproducibility of left ventricular chamber volume measurements with MR imaging is superior to that of other imaging modalities. In addition, MR imaging can provide reliable estimates of wall mass and wall stress. Efforts to improve reproducibility should be aimed at lowering interexamination variability.

Adult↗

PubMed2005

[Measurement of head penetration on digitalized radiographs: reproducibility and accuracy].

PURPOSE OF THE STUDY: Wear of the acetabular component of total hip arthroplasty (THA) is incriminated as the cause of loosening and bone resorption. Consequently, an accurate evaluation of wear can contribute to the prediction of mechanical failure of the arthroplasty. Among the different methods proposed, digitalized imaging using a high-resolution scanner associated with data processing procedures appears to be a simple easily accessible technique. A system based on this concept has been introduced in orthopedics. To our knowledge, there has been no report on the system's reproducibility and accuracy. MATERIAL AND METHODS: Thirty-nine radiography series for THA served as the basis for the evaluation of intra- and interobserver reproducibility. We evaluated the error induced by digitalization, the error induced by digitalized measurement, the accuracy of the measurements as a function of the material constituting the bearing, the intra- and interobserver reproducibility for repeated measures of THA wear (six observers and two observations). All measurements were done after digitalization and analyzed with a specimen designed software. RESULTS: The inter and intra-observer coefficients of concordance were 0.6 and 0.58 respectively, i.e. moderate reproducibility. Depending on the prosthetic material, the error and accuracy of the system varied from 0.112 to 0.44 mm and 0.28 to 1.29 mm respectively. To obtain valid inter-observer reproducibility, the number of observers had to be limited to three (coefficient = 0.82). The type of implant had an influence on measurement error. The error was 0.342 for polyethylene cups and 0.118 for press-fit metal back cups. Likewise, for a metallic head measuring 22.2 mm, the error was 0.138 mm while for a ceramic head or metal head measuring 28 mm, the error was 0.28 mm and 0.112 mm respectively. DISCUSSION AND CONCLUSION: The accuracy and error depend directly on the type of implant. The accuracy was better for metallic heads associated with metal-backed cups. To obtain satisfactory interclass correlation, the number of observers should be three. The proposed digitalized measurement system should be relatively accurate and reproducible. Its use can be recommended for the evaluation of wear after five years of follow-up, limiting the number of observers to three.

Acetabulum↗

PubMed2001

Clinical evaluation of the Shin-Nippon SRW-5000 autorefractor in children.

The Canon Autoref R-1 is an 'open-field' autorefractor which has been widely used for research purposes for the past 20 years, but is no longer manufactured. A new autorefractor, the Shin-Nippon SRW-5000, is now available, and if measures using this instrument are shown to be equally accurate and reliable, is likely to replace the R-1. Here we report on the accuracy and reliability (repeatability and reproducibility) of refraction measures in a paediatric population (from 4 to 8 years of age). Subject numbers were 44 for cycloplegic measures and 53 for non-cycloplegic measures. As would be expected, agreement with cycloplegic refraction and reliability were better when SRW-5000 measures were taken using cycloplegia. Repeatability results from the SRW-5000 autorefractor, both with and without cycloplegia were similar to those reported for the Canon R-1.

Accommodation, Ocular↗

PubMed2005

Reproducibility of black-blood coronary vessel wall MR imaging.

PURPOSE: New magnetic resonance imaging (MRI) methods can provide high spatial resolution images of the coronary artery wall, and statistically significant differences in coronary vessel wall thickness between atherosclerotic disease patients and control subjects have been shown. The aim of this study is to assess inter-study reproducibility (i.e., repeatability) of the cross-sectional 2D coronary vessel wall MRI using a black-blood technique. METHODS AND RESULTS: Twelve healthy adult subjects were studied with the use of a commercial 1.5 T CMR system. A double inversion recovery fast spin-echo (FSE) sequence (black blood) was used. Each subject was scanned twice on different days. The mean RCA lumen area difference between study 1 and study 2 was 0.004 mm2, and the coefficient of repeatability (COR) was +/- 0.06 mm2. The mean RCA wall thickness difference between study 1 and study 2 was 0.02 mm, and the COR was +/-0.39 mm. CONCLUSION: Cross-sectional coronary vessel wall imaging with 2D double-IR FSE is highly reproducible for serial evaluation of coronary vessel walls and atherosclerotic coronary artery disease.

Adult↗

PubMedDate not supplied

European intercomparison study for the determination of the fumonisins content in two maize materials.

The results of an intercomparison study for the analysis of fumonisin B1 (FB1) and fumonisin B2 (FB2) in a contaminated maize material (Maize B, containing approximately 2 micrograms/g FB1 and 1 micrograms/g FB2) and its 'blank' counterpart (Maize A, containing less than 20 ng/g FB1 and FB2) are reported. Maize materials were distributed in 60 g sachets, submitted to gamma-irradiation at 15 kGy, and distributed to participating laboratories. The study was carried out by 24 European laboratories, most of which have national or international responsibilities for food/feed quality control. Participants used basically one method with some modifications, based on clean-up through SAX minicolumn and reversed phase HPLC with fluorescence detection of the OPA-fumonisin derivatives. The intercomparison study generated data (after correction for recoveries) with repeatability and reproducibility levels of: RSDr = 10% and RSDR = 11% for FB1; RSDr = 11% and RDSR = 13% for FB2. The recoveries obtained by most participants were considered low (70% for FB1 and 69% for FB2), being considerably affected by the extraction mode. Average recoveries for laboratories using blending were 62% and 60%, whereas for laboratories using shaking they were 85% and 86% for FB1 and FB2, respectively. The day-to-day- data showed a between-day, within-laboratory repeatability lower than 15% (CV < 15%) for FB1 for all laboratories, whereas only three laboratories obtained a between-day, within-laboratory reproducibility higher than 15% (CV > 15%) for FB2.

Animal Feed↗

PubMed2002

Heart rate: an important confounder of pulse wave velocity assessment.

Arterial stiffness is a strong determinant of cardiovascular risk. Pulse wave velocity (PWV) is an index of arterial stiffness, and its prognostic value has been repeatedly emphasized. The purpose of the present study was to assess the effect of heart rate (HR) on PWV. Twenty-two subjects with a mean age of 77.8+/-8.4 (SD) years and permanent cardiac pacing were studied. In each subject, PWV was measured at 5 different pacing frequencies in the same session (60, 70, 80, 90, 100 bpm), the order of the various frequencies being randomly determined. Furthermore, to test the reproducibility, a repeat measurement of PWV was obtained in one randomly selected frequency. Blood pressure (BP) was measured by conventional means at each pacing frequency. PWV appeared fairly reproducible because no significant difference was disclosed between the 2 measurements obtained at the same HR level (P=0.5) and both measurements were strongly correlated (r=0.87, P<0.001). No significant BP variation was observed during pacing. There was a highly significant effect of HR on PWV estimated by a one-way, within-subjects analysis of variance (P=0.01). This study demonstrates that HR is an important factor in the intraindividual variation of PWV in elderly subjects. This raises methodological concern about the measurement of this parameter. Standardizing PWV for HR level seems mandatory if one wants to interpret PWV changes in clinical trials or in the follow-up of patients.

Aged↗

PubMed2002

Accuracy and repeatability of prostate volume measurements by transrectal ultrasound.

We evaluated six alternative methods of prostate volume determination by transrectal ultrasound, three based on planimetry and three based on measurement of prostate diameters. Prostate volume measurements were made on an average of 6.5 occasions over a 3 y period on 41 patients with benign prostatic hyperplasia, using standard techniques. We defined the average of multiple planimetries as the prostate reference volume. Agreement with the reference volume and reproducibility at repeat testing was in the same range for single planimetry and volume determinations based on the formulas height (H) x width (W) x length (L) x pi/6 and W x W x H x pi/6, but was poorer using the formula W x W x W x pi/6. Using the average result of two successive planimetry measurements increased the reproducibility of planimetry, being statistically significantly better than for one single planimetry (P=0.024) or for the formula W x W x H x pi/6 (P=0.048). Our study suggests that the simple formula based methods of prostate volume determination provide results that are only marginally inferior to one single planimetry, but results are improved by performing two planimetry measurements.

Aged↗

PubMed2005

Determination of ochratoxin A in wine by liquid chromatography tandem mass spectrometry after combined anion-exchange/reversed-phase clean-up.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus and Penicillium verrucosum. It has been found and analysed in several foods and feeds. Owing to its toxicity and occurrence in food and feed, the European Community has issued directives and some countries have their own regulations for OTA contents in food, feed and beverages. This work describes a method for the determination of OTA in mulled and red wine. It is based on combined anion exchange/reversed-phase clean-up and was analysed by liquid chromatography coupled with tandem mass spectrometry (multiple reaction monitoring). The method was validated with natural contaminated and spiked wine samples with OTA contents from 1.34 to 3.48 microg kg(-1). Owing to its accuracy, good reproducibility and repeatability, this easy method is a good alternative to liquid chromatography-fluorescence detection methods.

Chromatography, Liquid↗

PubMed1985

Assessment of transdiaphragmatic pressure in humans.

Maximal force developed by the diaphragm at functional residual capacity is a useful index to establish muscle weakness; however, great disparity in its reproducibility can be observed among reports in the literature. We evaluated five maneuvers to measure maximal transdiaphragmatic pressure (Pdimax) in order to establish best reproducibility and value. Thirty-five naïve subjects, including 10 normal subjects (group 1), 12 patients with chronic obstructive pulmonary disease (group 2), and 13 patients with restrictive pulmonary disease (group 3), were studied. Each subject performed five separate maneuvers in random order that were repeated until reproducible values were obtained. The maneuvers were Mueller with (A) and without mouthpiece (B), abdominal expulsive effort with open glottis (C), two-step (maneuver C combined with Mueller effort) (D), and feedback [two-step with visual feedback of pleural (Ppl) and abdominal (Pab) pressure] (E). The greatest reproducible Pdimax values were obtained with maneuver E (P less than 0.01) (group 1: 180 +/- 14 cmH2O). The second best maneuvers were A, B, and D (group 1: 154 +/- 25 cmH2O). Maneuver C produced the lowest values. For all maneuvers, group 1 produced higher values than groups 2 and 3 (P less than 0.001), which were similar. The Ppl to Pdi ratio was 0.6 in maneuvers A and B, 0.4 in D and E, and 0.2 in C. We conclude that visual feedback of Ppl and Pab helped the subjects to elicit maximal diaphragmatic effort in a reproducible fashion. It is likely that the great variability of values in Pdimax previously reported are the result of inadequate techniques.

Abdominal Muscles↗

PubMed2006

Stability of IGF-I concentration despite divergent results of repeated GH stimulating tests indicates poor reproducibility of test results.

OBJECTIVE: Growth hormone (GH) secretion is routinely assessed in provocative tests. However, some limitations of these tests have been reported, including a weak correlation between spontaneous GH secretion and GH peak in stimulating tests, poor reproducibility of test results and normalisation of previously decreased GH response to stimulation in the repeated provocative tests. The observed discrepancies between the results of consecutive GH stimulating tests in the same patient may be explained either by real changes in GH secretion or by the poor reproducibility of GH response to stimulation. Normalisation of previously decreased GH secretion should entail the increase of insulin-like growth factor-I (IGF-I) concentration, while stability of IGF-I secretion despite divergent GH response to stimulation in repeated tests might indicate the poor reproducibility of GH stimulating tests. continue with The aim of the study was a comparison of GH peak in repeated stimulating tests and of corresponding, simultaneously measured IGF-I concentration. METHODS: The investigation comprised 84 children with short stature who underwent repeated GH tests and IGF-I evaluation. In 60 patients each of two different tests (with clonidine and with glucagon, in standard doses) was performed twice, together with IGF-I measurement during both evaluations. In 20 patients (remaining in the same pubertal stage during the time period between the procedures in question) at least one test, together with IGF-I measurement, was repeated within one year. RESULTS: The correlation between the results of GH tests, repeated during the two evaluations, was weak (r=0.22, p<0.05 for all patients and r=0.25, p<0.05 for the patients examined 2 times within 1 year), with the high within-subject variability (43.4 % and 59.5 %, respectively). Conversely, the correlation between two values of IGF-I SDS was good both for all patients (r=0.65, p<0.05) and especially for the patients examined twice within 1 year (r=0.96, p<0.05), with low within-subject variability for the latter subgroup of patients (11.2 %). The same GH stimulating tests, performed twice in the same patient, led to different conclusions (either the confirmation of GHD diagnosis or its exclusion) in most of examined patients. Poor reproducibility of GH stimulating tests, rather than the possibility of short-term changes in GH secretion, was confirmed.

Adolescent↗

PubMed1997

Cephalometric landmarks identification and reproducibility: a meta analysis.

To assess the magnitude of cephalometric landmarks identification error, we performed a Meta analysis on six pertinent studies. We outline the procedures used to compare and integrate the findings of these-studies. The results are a measure of systematic and random errors involved when locating landmarks on lateral head films. They are presented as standard mean errors and 95% confidence intervals for the repeatability and reproducibility of 15 cephalometric landmarks commonly used in growth analysis.

Cephalometry↗

PubMed1993

Radiological progression in rheumatoid arthritis: how many patients are required in a treatment trial to test disease modification?

OBJECTIVE: To determine whether the number of patients required in a therapeutic trial that uses progression of radiological abnormalities as the outcome measure would be similar for multiple centres. METHODS: The progression of radiological damage to the fingers and wrists of patients with rheumatoid arthritis in five centres, three in North America and two in Europe, was examined. The reproducibility of repeated readings by the same and multiple observers was examined. The number of patients required in a two group trial was calculated for several combinations of power and significance. RESULTS: Scoring progression of radiological abnormalities in sequential films taken between 0.5 and 2.1 years was found to be highly reproducible. When the scores of a single reader were used the rate of change of radiological scores was similar in all centres. Based on the mean progression rate for all centres it was estimated that 153 patients in each group would be required to assure 90% power for detecting a 50% slowing of radiological progression at a significance of 0.05. Review of the experience in three trials showed a large variability in the radiological progression rates. CONCLUSION: The progression of scores for radiological damage in rheumatoid arthritis is relatively uniform in North America and Europe and thus the number of patients required in a trial would be similar. Experience in three trials showed that patient selection is of paramount importance in setting up a successful study.

Adult↗

PubMedDate not supplied

Determination of crude protein in animal feed, forage, grain, and oilseeds by using block digestion with a copper catalyst and steam distillation into boric acid: collaborative study.

A collaborative study was conducted to evaluate the repeatability and reproducibility of an extension of AOAC Official Method 991.20, Nitrogen (Crude) in Milk, to animal feed, forage (plant tissue), grain, and oilseed materials. Test portions are digested in an aluminum block at 420 degrees C in sulfuric acid with potassium sulfate and a copper catalyst. Digests are cooled and diluted, and concentrated sodium hydroxide is added to neutralize the acid and make the digest basic; the liberated ammonia is distilled by using steam distillation. The liberated ammonia is trapped in a weak boric acid solution and titrated with a stronger standardized acid, hydrochloric acid; colorimetric endpoint detection is used. Fourteen blind samples were sent to 13 collaborators in the United States, Denmark, Sweden, Germany, and the United Kingdom. Recoveries of nitrogen from lysine, tryptophan, and acetanilide were 86.8, 98.8, and 100.1%, respectively. The within-laboratory relative standard deviation (RSDr, repeatability) ranged from 0.40 to 2.38% for crude protein. The among-laboratories (including within-) relative standard deviation (RSD(R), reproducibility) ranged from 0.44 to 2.38%. It is recommended that the method be adopted First Action by AOAC INTERNATIONAL. A lower concentration (1% H3BO3) of trapping solution was compared with the concentration specified in the original protocol (4% H3BO3) and was found comparable for use in an automatic titration system in which titration begins automatically as soon as distillation starts. The Study Directors recommend that 1% H3BO3 as an optional alternative to 4% boric acid trapping solution be allowed for automatic titrators that titrate throughout the distillation.

Animal Feed↗