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Results for “Reproducibility”

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PubMed1999

Validity and reproducibility of a food frequency interview in a Multi-Cultural Epidemiology Study.

PURPOSE: There is limited support for the validity and reproducibility of dietary assessment in culturally diverse populations. The goal of this study was to evaluate the comparative validity and reproducibility of a Food Frequency Questionnaire (FFQ) used in the observational, multi-cultural Insulin Resistance Atherosclerosis Study (IRAS). METHODS: Women (n = 186) were approximately equally distributed by ethnicity from one urban center (African Americans and non-Hispanic whites) and one rural center (Hispanics and non-Hispanic whites). The IRAS FFQ was modified from the National Cancer Institute Health Habits and History Questionnaire to include ethnic and regional foods. Validity was assessed by comparing dietary values, including supplements, obtained from the FFQ to the average intake estimated from a series of 8 24-hour dietary recalls collected by telephone over the same 1-year period. Reproducibility was assessed among women who reported no change in their usual diet (n = 133) by comparing data from the original IRAS FFQ (in-person) with the FFQ administered for the validity study (two to four years later, by telephone). RESULTS: Correlation coefficients for validity were statistically significant for most nutrients (mean r = 0.62 urban non-Hispanic white, 0.61 rural non-Hispanic whites, 0.50 African American, 0.41 Hispanic) and did not differ among subgroups of obesity or diabetes status. The median correlation coefficient for the total sample was 0.49. Correlations were lower for women with less than 12 years of education (mean r = 0.30; median r = 0.25). The lower correlations among Hispanics was largely explained by the lower educational attainment in that sample. For reproducibility, the mean correlation for nutrients evaluated was r = 0.62 (median r = 0.63) and did not differ for subgroups. CONCLUSIONS: Although educational attainment must be considered, the IRAS FFQ appears to be reasonably valid and reliable in a diverse cohort.

Adult↗

PubMedDate not supplied

Experimental verification of technetium 99m-labeled teboroxime kinetic parameters in the myocardium with dynamic single-photon emission computed tomography: reproducibility, correlation to flow, and susceptibility to extravascular contamination.

BACKGROUND: This research was undertaken to investigate the ability of dynamic single-photon emission computed tomographic (SPECT) imaging to quantify myocardial perfusion in vivo with 99mTc-labeled teboroxime. The objectives of this experiment were (1) to determine the reproducibility of the model parameters fv, K1, and k2 (volume fraction of blood in the tissue and wash-in and wash-out of 99mTc-labeled teboroxime in the myocardium, respectively), (2) to determine if the kinetics of 99mTc-labeled teboroxime correlate with an independent measure of myocardial blood perfusion, and (3) to determine the amount of extravascular activity in the arterial blood time-activity curve generated from the dynamic SPECT images. METHODS AND RESULTS: Twenty-nine studies were performed on 10 dogs. The dogs were divided into three groups: reproducibility, occlusion, and vasodilation. In the reproducibility protocol, the physiology was kept as constant as possible. In the occlusion and vasodilation protocols, myocardial perfusion was either decreased by occluding the left anterior descending coronary artery or increased by continuous adenosine infusion, respectively. In all studies an independent measure of myocardial perfusion was obtained with either radiolabeled microspheres or a flow probe, and the activity of 99mTc-labeled teboroxime in the arterial blood was monitored continuously. The root-mean-square errors calculated with data from the reproducibility group were 19.9% +/- 8.5%, 14.0% +/- 5.7%, and 14.5% +/- 5.0% for fv, K1, and k2, respectively. The occlusion group data showed that K1 demonstrated a higher correlation (r = 0.887) with microsphere myocardial perfusion than did k2 (r = 0.689). The results from the vasodilation group showed that K1 demonstrated a stronger relationship to myocardial blood flow (MBF) measured with a flow probe (K1 = 0.237 + 0.629 MBF [r = 0.935] and k2 = 0.177 + 0.263 MBF [r = 0.904]). Finally, the amount of extravascular activity in the blood time-activity curve generated from the dynamic SPECT images was determined to be 45.5% +/- 16.4%. CONCLUSIONS: The wash-in parameter K1 correlates with myocardial perfusion in dogs; therefore dynamic SPECT imaging of 99mTc-labeled teboroxime has the potential for measuring regional myocardial perfusion in patients.

Adenosine↗

PubMed2002

Reproducibility of electron-beam CT measures of aortic valve calcification.

RATIONALE AND OBJECTIVES: The authors performed this study to establish the interscan, interobserver, and intraobserver reproducibility of aortic valve calcification (AVC) measurements obtained with electron-beam computed tomography (CT). MATERIALS AND METHODS: The authors evaluated electron-beam CT scans from all patients who had undergone two serial examinations on the same day as part of a study of coronary artery calcification reproducibility. In patients in whom aortic valve calcium was identified at electron-beam CT, AVC scores were measured with both the Agatston and the volumetric methods, which were developed previously to quantify coronary calcium. RESULTS: Forty-four asymptomatic patients (mean age, 66 years +/- 9) with AVC at electron-beam CT were included in the analyses. AVC score reproducibility was excellent with both the Agatston and the volumetric methods (R2 = 0.99, P = .0001 for both), with median interscan variabilities of 7% and 6.2%, respectively. Interscan reproducibility was similar, whether the analysis included all scans or was restricted to those with scores greater than 10 or greater than 30. For the volumetric method, the median interobserver variability was 5% and the median intraobserver variability was 1%. CONCLUSION: The low interscan, interobserver, and intraobserver variabilities at electron-beam CT suggest that this method should be useful for the noninvasive monitoring of AVC changes over time and for assessing the efficacy of therapies aimed at slowing AVC accumulation.

Aged↗

PubMed2004

Reproducibility of a locomotor test for trotter horses.

Locomotion analysis is increasingly used to assess the gait of horses in the selection and training of equine athletes. We have developed a specific locomotor test for fast trotting harnessed horses that uses an accelerometric device. We describe here the reproducibility of the locomotor test and the validation of its use to analyse trotters on the racetrack. We measured the performance of eight horses under the same conditions three times in a single week. We then tested the influence of five tracks on the variables measured using eight different trotters every two days. The horses trotted at three or four velocities (8.3, 10, 11.7 m/s and at maximal velocity) in a straight line for 20 s. The short-term reproducibility of the test was very good for 23/25 variables, with no significant difference in the 23 variables for the three measurements. The two less reproducible variables reflected human error. The different tracks did not alter the stride variables measured. We conclude that the test is an easy, accurate method for analysing gait, as it provides reproducible stride variables for trotting harness horse under field conditions.

Animals↗

PubMed2000

Measurement of isometric muscle strength: a reproducibility study of maximal voluntary contraction in normal subjects and amyotrophic lateral sclerosis patients.

Amyotrophic lateral sclerosis (ALS) is a degenerative disease of unknown cause, resulting in the progressive loss of voluntary motor activity. Traditional methods of evaluating patients with ALS (neurologic assessment, manual muscle testing and rating scales) involve subjective elements and lack the sensitivity needed to detect small but meaningful changes in deterioration and therapeutic efficacy. This paper presents a recently developed strength measurement instrument, useful for the long-term monitoring of muscle strength deterioration in ALS. In addition, a reproducibility study to assess the intra- and interobserver reliability of maximal voluntary isometric contraction is reported. The strength measurement instrument consists of a strain gauge force transducer, a bridge amplifier and a mechanical structure to counteract movements. A personal computer acquires the strength signal during each voluntary contraction and automatically computes the maximal value. Reproducibility of measurement was assessed in 18 normal subjects tested twice, on successive days, with the same examiner and under the same conditions. The interexaminer reproducibility of measurement was assessed in a group of 13 normal subjects and 10 ALS patients. Each subject of the two groups was independently examined by three examiners. The two reproducibility studies showed a high intraclass correlation coefficient (0.91-0.97) and low SEM and measurement error (3-10%) in all muscle regions tested. The Bland and Altman plots confirmed these results.

Adult↗

PubMed2005

Reliability and reproducibility of gene expression measurements using amplified RNA from laser-microdissected primary breast tissue with oligonucleotide arrays.

Combined use of microdissection and high-density oligonucleotide arrays is a powerful technique to study in vivo gene expression. Because microdissection generally yields ng quantities of RNA, RNA amplification is necessary but affects array results. We tested the reliability and reproducibility of oligonucleotide array data obtained from small sample amplified RNA isolated from primary tissues via laser capture microdissection, to determine whether gene expression measurements obtained under these now customary conditions are reliable and reproducible enough to detect authentic expression differences between clinical samples. We performed eight U133A Affymetrix GeneChip oligonucleotide array hybridizations using RNA isolated from a single normal human breast specimen: two standard and six small samples prepared using independent microdissections, RNA isolations, and amplifications. We then performed six array hybridizations using RNA obtained similarly from paired normal epithelium and ductal carcinoma in situ from three independent breast specimens. We determined reliability by analysis of hybridization quality metrics, and reproducibility by analysis of the number of more than twofold changed genes, linear regression, and principal components analysis. All amplified RNA generated good quality hybridizations. From the initial specimen, correlations between replicates (r = 0.96 to 0.99) and between small samples (r = 0.94 to 0.98) were high, and between standard and small samples (r = 0.84) were moderate. In contrast, in the three normal cancer pairs, the differences in gene expression were large among the normal samples, the ductal carcinoma in situ samples, and between normal and ductal carcinoma in situ within each pair. These differences were a much larger source of variability than the technical variability introduced by the processes of laser capture microdissection, small sample amplification, and array hybridization. Nanogram quantities of RNA isolated from primary tissue using laser-capture microdissection generates reliable and reproducible gene expression measurements. These measurements do not mirror those obtained using micrograms of RNA. Biological variability in gene expression between independent specimens, and between histologically distinct samples within a specimen, is greater than the technical variability associated with the procedures. Future studies of in vivo gene expression using this approach will identify functionally important differences within or between specimens.

Breast Neoplasms↗

PubMed2002

Reproducibility of the heart rate response to low-strain Valsalva manoeuvre in healthy subjects.

To elucidate whether the intrastrain cardio-acceleration and cardio-deceleration responses to low-strain Valsalva manoeuvre at expiratory pressures 10 and 20 mmHg (VM10,VM20) are reproducible, a beat-to-beat heart rate study was undertaken in 46 subjects (40 male undergraduates aged 19-25 years and six laboratory workers (four females and two males aged 28-55 years). The intensity of the heart rate response (HRR) was assessed by a ratio of the mean value of the pre-strain heart rate (Valsalva means' ratio VMR). In each subject the HRR to VM10 and VM20 was measured by repeating each manoeuvre three times. Reproducibility was evaluated on a short-term (1 h), medium-term (1 and 6 months), and long-term (6 and 11 years) basis. With the individual differences the initial short-term reproducibility study revealed either an cardio-acceleration or cardio-deceleration response to VM10 and VM20, which persisted well in the repeated tests. On the ground of this result three individual modes of HRRs to VM10 and VM20 were distinguished: (i) Mode A, a deceleration response appeared both to VM10 and VM20; (ii) Mode B, a deceleration response appeared to VM10 and an acceleration response to VM20; (iii) Mode C, an acceleration response appeared both to VM10 and VM 20. All of these modes, as well as the separate acceleration and deceleration responses, were well reproducible at any cited time points. We suggest that the individual modes of HRR are induced by different states of autonomic cardiovascular reactivity: Mode A probably expresses a parasympathotonic (vagotonic), Mode C--a sympathotonic, and Mode B--an intermediate autonomic state. Thus, the individual modes of HRR to VM10 and to VM20 could be used as a method of non-invasive determination of cardiovascular autonomic reactivity.

Adult↗

PubMed2006

[Study on factors affecting reproducibility of migration time in capillary electrophoresis].

The effects of running buffer on reproducibility of the migration time in the modes of capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) were investigated. The parameters include concentration, pH value and the properties change of the running buffer. The results showed that the reproducibility of migration times may be improved through three approaches. First, the correlation between running buffer concentration and migration time was established and the running buffer concentration was determined by conductivities in order to improve the reproducibility. Second, it was found that the residual running buffer in the capillary showed significant influence on the repeatability of migration times. Thus, appropriate running or washing procedure between separations is necessary. Finally, the inlet reservior buffer plays an extremely important role in affecting the migration behaviors of solutes. Through improving the test apparatus, reproducible migration time was achieved as a result of increasing the frequency of replacing the buffer in the inlet reservior.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed1997

NIST/NCI Micronutrients Measurement Quality Assurance Program: measurement repeatabilities and reproducibilities for fat-soluble vitamin-related compounds in human sera.

The NIST/NCI Micronutrient Measurement Quality Assurance Program has conducted 33 interlaboratory comparison exercises for fat-soluble vitamin-related compounds in human sera over the past 12 years. Periodic reanalysis of lyophilized serum samples prepared from more than 70 different sera has enabled estimation of the short- and long-term measurement characteristics. Median- and interquartile-range-based statistics adequately estimate the distribution of results from laboratories that are in analytical control from total distributions that include a significant minority of outlier data. Short-term interlaboratory reproducibility standard deviations (SDs) are predictable functions of analyte concentration, with an asymptotic limit at low analyte concentration and a linear relationship at high concentrations. Long-term trends in the interlaboratory reproducibility can be estimated by standardizing the short-term SD at the observed analyte concentration to an expected SD at a given physiologically significant analyte concentration. The "average" laboratory's same-day analytical repeatability SD is about one-third of the estimated interlaboratory reproducibility; repeatability for longer periods between analyses is, on average, on better than the reproducibility. While a few exceptional laboratories have maintained excellent repeatability over the entire decade, long-term study measurements generated within a single laboratory are not generally more internally consistent than results from multiple laboratories. Enhanced and more consistently implemented intralaboratory quality control and quality assurance methods are required to further improve and maintain interlaboratory measurement comparability.

Humans↗

PubMed2006

Label-free protein quantification using LC-coupled ion trap or FT mass spectrometry: Reproducibility, linearity, and application with complex proteomes.

A critical step in protein biomarker discovery is the ability to contrast proteomes, a process referred generally as quantitative proteomics. While stable-isotope labeling (e.g., ICAT, 18O- or 15N-labeling, or AQUA) remains the core technology used in mass spectrometry-based proteomic quantification, increasing efforts have been directed to the label-free approach that relies on direct comparison of peptide peak areas between LC-MS runs. This latter approach is attractive to investigators for its simplicity as well as cost effectiveness. In the present study, the reproducibility and linearity of using a label-free approach to highly complex proteomes were evaluated. Various amounts of proteins from different proteomes were subjected to repeated LC-MS analyses using an ion trap or Fourier transform mass spectrometer. Highly reproducible data were obtained between replicated runs, as evidenced by nearly ideal Pearson's correlation coefficients (for ion's peak areas or retention time) and average peak area ratios. In general, more than 50% and nearly 90% of the peptide ion ratios deviated less than 10% and 20%, respectively, from the average in duplicate runs. In addition, the multiplicity ratios of the amounts of proteins used correlated nicely with the observed averaged ratios of peak areas calculated from detected peptides. Furthermore, the removal of abundant proteins from the samples led to an improvement in reproducibility and linearity. A computer program has been written to automate the processing of data sets from experiments with groups of multiple samples for statistical analysis. Algorithms for outlier-resistant mean estimation and for adjusting statistical significance threshold in multiplicity of testing were incorporated to minimize the rate of false positives. The program was applied to quantify changes in proteomes of parental and p53-deficient HCT-116 human cells and found to yield reproducible results. Overall, this study demonstrates an alternative approach that allows global quantification of differentially expressed proteins in complex proteomes. The utility of this method to biomarker discovery is likely to synergize with future improvements in the detecting sensitivity of mass spectrometers.

Amino Acid Sequence↗

PubMed2002

Reproducibility of the ventricular synchronization parameters assessed by multiharmonic phase analysis of radionuclide angiography in the normal heart.

Radionuclide angiography (RNA) permits analysis of contractility and conduction abnormalities. We determined the parameters of normal ventricular synchronization, assessed the reproducibility of the technique, and compared first harmonic (1H) and third harmonic (3H) analysis. Forty-four normal subjects (28 men and 16 women) were studied. RNA was performed in left anterior oblique (LAO) and left lateral (LL) projections. The onset (To), mean time (Tm), total contraction time (Tt) for right ventricle (RV) and left ventricle (LV), interventricular time (T(RV-LV) = Tm(LV - Tm(RV)) in LAO, and the apex-to-base time (T(a-b)) in LL were measured on the histograms of the time-activity curve. Reproducibility (R) was tested by studying 26 consecutive patients with two successive RNAs. RV starts contracting 25 ms before LV (To(RV) = 29 +/- 37 ms; To(LV) = 54 +/- 39 ms; mean +/- SD) with a 37 ms longer total contraction time. T(RV-LV) is 3 +/- 16 ms. In LL projection, apex and base contract synchronously: T(a-b) = 2 +/- 16 ms. 3H analysis enlarges all duration parameters (To, Tm and Tt), but does not alter synchronization (deltaT(a-b) and deltaT(RV-LV) between 1H and 3H <1%, p = NS). Reproducibility of the duration (T(tLV) and T(tRv)) and synchronization parameters (T(a-b) and T(RV-LV)) is high (R < or = 2.2%). In conclusion, the simultaneous contraction of right and left ventricles and of apex and base can be quantified by RNA phase analysis with high reproducibility. These results, consistent with published electrophysiological data, provide the basis for further non-invasive investigations of ventricular resynchronization in patients with basal electrical or mechanical asynchrony.

Female↗

PubMed2001

Choice of methodology for assessing genetic impacts of environmental stressors: polymorphism and reproducibility of RAPD and AFLP fingerprints.

PCR-based multi-locus DNA fingerprints represent one of the most informative and cost-effective measures of genetic diversity and are useful population-level biomarkers of toxicologic and other anthropogenic impacts. However, concerns about reproducibility of DNA fingerprints have limited their wider use in environmental biology. We assessed polymorphism and reproducibility of two common fingerprinting techniques, RAPD (randomly amplified polymorphic DNA) and AFLP (amplified fragment length polymorphism), in pedigreed populations of rainbow trout (Oncorhynchus mykiss) to derive general rules for selective removal of problematic fingerprint bands. We found that by excluding bands that comprised less than 1% of total intensity, and by excluding the largest and smallest 10% of the bands, we could achieve nearly 100% reproducibility of AFLP fingerprints. Similar application of band exclusion criteria to RAPD fingerprints did not significantly enhance their reproducibility, and at least 15% of RAPD bands were not fully repeatable, heritable, or transmittable. The RAPD technique produced more polymorphic fingerprints than AFLP; however, considering that a substantial proportion of RAPD markers did not demonstrate Mendelian inheritance patterns, the AFLP methodology is to be preferred for future research.

Animals↗

PubMed2003

Low reproducibility of 2 x 24-hour continuous esophageal pH monitoring in infants and children: a limiting factor for interventional studies.

The aim of this study was to investigate the day-to-day reproducibility of 24-hr esophageal pH monitoring. The procedure was performed continuously for 48 hr in order to enable future studies on dietary challenges, using consecutive 2 x 24 hr pH recording. Furthermore, one objective was to relate the degree of reproducibility to endoscopic evidence of mucosal injury. Upper endoscopy and 2 x 24-hr consecutive pH monitoring were performed in 30 infants and children referred for gastroesophageal reflux disease. The monitoring was performed without dietary or activity restrictions in order to assess reflux parameters in a near-normal physiologic setting. The NASPGHAN criteria for pathological reflux index (RI, % fraction of time with pH < 4.0) were employed. Based upon the NASPGHAN criteria for the RI, 9/30 subjects (30%) had discordant (normal vs pathologic) results at the two recording days, yielding an overall reproducibility of 70%. The limits of agreement for RI at day 2 were 0.2-3.3 times the initially obtained value at day 1. No difference was found in terms of reproducibility between groups with and without esophageal mucosal changes (erythema and esophagitis). No significant difference was noted in the association between pH monitoring and macroscopic esophageal mucosal changes between the two recordings days. In conclusion, a considerable intraindividual variability in reflux parameters was observed between the measurements from day 1 to day 2. This physiologic variability should be taken into consideration when evaluating gastroesophageal reflux disease in infants and children by means of pH monitoring. The day-to-day variability limits the use of simultaneous pH monitoring and dietary challenges as a procedure to identify a possible causative relation between GERD and dietary allergy/intolerance.

Adolescent↗

PubMed2000

Reproducibility of measurements of exhaled NO, and cell count and cytokine concentrations in induced sputum.

Sputum induction is a noninvasive, well-tolerated method for studying airway inflammation. When induction with hypertonic saline is repeated at short time-intervals (<24 h), the cell profile of sputum has not been reproducible. To determine the proper interval between sampling cell profiles and cytokine contents of sputum samples that had been induced 48 h apart, were compared. In addition, the inducible nitric oxide synthase (iNOS) expression of sputum cells was compared to the levels of exhaled nitric oxide (NO). Sputum induction and measurement of exhaled NO was performed in 31 healthy nonatopic volunteers. Cell differentials were counted. Concentrations of interleukin (IL)-4, IL-6, tumour necrosis factor (TNF)alpha, eosinophil cationic protein (ECP) were measured in sputum supernatant, and iNOS was determined. Reproducibility of cell counts was high (r=0.836 total cells, r=0.762 neutrophils, r=0.966 eosinophils, r=0.742 macrophages). IL-4 (r=0.398), IL-6 (r=0.566), TNFalpha (r=0.658) and ECP (r=0.501) were also less reproducible in healthy volunteers. Consistent with the low levels of NO in the exhaled air (18.5+/-2.6 ppb and 19.3+/-2.8 parts per billion (ppb) on the two study days, r=0.976, p=0.0000), expression of iNOS was not detected. In conclusion, in healthy subjects, induced sputum cell counts are reproducible. Even though the success rate in nonatopic populations is relatively low, sputum induction appears to be a valid method for detecting inflammatory changes within the airways, when being performed 48 h apart.

Administration, Inhalation↗

PubMed2005

Breast carcinoma malignancy grading by Bloom-Richardson system vs proliferation index: reproducibility of grade and advantages of proliferation index.

Questions of reproducibility and efficacy of histologic malignancy grading relative to alternative proliferation index measurements for outcome prediction remain unanswered. Microsections of specimens from the Cooperative Breast Cancer Tissue Resource (CBCTR) were evaluated by seven pathologists for reproducibility of grade and classification. Nuclear figure classification was assessed using photographs. Grade was assigned by the Bloom-Richardson method, Nottingham modification. Proliferation index was evaluated prospectively by deoxyribose nucleic acid precursor uptake with thymidine (autoradiographic) or bromodeoxyuridine (immunohistochemical) labeling index using fresh tissue from 631 node-negative breast cancer patients accessioned at St Luke's Hospital. A modified Nottingham-Bloom-Richardson grade was derived from histopathologic data. Median post-treatment observation was 6.4 years. Agreement on classification of nuclear figures (N=43) was less than good by kappa statistic (kappa=0.38). Grade was moderately reproducible in four trials (N=10,10,19, 10) with CBCTR specimens (kappa=0.50-0.59). Of components of Bloom-Richardson grade, agreement was least for nuclear pleomorphism (kappa=0.37-0.50), best for tubularity (kappa=0.57-0.83), and intermediate for mitotic count (kappa=0.45-0.64). Bloom-Richardson grade was a univariate predictor of prognosis in node-negative St Luke's patients, and was improved when mitotic count was replaced by labeling index (low, mid, or high). When labeling index was added to a multivariate model containing tumor size and vessel invasion, grade was no longer a significant predictor of tumor-specific relapse-free or overall survival. Mitotic index predicted best when intervals were lowered to 0-2, 3-10, and >10 mitotic figures per ten 0.18 mm(2) high-power fields. We conclude that Nottingham-Bloom-Richardson grades remain only modestly reproducible. Prognostically useful components of grade are mitotic index and tubularity. The Nottingham-Bloom-Richardson system can be improved by lowering cutoffs for mitotic index and by counting 20-30 rather than 10 high-power fields. Measurement of proliferation index by immunohistochemically detectable markers will probably give superior prognostic results in comparison to grade.

Breast Neoplasms↗

PubMed2004

Reproducibility and validity of coffee and tea consumption in Italy.

OBJECTIVE: The reproducibility and validity of coffee, decaffeinated coffee and tea intake has not been adequately studied, particularly in Italy, where coffee drinking is peculiar in terms of type and amount of coffee consumed. DESIGN: We compared coffee and tea consumption, measured by two interviewer-administered food frequency questionnaires (FFQ), with average intake derived from two 7-day dietary (DD) records (the reference method) on 395 volunteers. The Pearson correlation coefficients (r) were used to assess both reproducibility and validity of information on coffee intake. RESULTS: A satisfactory level of reproducibility and validity of the pattern consumption was observed for coffee, decaffeinated coffee and tea. The reproducibility for both sex combined showed r of 0.74-0.78 for coffee, 0.57-0.65 for decaffeinated coffee and 0.61-0.67 for tea. The validity was about 0.70 for coffee, around 0.58 for decaffeinated coffee and 0.56-0.60 for tea intake. CONCLUSIONS: The FFQ is a satisfactorily reliable and valid instrument for collecting information on coffee, decaffeinated coffee and tea intake.

Adult↗

PubMed2006

Intersubject variability and reproducibility of 15O PET studies.

Oxygen-15 positron emission tomography (15O PET) can provide important data regarding patients with head injury. We provide reference data on intersubject variability and reproducibility of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolism (CMRO2) and oxygen extraction fraction (OEF) in patients and healthy controls, and explored alternative ways of assessing reproducibility within the context of a single PET study. In addition, we used independent measurements of CBF and CMRO2 to investigate the effect of mathematical correlation on the relationship between flow and metabolism. In patients, intersubject coefficients of variation (CoV) for CBF, CMRO2 and OEF were larger than in controls (32.9%+/-2.2%, 23.2%+/-2.0% and 22.5%+/-3.4% versus 13.5%+/-1.4%, 12.8%+/-1.1% and 7.3%+/-1.2%), while CoV for CBV were lower (15.2%+/-2.1% versus 22.5%+/-2.8%) (P<0.001). The CoV for the test-retest reproducibility of CBF, CBV, CMRO2 and OEF in patients were 2.1%+/-1.5%, 3.8%+/-3.0%, 3.7%+/-3.0% and 4.6%+/-3.5%, respectively. These were much lower than the intersubject CoV figures, and were similar to alternative measures of reproducibility obtained by fractionating data from a single study. The physiological relationship between flow and metabolism was preserved even when mathematically independent measures were used for analysis. These data provide a context for the design and interpretation of interventional PET studies. While ideally each centre should develop its own bank of such data, the figures provided will allow initial generic approximations of sample size for such studies.

Adolescent↗

PubMed1998

Dynamic vessel wall properties and their reproducibility in subjects with increased cardiovascular risk.

OBJECTIVE: To determine reproducibility figures of dynamic arterial wall properties such as cross-sectional compliance (CC) and distensibility (DC) in subjects with increased cardiovascular risk, in comparison with healthy adults. METHODS: A total of 34 persons were divided into three groups with varying cardiovascular risk factors. Diameters (D) and diameter changes (deltaD) during the heart cycle of both common carotid (CCA) and right common femoral (CFA) arteries were measured by a vessel wall movement detector system. Blood pressures (BP) were recorded non-invasively by a semi-automated oscillometric device. CC (=piD(deltaD/2deltaP) in unit mm2/kPa) and DC (=2deltaD/D)/deltaP in unit 10(-3)/kPa) were calculated from the above-mentioned parameters. Measurements were performed twice during one visit and twice again with a time interval of at least 3 days to determine intra-observer intra- and intersession variability. RESULTS: Reproducibility figures of CC and DC of the CCA varied between 8 and 12%, and between 13 and 22% for the CFA. Intra-observer intra- and intersession variability were similar in the three groups. CONCLUSIONS: In our studies the reproducibility of dynamic vascular wall properties determined by ultrasound was good. Despite differences in the absolute values for CC and DC in groups with increased cardiovascular risk, mean reproducibility figures remained at a similar level (8-12%) as in healthy volunteers.

Adult↗