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Results for “Repeatability and Reproducibility”

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PubMed1996

Improvement of cardiac imaging in electrical impedance tomography by means of a new electrode configuration.

Until now, electrical impedance tomography (EIT) has been used for cardiac imaging with the electrodes attached transversally at the level of the fourth intercostal space at the anterior side. However, the results obtained with this electrode configuration have been disappointing. The aim of the present study was to improve the measurement design of EIT for cardiac imaging. Therefore, magnetic resonance imaging (MRI) scans were analysed in two healthy subjects to determine the optimum anatomical plane in which atria and ventricles are clearly visually separated. From these findings, we proposed a new oblique plane at the level of the ictus cordis anteriorly and 10 cm higher posteriorly. EIT pictures obtained in the oblique plane revealed a better visual separation between the ventricles and atria than with the electrodes attached in the transverse plane. Comparison between volume changes measured by means of MRI and impedance changes in different regions of interest measured with EIT were performed with the electrodes in the proposed oblique plane. Ventricular and atrial volume changes measured by MRI show the same pattern as do impedance changes measured by EIT. Furthermore, we assessed the reproducibility and validity of the oblique electrode configuration in ten healthy mate volunteers during rest and during exercise compared with the currently used transverse electrode configuration. The reproducibility coefficient assessed from repeated measurements with the electrodes attached in the oblique plane was 0.98 at rest and 0.85 during exercise. For the transverse plane the reproducibility coefficient was 0.96 at rest and 0.66 during exercise. The well-known increase in stroke volume during exercise is 40% in healthy subjects. The increase in impedance change during exercise compared with rest was 34 +/- 13% (20-59%) for the oblique plane and 68 +/- 57% (13-140%) for the transverse plane. From these results we infer that the stroke volume is assessed more accurately by using the oblique plane. From these findings, we conclude that the oblique plane improved the cardiac measurements, because (i) a better spatial separation of the heart compartments is obtained, (ii) the results are more reliable and (iii) measurements during exercise are more accurate with the electrodes attached in an oblique plane.

Cardiography, Impedance↗

PubMed2000

Sensitivity and limitations of high throughput fluorescent microsatellite analysis for the detection of allelic imbalance: application in lung tumors.

We have used two hexaplex fluorescent microsatellite assays and analysis on an automatic sequencer to determine allelic imbalance in lung tumors. The markers used are located close to tumor-suppressor genes, DNA repair genes and regions frequently lost in lung cancer. We present a reference interval and quantify the reproducibility of the assays as assessed by multiple repeat reactions for normal DNAs. The cut-off value was calculated to 0.77 (23% reduction of one allele intensity) which, to the best of our knowledge, is currently the lowest reported cut-off. Using these parameters we analysed 85 lung carcinomas. Eighty-three samples (97.6%) showed allelic imbalance in at least one locus. It is of note that by using a selection of only 6 markers, imbalance was detected in 81 (95.2%) of the samples. Loci 9p21 and 9p23 exhibited the greatest imbalance (77% and 75% respectively). The fractional allele loss (FAL) for the 3p markers examined was greater in squamous cell carcinomas than adenocarcinomas (t-test, p=0.0001) while no such difference was observed for 9p. The degree of imbalance of different markers within the same sample was divergent, indicating heterogeneity of genomic status (losses, amplifications, aneuploidy) in these tumors. In conclusion, we have established a robust experimental platform with high throughput, sensitivity and specificity for the detection of allelic imbalance in lung tumors. Such assays may be useful for the detection of allelic imbalance in clinical samples to trace genetically abnormal cells and thus assist in the identification of individuals at a high risk for developing lung cancer.

Aged↗

PubMed2003

Assessment of reproducibility of measures of intraocular pressure and central corneal thickness in young white adults over a 16-h time period.

PURPOSE: The aims of this study were to obtain clinical measures of intraocular pressure (IOP) and central corneal thickness (CCT) and during waking hours to further assess both the nature of diurnal changes, and the reproducibility of any possible association between the two measures. METHODS: Fifteen white (Norwegian) healthy young adult subjects aged 20-29 years had IOP and CCT measures made, using a non-contact specular microscope and non-contact tonometry (NCT), every hour over a period of 16 h, starting at 06.30 hours. The experiment was repeated on two successive days. RESULTS: The average NCT readings were 12.5 and 11.4 mmHg for days 1 and 2, while pachometry averages were 0.518 and 0.514 mm. The range of NCT values, for any set of readings, averaged 2 mmHg, while this range was 0.014 mm for CCT measures. The reproducibility of these measures, as estimated by the coefficient of variation (COV) was 7.2% for NCT and 1.0% for pachometry measures. The COV for tonometry was inversely proportional to the actual values of these measures. A significant time-related decline in tonometry values was seen over day 1 but not day 2. Pachometry values declined very rapidly over the first hour in both sessions and were essentially constant for the rest of the sessions. The strongest association between pachometry data and NCT measures was noted around midday (12.30 hours) on both sessions. CONCLUSIONS: These studies confirm that the reproducibility (repeatability) of NCT and pachometry are substantially different. It is suggested that this aspect of tonometry needs to be taken into account, especially where there are lower values, when considering the possible impact of corneal thickness on tonometry measures and their interpretation. These types of effects need to be further assessed in older patients with ocular hypertension, or other glaucoma suspects.

Adult↗

PubMedDate not supplied

Comparison of visual analog and numeric scoring scales for assessing intraoperative mesenteric portovenography.

A visual analog scale and a numeric scoring scale were designed for the assessment of dynamic intraoperative mesenteric portovenography in the dog and cat. Two independent observers evaluated both scoring scales for reproducibility (differences between observers) and repeatability (within-observer differences) in the assessment of 60 trial portovenograms. Agreement (interchangeability) of both scales was evaluated by comparing the scores obtained in the assessment of 200 portovenograms obtained from 100 dogs and cats. There was no statistical difference between the two observers when scoring the same portovenogram for either the visual analog scale (p = .730, reproducibility coefficient = 17.85 units) or the numeric scoring scale (scores identical, reproducibility coefficient = 0). There was no statistical difference, for either of the observers, when the same portovenogram was assessed on two separate occasions using the visual analog scale (observer 1, p = .35, repeatability coefficient = 17.93 units; observer 2, p = .42, repeatability coefficient = 8.27 units) or the numeric scoring scale (scores given by both observers were identical, repeatability coefficient = 0 for both observers). The results of comparison between the visual analog scale and numeric scoring scale confirmed that the two scoring systems were not directly interchangeable. Although both scoring systems demonstrated good reproducibility and repeatability, the numeric scoring scale possessed a number of inherent deficiencies that suggested it was not the method of choice for the assessment of the subjective data obtained from dynamic intraoperative mesenteric portovenography.

Animals↗

PubMed1993

Comparison of dot filter hybridization, Southern transfer hybridization, and polymerase chain reaction amplification for diagnosis of anal human papillomavirus infection.

The detection and classification of human papillomavirus (HPV) by a consensus primer polymerase chain reaction (PCR) technique were compared with detection and classification by dot filter hybridization (DFH) and Southern transfer hybridization (STH). PCR detected HPV in 87% of specimens; the detection rates for DFH and STH were 51% and 49%, respectively. The specific HPV types detected by STH were also detected by PCR in 90% of specimens. However, 75% of the samples positive for unclassified HPV by STH were typed by PCR. PCR results were reproducible, as assessed by repeat analysis (96% agreement), by analysis of paired same-day specimens (89% agreement), and by interlaboratory analysis (88% agreement). PCR is a sensitive, specific, and reproducible test for HPV detection and classification in clinical and epidemiologic studies.

Anus Diseases↗

PubMed1997

Reproducibility of dual-energy X-ray absorptiometry in the upper extremities in stroke patients.

Bone mineral loss after stroke in affected extremities can increase the prevalence of fractures that interrupt the rehabilitation programme and lower the level of activity. In stroke rehabilitation, precise bone mineral measurement is needed in order to assess the risk of fractures. We defined five regions-of-interest of the upper extremity (proximal humerus, distal forearm, distal radius, distal ulna and hand) consistently, so that the position was comfortable for hemiplegic patients to maintain during the measurement. The aim of this study was to determine whether our method using dual-energy X-ray absorptiometry is useful in hemiplegic patients. Ten normal subjects and 15 hemiplegic patients were studied. In normal subjects the reproducibility of our method was evaluated by repeated measurements of both the right and left sides. In hemiplegic patients the reproducibility was evaluated by repeated measurements of the affected side. The coefficient of variation (CV) values were obtained for BMD (0.7-1.7%) and BMC (0.7-2.3%) in normal subjects, and BMD (1.3-2.1%) and BMC (1.7-5.4%) in hemiplegic patients. The CV for the side-to-side BMD and BMC ratios in the normal subjects ranged from 1.1% to 2.2% and from 1.8% to 3.1%, respectively. Our study shows that the reproducibility of our method is sufficient for application to hemiplegic patients.

Absorptiometry, Photon↗

PubMed1986

[Dynamics of the indices of spirometry and bicycle ergometry in stenocardia patients undergoing repeated studies].

A study of reproducibility and patterns of change in 7 control bicycle and respiration ergometric tests in 14 coronary anginal patients demonstrated consistent change in stress tolerance and gaseous exchange: a rapid adaptation period (first 2 or 4 tests) when stress tolerance, ventilation and maximum oxygen uptake increased significantly, and a slow adaptation period (most later tests) when tolerance grew gradually, while oxygen consumption first dropped and then stabilized above the baseline. Accidental stress tolerance variation exceeded 1 step in 20% of patients, obviously due to their inability to adapt to the testing procedure. It is suggested that pharmacodynamic studies of antianginal drugs, making use of bicycle and respiration ergometry can only be conducted in the slow adaptation period, provided the individuals showing wide spontaneous variability are excluded from the study.

Adult↗

PubMed1997

Reliability of diagnostic tests.

The reliability of a diagnostic test depends on the accuracy and reproducibility of the test results. The accuracy is defined by comparing the test results with a final true diagnosis. The predictive values are here the most important clinical measures. Since it may be impossible to establish a final true diagnosis the reliability must in some cases be measured by a determination of reproducibility. The reproducibility is measured by comparing results of repeated examinations of the same patient. The reproducibility is measured by the use of the kappa coefficient which adjusts the observed agreement for expected chance agreement. A study of reliability of a diagnostic test should fulfill the same methodological requirements as other clinical studies. Both the predictive values and the kappa coefficient are supposed to depend on the prevalence and this should be noticed when results of different studies are compared. Reliability of diagnostic tests is often poor and scientific development of how to improve clinicians' diagnostic practice is much needed.

Analysis of Variance↗

PubMedDate not supplied

Validation of a method for determination of phospholipase A2 and melittin in bee venom preparations by capillary electrophoresis.

A method was validated for the determination of the 2 main components of bee venom, phospholipase A2 and melittin, by capillary electrophesis (CE). Optimum resolution and selectivity were attained with a running electrolyte of 150 mM phosphoric acid, pH 1.8. The repeatability and day-to-day reproducibility of the migration times were better than 0.36 and 2.8%, respectively. The repeatability and day-to-day reproducibility of the normalized peak areas were better than 1.3 and 2.6%, respectively. The response of the UV detector at 190 nm was linear over < 2 concentration decades, from 0.05 to 1.5 mg/mL, with correlation coefficients of 0.9994 for phospholipase A2 and 0.9997 for melittin. The limits of detection and quantitation were 4.5 and 15 microg/mL, respectively, for phospholipase A2 and 1.6 and 6 microg/mL, respectively, for melittin. The reproducibility of the measurements with 2 different CE instruments was satisfactory; the mean concentration and relative standard deviation (RSD) values for phospholipase A2 and melittin were 14.4% (RSD, 1.3%) and 51.4% (RSD, 1.1%), respectively, with instrument I; the corresponding values with instrument II were 14.5% (RSD, 2.8%) and 52.3% (RSD, 2.2%). The accuracy was estimated by comparison with a liquid chromatographic (LC) method. Differences between the CE and LC measurements were attributed to irreversible adsorption of the analytes on the LC column. The recoveries of phospholipase A2 and melittin with the CE method were 98.8 and 101.7%, respectively.

Bee Venoms↗

PubMed2004

Capillary electrochromatography with polymeric continuous beds synthesized via free radical polymerization in aqueous media using derivatized cyclodextrins as solubilizing agents.

A novel synthetic route to amphiphilic acrylamide-based monolithic stationary phases for capillary electrochromatography (CEC) employing water-soluble cyclodextrins as solubilizing agents was explored. N,N'-Octamethylenebisacryamide and N,N'-dodecamethylenebisacryamide were synthesized and their solubilization in aqueous solution with derivatized and underivatized cyclodextrins of different cavity size was studied. Amphiphilic stationary phases were synthesized by free radical copolymerization of the bisacrylamide-cyclodextrin host-guest complexes with hydrophilic monomers and an additional hydrophilic cross-linker in aqueous solution. Complex formation in solution and removal of the complexed cyclodextrin from the polymer during synthesis was studied with 1H-NMR and solid state 13C-NMR spectroscopy and cyclodextrin-modified micellar electrokinetic chromatography. The impact of the incorporated alkylene groups in the acrylamide-based macroporous polymer on retention was studied with neutral solutes by CEC in the normal-phase elution mode and in the reversed-phase elution mode. Batch-to-batch reproducibility of the synthesis procedure and day-to-day repeatability of the separations achieved were investigated. With these capillaries, a sufficiently high electroosmotic flow velocity, a high reproducibility and repeatability of separation parameters and high plate numbers (up to 200,000 m(-1) were obtained.

Chromatography, Micellar Electrokinetic Capillary↗

PubMedDate not supplied

Quantification of ischemic stress during repeated coronary artery occlusion in the dog. A method for validation of therapeutic effects. II. Reproducibility of the release and uptake of electrolytes and substrates.

As criterion for the degree of ischemic stress on myocardium during repeated coronary artery occlusion, the reproducibility of the release of potassium, lactate and inorganic phosphate in the early reperfusion period was examined. On 20 anaesthetized open-chest mongrel-dogs, local ischemia was induced by intermittent occlusion of the LAD artery. In each experiment the artery was occluded for 3 min 4 to 6 times with intervals of 45 min. Just before beginning, at the end of occlusion and after 5 min of reperfusion, arterial and coronary venous blood was collected simultaneously. Additionally, 3 ml of blood were withdrawn by syringe-pumps during the first minute of reperfusion. Intra-individually, the following standard-deviations were found in a representative experiment with 5 occlusions: potassium +/- 7% (22.62 +/- 1.6 mumol/min); inorganic phosphate +/- 9% (19.82 +/- 2.06 mumol/min); lactate +/- 11% (55.38 +/- 5.93 mumol/min). Interindividually, the correlation between the release of these markers and the perfusion bed of the ligated artery led to coefficients of about r approximately 0.88. On an average, per gram ischemic tissue/wet weight 0.74 mumol potassium, 0.6 mumol inorganic phosphate and 1.98 mumol lactate were released. The ratios between the releases remained constant independent of the size of ischemic area. An even closer correlation with coefficients of about r approximately 0.97 was found between the O2-debt in the occlusion period. Based on a synoptic assessment of metabolic and energetic parameters, this experimental model may render more detailed information on pharmacological interventions during ischemic stress.

Animals↗

PubMed1995

Precision of laser Doppler scanning in clinical use.

Reactions of the cutaneous microcirculation to local stimuli have been quantitated in terms of area of erythema (planimetry), change in colour (colorimetry) and time-dependent changes in perfusion (one-dimensional laser Doppler fluxmetry (LDF)). Using the new technique of laser Doppler scanning (LDS) it is now possible to quantify and demonstrate two-dimensional patterns of microvascular perfusion in terms of intensity and extent. The precision of this new technique was compared with the previously established techniques by examining the reactions of 15 healthy volunteers to the intracutaneous injection of carbacholin and isotonic NaCl solutions. Both stimuli were applied paravertebrally, on the left and right side. Reactions were examined after 10 min. As a control for temporal reproducibility the examination was repeated on another day. All methods allowed the differentiation of reactions to carbacholin from those to NaCl (P < or = 0.0001). Only colorimetry and LDS provided data that were unequivocally reproducible when comparing both sides (r > or = 0.78). Using LDF or planimetry, reproducibility of values was lower (r < or = 0.58). When looking at measurements performed on different days, only values of LDS were reproducible (r > or = 0.77). Hyperaemic areas seen with LDS were significantly larger than those determined by planimetry. Results of LDS are reproducible spatially and temporally: the technique will allow time-course observations of skin reactions that are accompanied by medium-term changes in perfusion.

Adult↗

PubMed1993

Transcranial magnetic stimulation mapping of the motor cortex in normal subjects. The representation of two intrinsic hand muscles.

The TMS-mapped representations of two intrinsic hand muscles, abductor pollicis brevis (APB) and abductor digiti minimi (ADM), were quantified using a transcranial magnetic stimulation (TMS) mapping technique in 10 right handed and 6 left handed subjects. A 50 mm diameter figure eight coil was used. Stimulus sites were located using a latitude/longitude based coordinate system, stimulus intensity was threshold-adjusted and stimuli were applied during controlled low-level (10%) voluntary contraction of the target muscles. Maps of the corticomotor representation were generated by fitting a continuously defined three dimensional function to the data obtained from stimulation at specific scalp sites, and projecting this function onto a two dimensional surface using a radial projection. It was found that the mapped representations of APB and ADM were large and overlapping but that there was a statistically significant separation of the two areas, the APB area being more laterally placed than the ADM area. The TMS-mapped representations of the two muscles showed no significant interhemispheric differences and were similar in left and right handed subjects. Rotation of the magnetic coil through 90 degrees resulted in medial shift and elongation of the TMS-mapped representations but there was no change in the relative positions of the two areas. The TMS-mapped representations were found to be very reproducible when mapping was repeated after intervals of up to 181 days. The present technique of TMS mapping allows the representation of individual hand muscles in the primary motor cortex to be reliably and reproducibly mapped and should prove useful for further studies of the physiology and pathophysiology of the motor cortex in man.

Adult↗

PubMed2006

High-performance liquid chromatography determination of phenyllactic acid in MRS broth.

Phenyllactic acid (PLA) is an organic acid produced by some strains of lactic acid bacteria (LAB) and concentrations higher than 7.5 mg/ml inhibit growth of moulds and yeasts. Since PLA can be used to select LAB, a rapid, simple and cheap method for its determination is desirable. Typical methods for its analysis in broth are time-consuming, analytically complicated, and have poor recoveries. Herein we propose a simple and rapid method that does not require extraction, but only microfiltration of broth before injection in HPLC. The improved chromatographic conditions allow separation and quantification of PLA with a recovery of 98.7%. The method is highly reproducible with an intraday repeatability of the total peak area of 2.00%, while an interday repeatability of 2.69%.

Chromatography, High Pressure Liquid↗

PubMed2003

Phantom validation of multichannel magnetocardiography source localization.

Multichannel magnetocardiography (MMCG) is used clinically for noninvasive localization of the site of origin of cardiac arrhythmias. However, its accuracy in unshielded environments is still unknown. The aim of this study was to test the accuracy of three-dimensional localization of intracardiac sources by means of MMCG in an unshielded catheterization laboratory using a saline-filled phantom, together with a nonmagnetic catheter designed for multiple monophasic action potential recordings in a clinical setting. A nine-channel direct current superconducting quantum interference device (DC-SQUID) system (sensitivity fT/Hz0.5) was used for MMCG from 36 points in a measuring area of 20 x 20 cm. The artificial sources to be localized were dipoles embedded in the distal end of the catheter, placed 12 cm below the sensor's plane. Equivalent current dipoles, effective magnetic dipoles, and distributed currents models were used for the inverse solution. The localization error was estimated as the three-dimensional difference between the physical position of the tip of the catheter and the three-dimensional localization of the dipoles derived by means of the inverse solution calculated from MMCG data. The reproducibility was tested by repeating the MMCG after repositioning the phantom and the measurement system. The average location error of the catheter dipole was 9 +/- 4 mm and was due primarily to imprecise depth estimation. Localization was reproducible within 0.73 mm. The distributed currents model provided an accurate image of current distribution centered over the catheter tip. The authors conclude that MMCG estimation is accurate enough to guarantee proper localization of cardiac dipolar sources even in an unshielded clinical electrophysiological laboratory.

Arrhythmias, Cardiac↗

PubMed1996

The yield of head-up tilt testing is not significantly increased by repeating the baseline test.

BACKGROUND AND HYPOTHESIS: Head-up tilt is widely used in evaluating patients with syncope. Data suggest that baseline tilt without isoproterenol is associated with few (< or = 10%) positive results in normals. However, there is considerable day-to-day variability in patients with syncope, resulting in low reproducibility. We hypothesized that repeating the baseline tilt would increase the total number of positive responses. METHODS: In all, 193 patients with syncope of unknown etiology prospectively underwent serial baseline tilt (Tilt-1 and Tilt-2) at 70 degrees for 25 min on two consecutive days. RESULTS: Of 193 patients, 39 (20%) had a positive Tilt-1. Of these, 19 had a positive Tilt-2, (positive concordance rate: 19/39 = 49%). Of 154 patients with a negative Tilt-1, 145 had a negative Tilt-2 (negative concordance rate: 142/151 = 94%). Only 9 of 154 patients (6%) with a negative Tilt-1 had a positive Tilt-2. Thus, the yield increased from 20% (39/193) after Tilt-1, and to 25% (48/193) after Tilt-1 plus Tilt-2, p = NS. CONCLUSIONS: (1) Reproducibility of a positive Tilt-1 is moderate. (2) Reproducibility of a negative Tilt-1 is high. (3) Repetition of tilt in patients with a negative Tilt-1 does not significantly increase the number of positive results.

Blood Pressure↗

PubMed2004

Human DNA polymerase-eta, an A-T mutator in somatic hypermutation of rearranged immunoglobulin genes, is a reverse transcriptase.

We have proposed previously that error-prone reverse transcription using pre-mRNA of rearranged immunoglobulin variable (IgV) regions as templates is involved in the antibody diversifying mechanism of somatic hypermutation (SHM). As patients deficient in DNA polymerase-eta exhibit an abnormal spectrum of SHM, we postulated that this recently discovered Y-family polymerase is a reverse transcriptase (RT). This possibility was tested using a product-enhanced RT (PERT) assay that uses a real time PCR step with a fluorescent probe to detect cDNA products of at least 27-37 nucleotides. Human pol-eta and two other Y-family enzymes that are dispensable for SHM, human pols-iota and -kappa, copied a heteropolymeric DNA-primed RNA template in vitro under conditions with substantial excesses of template. Repeated experiments gave highly reproducible results. The RT activity detected using one aliquot of human pol-eta was confirmed using a second sample from an independent source. Human DNA pols-beta and -mu, and T4 DNA polymerase repeatedly demonstrated no RT activity. Pol-eta was the most efficient RT of the Y-family enzymes assayed but was much less efficient than an HIV-RT standard in vitro. It is thus feasible that pol-eta acts as both a RNA- and a DNA-dependent DNA polymerase in SHM in vivo, and that Y-family RT activity participates in other mechanisms of physiological importance.

Base Sequence↗

PubMed1984

Comparison of antibiotic susceptibility results obtained with Adatab and disc methods.

Strains of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, faecal streptococci, Proteus spp, and Klebsiella spp were distributed on two occasions to two groups of laboratories, one using a commercially produced break point method (Adatab, Mast Laboratories Ltd) and the other using a disc method for susceptibility testing. Minimum inhibitory concentrations of a range of antibiotics were determined for each of the strains in the Division of Microbiological Reagents and Quality Control and a correct result of sensitive or resistant was assigned where possible to each combination of strain and antibiotic. Laboratories were asked to determine the susceptibility of the strains to those antibiotics that they would test in routine practice. Results from each laboratory were compared with the correct results. The overall error rates obtained with the Adatab and disc methods, 8% and 8.2% respectively, were not significantly different. Fewer errors were made with trimethoprim, ticarcillin, and nitrofurantoin by laboratories using Adatabs than those using discs. Fewer errors were made with gentamicin by laboratories using discs than those using Adatabs. There was no significant difference between the two groups of laboratories in reproducibility of results on repeated testing of the same strains. Laboratories using Adatabs used a wide range of different break point concentrations. The Adatab method appeared to offer no overall advantages in terms of reduced error rates or increased reproducibility of results with the strains tested.

Anti-Bacterial Agents↗