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Results for “Repeatability and Reproducibility”

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PubMed1991

Digital artery calibre measurement--a new technique of assessing Raynaud's phenomenon.

This study evaluated the use of a high frequency A-mode ultrasound scanner (CUTECH DM70) for monitoring the digital artery vasospasm of Raynaud's Phenomenon (RP). The technique was evaluated on 12 RP patients and 12 age and sex matched controls. The diameter of a single digital artery was measured in these subjects over a range of finger temperatures between 14-35 degrees C. The reproducibility of the measurements was assessed by repeating the procedure in two subjects (a control and an RP patient) on 5 separate days. The results confirmed that the technique is reproducible and monitored vasospasm occurring in all 12 RP patients. In the temperature range tested, none of the controls developed digital artery vasospasm. At finger temperatures greater than 25 degrees C the response to thermal stimuli of the digital arteries in RP patients and controls was similar. However, at temperatures less than 25 degrees C a marked vasoconstriction leading to complete digital artery closure was seen in the RP patients and not in the controls. This technique may prove useful in monitoring RP patients.

Adult↗

PubMed2006

Reliability and consistency of dark-adapted psychophysical measures in advanced eye disease.

PURPOSE: To establish reliable vision measures allowing functional monitoring in patients with severe vision loss. METHODS: Legally blind and normally sighted subjects were enrolled in a repeated-measures study to determine the reproducibility of psychophysical vision measures under scotopic conditions. The tests included dark adaptometry, dark-adapted, full-field flash testing, and dark-adapted macular thresholds, obtained by using a perimeter with 500- and 650-nm targets. Two to five test repetitions were performed on the better eye of each subject at monthly intervals. Subject groups included retinitis pigmentosa (RP; n = 33), macular disease (MD; n = 14), optic nerve disease (ON; n = 4), diabetic retinopathy (DR; n = 5), and other retinal diseases (OR; n = 9), and normally sighted control (CTL; n = 12). RESULTS: Dark adaptometry timing yielded mean coefficients of variation for subjects across all groups that averaged approximately 20% throughout the test. For dark-adapted perimetry, the coefficients of repeatability (CR(.95)) were <7 dB (CTL), <8 dB (OR), <6 dB (ON and RP), and <15 dB (MD). Full-field flash test CR(.95) by group varied from 5 to 15 dB, and most low-vision groups performed more reliably than CTL subjects. CONCLUSIONS: Dark-adapted psychophysical tests can provide reproducible vision measures in subjects with severe visual impairments, and these tests would be useful in monitoring outcomes in future clinical trials to reverse, halt, or slow vision loss. The most valuable measure of remaining vision was the dark-adapted, full-field flash test, as it produced repeatable results at all levels of vision loss and for all disease states included in this study.

Adult↗

PubMed1996

[Development of highly sensitive assay for detection of low serum level of PIVKA-II and its clinical usefulness].

PIVKA-II is well known as a tumor marker of hepatocellular carcinoma. We describe the adaptations to render a commercially available PIVKA-II immunoassay kit (Eitest MONO P-II: Eisai Co., Ltd, Tokyo) more sensitive and evaluated clinical usefulness of this highly sensitive assay for early diagnosis of hepatocellular carcinoma. We measured serum PIVKA-II concentrations with the Eitest kit as described for the kit. To measure serum PIVKA-II concentrations below the sensitivity limit of the Eitest kit (0.0625AU/ml), linearity was determined using a series of dilutions of standard antigen diluted in standard diluent, including PIVKA-II concentrations of 0.002, 0.004, 0.008, 0.016, 0.031, 0.0625AU/ml. The assay was found to be liner from 0.004AU/ml. In this way, one can detect as low PIVKA-II concentrations as 0.004AU/ml. The repeatability-assay coefficients of variation (CV%) obtained from sixteen repeated assays of four sera were distributed between 3.63 and 18.75% and the reproducibility-assay coefficients of variation (CV%) obtained from ten repeated assays of four sera were distributed between 6.27 and 14.04%. We determined the serial changes in serum PIVKA-II levels of two patients with hepatocellular carcinoma after the resection of hepatic tumor. In these patients, elevation of serum PIVKA-II level determined by the highly sensitive assay preceded the detection of relapse by imaging diagnostic procedures. In summary, the assay system we developed has good accuracy and reproducibility for assaying low concentrations of PIVKA-II in serum and is suitable for detecting small increases in PIVKA-II concentrations. This assay system may be useful to earlier detect a relapse of hepatocellular carcinoma.

Biomarkers↗

PubMed1997

Reproducibility of ventricular fibrillation characteristics in patients undergoing implantable cardioverter defibrillator implantation.

INTRODUCTION: The purpose of this study was to evaluate the immediate reproducibility of local electrogram characteristics recorded during repeated episodes of induced ventricular fibrillation (VF) in patients undergoing implantable cardioverter defibrillator (ICD) implantation. METHODS AND RESULTS: Power spectral analysis (using a fast Fourier transform algorithm) of electrograms recorded during 3 seconds of VF were analyzed in 24 patients undergoing ICD implantation using a Medtronic Transvene lead. Patients had 2 to 7 episodes of VF that were induced during defibrillation threshold testing. VF was induced by burst pacing (n = 20) or T wave shock (n = 4). Simultaneous electrograms during VF were recorded from a Medtronic Transvene lead with the following configurations: (1) a narrow spaced (12 mm) dedicated bipole used clinically for sensing; (2) a unipolar electrogram from the right ventricular coil; and (3) a widely spaced (18.3 mm) integrated bipole using the distal tip and the coil. Intraclass correlation coefficients (ICCs) were determined to examine the reproducibility of these VF characteristics among VF episodes in each patient. Recordings from both bipolar configurations had ICCs from 0.40 to 0.55, whereas unipolar recordings ICCs were below 0.40. Reproducibility was similar for dedicated and integrated recordings. CONCLUSIONS: Frequency characteristics of repeated episodes of VF induced in the same subjects show fair-to-good but not excellent reproducibility. Bipolar recordings were far more reproducible than unipolar recordings, but both bipolar configurations had similar reproducibility. These findings have implications for both the pathophysiology of induced VF and the design of VF detection algorithms.

Adult↗

PubMed1998

Acceleration of mammary tumorigenesis by exposure of 7,12-dimethylbenz[a]anthracene-treated female rats in a 50-Hz, 100-microT magnetic field: replication study.

In view of the methodological problems of epidemiological studies on associations between residential and occupational exposures to 50/60-Hz magnetic fields (MF) and increased incidence of cancers, laboratory studies are necessary to determine if 50/60-Hz MF can affect cancer development or growth. Recently, it was reported that alternating (50-Hz) MF of low flux density (100 microT) increase tumor growth and progression in a model of breast cancer in female rats in which mammary tumors were induced by the chemical carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). The objective of the present study was to determine if a replicate experiment carried out in the same laboratory under the same experimental conditions yields a significant increase in tumor development and growth of similar magnitude. For the MF experiment, a group of 99 female Sprague-Dawley rats was exposed to a homogeneous horizontally polarized MF for 24 h/d (minus time for weighing, tumor palpation, cage cleaning, cage rotation), 7 d/wk; another group of 99 rats was sham exposed. DMBA was administered intragastrically at a dose of 5 mg/rat at the first day of exposure and at weekly intervals thereafter up to a total dose of 20 mg/rat. Duration of MF or sham exposure was 91 d. In both MF-exposed and sham-exposed rats, the first tumors could be recorded 6 wk after the initial DMBA application. At 9 wk after DMBA application, the group of MF-exposed rats exhibited significantly more animals with tumors than the sham-exposed group. This significant difference in the rate of tumor development was observed throughout the subsequent period of exposure. After autopsy, the incidence of macroscopically visible mammary tumors was 62% in controls, but 83% in MF-exposed rats, with the 35% difference between groups being statistically significant. Data substantiate that long-term exposure of DMBA-treated female Sprague-Dawley rats in an alternating MF of low flux density promotes the development and growth of mammary tumors, thus indicating that MF exposure exerts tumor-promoting and/or copromoting effects. Furthermore, the data show that the effects of MF exposure in the DMBA breast cancer model are reproducible if the same experiment is repeated in the same laboratory.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2004

Reproducibility of blood pressure variability, white-coat effect and dipping pattern in untreated, uncomplicated and newly diagnosed essential hypertension.

OBJECTIVE: To investigate the reproducibility of blood pressure (BP) variability, white-coat effect (WCE) and nocturnal dipping pattern in untreated patients with uncomplicated essential hypertension using 24-hour ambulatory BP monitoring (ABPM). METHODS: Seventy-five newly diagnosed, untreated essential hypertensive subjects (54 men, 21 women 47.6 +/- 9.3 years) were recruited for the study based on conventional measured BP from a total of 180 patients referred for ABPM. Of these, 65 patients underwent repeated ABPM after 4 weeks observation without treatment. Reproducibility of BP, nocturnal dipping pattern, WCE and BP variability were assessed using different methods. RESULTS: The average 24-hour BP (140.8 +/- 11.9/91.8 +/- 6.4 vs. 140.5 +/- 14.5/90.7 +/- 7.6 mmHg, ns) or PP (49.6 +/- 10.8 vs. 49.8 +/- 9.8 mmHg, ns) did not change, nor did daytime BP or PP. The WCE diminished significantly during the observation period (reduction in SBP WCE delta8.2 +/- 12.5 mmHg, p < 0.0001, in DBP WCE, delta3.3 +/- 9.2 mmHg, p = 0.008 and in PP WCE delta4.8 +/- 11.2 mmHg, p = 0.002). Variability in SBP, DBP and PP decreased consistently and significantly during the observation period. The nocturnal dipping pattern was unchanged in 82% of the patients. In 12% non-dipping pattern was converted to dipping pattern after repeated measurement. CONCLUSION: Average ABPs are highly reproducible in patients with uncomplicated essential hypertension of limited duration. Similarly, nocturnal dipping pattern reproduced satisfactorily. These measures have important clinical applicability. The white-coat effect as well as variability are greatly attenuated during repeated measurements, and these measures may thus be of less utility in clinical practice.

Adult↗

PubMed2002

Electrophysiologic investigation in Brugada syndrome; yield of programmed ventricular stimulation at two ventricular sites with up to three premature beats.

INTRODUCTION: Numerous reports on the inducibility of ventricular tachyarrhythmias (VT) in patients with atypical right bundle branch block and right precordial ST-elevation (Brugada syndrome) are based on multicentre studies that have used different stimulation protocols. Therefore, we prospectively investigated the inducibility of VT in these patients using a uniform protocol. METHODS: In 41 consecutive patients (29 males) showing a pattern of right bundle branch block and ST-elevation, programmed ventricular stimulation was performed in the right ventricular apex with up to three premature stimuli at sinus rhythm and at four different paced cycle lengths (500, 430, 370, and 330 ms) until refractoriness was reached or reproducible induction of a sustained (>30s) VT occurred. If a VT was not reproducibly inducible, the same protocol was repeated in the right ventricular outflow tract. RESULTS: A history of life-threatening events defined as syncope (n=17) or aborted sudden cardiac death (n=13) was present in 30 patients (73%); 11 individuals were asymptomatic. Inducibility (68%) was similar between symptomatic (n=21, 70%) and asymptomatic patients (n=7, 64%). In 16 (39%) patients, VT were reproducibly inducible. If patients were only stimulated in the right ventricular apex, inducibility rate decreased to 39%. If only two premature beats at two sites were used it was as low as 32%. The mean coupling intervals of the second and third premature stimuli inducing sustained VT were short: 189+/-21 ms vs 186+/-22 ms, respectively. Forty-four percent of all patients (i.e. 64% of the inducible patients) had inducible VT only with coupling intervals shorter than 200 ms. CONCLUSIONS: The stimulation protocol markedly influences the extent of inducibility of VT in patients with right bundle branch block and ST-segment elevation. These findings question the significance of previous multicentre studies using different stimulation protocols and should have implications for further studies.

Adult↗

PubMed1999

High polymorphism level of genomic sequences flanking insertion sites of human endogenous retroviral long terminal repeats.

The polymorphism at the multitude of loci adjacent to human endogenous retrovirus long terminal repeats (LTRs) was analyzed by a technique for whole genome differential display based on the PCR suppression effect that provides selective amplification and display of genomic sequences flanking interspersed repeated elements. This strategy is simple, target-specific, requires a small amount of DNA and provides reproducible and highly informative data. The average frequency of polymorphism observed in the vicinity of the LTR insertion sites was found to be about 12%. The high incidence of polymorphism within the LTR flanks together with the frequent location of LTRs near genes makes the LTR loci a useful source of polymorphic markers for gene mapping.

Chromosome Mapping↗

PubMed1994

Estimation of adipose tissue mass by magnetic resonance imaging: validation against dissection in human cadavers.

The evaluation of adipose tissue distribution has become an essential component of investigations on the complications of obesity. However, a major limitation is lack of methodology for accurate estimation of adipose tissue mass in the different regions of the body. Therefore, we have tested the accuracy and precision of magnetic resonance imaging (MRI) as a method to measure adipose tissue mass in regions of the body not accessible with standard anthropometric methods. The mass of subcutaneous and intraabdominal adipose tissue estimated by MRI was compared with that obtained by direct weighing of the same adipose tissue compartments after dissection in human cadavers. MRI was performed on three unembalmed cadavers (two males, one female) who were subsequently dissected to isolate intraperitoneal, retroperitoneal, and subcutaneous adipose tissues. These same components were delineated by MRI. The results of the two methods were highly congruent. For the various compartments, the mean of the difference between the two methods was only 0.076 kg (95% confidence interval + 0.005 kg and + 0.147 kg). The "limits of agreement" between the two techniques were -0.066 kg and +0.218 kg. Multiple repeated estimates of mass of adipose tissue compartments were made to determine reproducibility of the MRI measurement; the coefficient of variation for repeated measures was below 14%. The results of this study show that MRI is an accurate and precise technique to evaluate adipose tissue mass in subcutaneous and intraabdominal compartments. Furthermore, MRI was found to be a valid method to separately evaluate the mass of intraabdominal subcompartments of intraperitoneal and retroperitoneal adipose tissue.

Abdomen↗

PubMed2000

Multicenter evaluation of epidemiological typing of methicillin-resistant Staphylococcus aureus strains by repetitive-element PCR analysis. The European Study Group on Epidemiological Markers of the ESCMID.

Rapid and efficient epidemiologic typing systems would be useful to monitor transmission of methicillin-resistant Staphylococcus aureus (MRSA) at both local and interregional levels. To evaluate the intralaboratory performance and interlaboratory reproducibility of three recently developed repeat-element PCR (rep-PCR) methods for the typing of MRSA, 50 MRSA strains characterized by pulsed-field gel electrophoresis (PFGE) (SmaI) analysis and epidemiological data were blindly typed by inter-IS256, 16S-23S ribosomal DNA (rDNA), and MP3 PCR in 12 laboratories in eight countries using standard reagents and protocols. Performance of typing was defined by reproducibility (R), discriminatory power (D), and agreement with PFGE analysis. Interlaboratory reproducibility of pattern and type classification was assessed visually and using gel analysis software. Each typing method showed a different performance level in each center. In the center performing best with each method, inter-IS256 PCR typing achieved R = 100% and D = 100%; 16S-23S rDNA PCR, R = 100% and D = 82%; and MP3 PCR, R = 80% and D = 83%. Concordance between rep-PCR type and PFGE type ranged by center: 70 to 90% for inter-IS256 PCR, 44 to 57% for 16S-23S rDNA PCR, and 53 to 54% for MP3 PCR analysis. In conclusion, the performance of inter-IS256 PCR typing was similar to that of PFGE analysis in some but not all centers, whereas other rep-PCR protocols showed lower discrimination and intralaboratory reproducibility. None of these assays, however, was sufficiently reproducible for interlaboratory exchange of data.

Bacterial Typing Techniques↗

PubMed2001

Accelerometric assessment of levodopa-induced dyskinesias in Parkinson's disease.

Our objective was to develop parameters for objective ambulatory measurements of levodopa-induced dyskinesias (LID) in patients with Parkinson's disease (PD). Twenty-three PD patients with mild to severe LID were submitted to a standardized protocol of 1-minute recordings during rest, talking, stress, and four activities of daily life (ADL). Patients were simultaneously monitored with portable multi-channel accelerometry (four pairs of bi-axial sensors mounted onto the most affected arm, leg, and at the trunk) and recorded by video. LID severity was assessed with a modified Abnormal Involuntary Movement Scale (m-AIMS). The signals were analyzed, and every 1/8-second interval the amplitude was obtained of the dominant frequency within 1-4 Hz and 4-8 Hz frequency bands (Amp1-4 and Amp4-8). For both measures, convergent validity, reproducibility, and responsiveness were determined. In absence of voluntary movements, a significant relation was found between Amp1-4 and Amp4-8 and m-AIMS. Repeated measurements during rest showed a high reproducibility (intraclass correlation coefficient = 0.90 [Amp1-4] and 0.86 [Amp4-8]). The extent to which LID increased with talking and stress correlated significantly (p = 0.02) between the objective and clinical measures (intraclass correlation for differences = 0.67). During ADL, LID occurred in a similar frequency band as voluntary movements and only Amp1-4 and Amp4-8 of the trunk and leg sensor remained highly correlated with m-AIMS. Although objective measures of LID are reliable and responsive, they fail to distinguish LID from voluntary movements. These measures are of value only when obtained during rest (all sensor sites) or during ADL when derived from those body segments that are normally not involved in these ADL tasks (trunk and leg).

Acceleration↗

PubMed1980

Reproducibility of serological titers.

Serologists are making increasing use of the term "reproducibility" when referring to the reliability or repeatability of serological tests. The practical use of the concept, however, has been limited by the absence of an appropriate numerical scale on which differing reproducibilities can be quantified and objectively compared. This limitation can be overcome by adopting the proposed quantitative measure of reproducibility. The recommended measure is a natural extension of the common practice of considering a serological test to be acceptably reporducible so long as replicate titers remain within a twofold range. The measure can be readily used in the field of serology, and examples are given of how this can be done.

Antibodies, Viral↗

PubMed2005

Vapor-phase analysis of isobutyl acetate, isopropyl acetate, n-propyl acetate and their respective alcohols using solid-phase microextraction-gas chromatography with a mass selective detector.

A solid-phase microextraction (SPME)-GC-MS method for three esters and the corresponding alcohols was tested for responses in accuracy, within-run precision (repeatability), and between-run precision (reproducibility) due to individual operators, individual analysis days, and differing analyte concentrations. At 5 ppm (v/v) [ppmv], three of the six analytes showed significant (p < 0.05) operator effects, while five of six analytes gave a significant effect due to the days of analysis. At 20 ppmv, five of the six analytes gave significant operator and daily effects. At 100 ppmv, all the analytes showed significant daily effects but no operator effects were observed. The repeatability was concentration dependent, with all six analytes combining for an average RSD of 12.1 +/- 6.1% at 1 ppmv, becoming most precise at 50 ppmv at 1.01 +/- 0.45%, then increasing at 100 ppmv to 4.12 +/- 1.88%. The contributors to error trended as: concentration > daily effects > operator.

2-Propanol↗

PubMed1996

Methylene blue selectively stains intestinal metaplasia in Barrett's esophagus.

BACKGROUND: Specialized columnar epithelium in Barrett's esophagus resembles gastric intestinal metaplasia, which selectively stains with methylene blue. METHODS: We prospectively evaluated the safety, accuracy, reproducibility, cost, and diagnostic yield of methylene blue-directed biopsy in detecting specialized columnar epithelium and dysplasia in Barrett's esophagus. We performed upper endoscopy with methylene blue-directed biopsy and obtained 236 large cup biopsy specimens (145 stained, 91 unstained) from 14 patients with Barrett's esophagus of any length (Group 1) and 12 control patients. Biopsy specimens were independently examined by two pathologists unaware of the endoscopic results. RESULTS: Methylene blue stained specialized columnar epithelium in 18 of the 26 patients, including those with intramucosal carcinoma (1), high-grade dysplasia (1), and indefinite/low-grade dysplasia (6). Methylene blue staining pattern, which was focal in 72% and diffuse in 28% of patients, was reproduced in 8 patients who had repeat staining within 4 weeks. The overall accuracy of methylene blue staining for detecting specialized columnar epithelium was 95%. The diagnostic yield of methylene blue staining for specialized columnar epithelium in "control" patients was 42%. The risk for dysplasia in stained biopsy specimens was greater than in unstained ones (odds ratio 17.7, p = .0004). CONCLUSIONS: Methylene blue mucosal staining is a safe, inexpensive, reproducible, and highly accurate method of diagnosing specialized columnar epithelium in Barrett's esophagus.

Barrett Esophagus↗

PubMed2003

Reproducibility of natural head position measured with an inclinometer.

Sagittal (pitch) and transversal (roll) natural head position (NHP) was measured once in 20 subjects, 18 to 24 years of age, with an inclinometer; the measurements were repeated 2 years later. The method error (reproducibility) after 2 years was 1.1 degrees for sagittal and transversal measurements. The mean change in NHP measurement was -0.3 degrees for both measurements, and the variance was 1.21 degrees (= 1.1(2)).

Adolescent↗

PubMed1996

Assessment of cardiac performance: short- and medium-term variability of impedance cardiography at rest and during dynamic exercise.

Short- and medium-term variability of impedance cardiography at rest and during exercise at a heart rate of 155-160 beats/min were assessed in 12 healthy men aged 21-28 years. Two consecutive measurements within 1 min were performed 4 times at 2-hour intervals on 2 days 14 days apart. Ejection fraction was the most reproducible of all impedance cardiography parameters, the CV ranging from 3.3-5.9%. The short-term reproducibility of cardiac output and stroke volume at rest was good, the between-repeats coefficient of variation (CV) being 4-6%. The reproducibility weakened with longer time span (between-day CV being about 12%) and higher heart rates (exercise). However, even the between-day reproducibility at rest was as good as that of heart rate. Between-day CV during exercise were about 20%.

Adult↗

PubMed1999

Canine model of ventricular fibrillation using programmed stimuli and localized myocardial warming or cooling.

The purpose of this study was to establish an animal model in which ventricular fibrillation (VF) can be induced reproducibly and defibrillation can be accomplished repeatedly. The left anterior descending artery (LAD) was cannulated and perfused with blood from the carotid artery in eleven open-chest dogs. Electrodes of the internal defibrillator were inserted in the cavities of the left atrium and left ventricle via incisions in the left atrial appendage and left ventricular apex. The perfused blood temperature was modulated to produce regional myocardial warming (42 degrees C) or cooling (28 degrees C). In all dogs, VF was repeatedly induced by the combination of warming and left ventricular extrastimuli and by the combination of cooling and right ventricular extrastimuli. The VF was quickly defibrillated by use of the internal defibrillator. The mechanism of VF was found to be reentry by the analysis of activation sequences. This VF model may be useful when evaluating the efficacy of antiarrhythmic drugs because of the high reproducibility.

Animals↗

PubMedDate not supplied

Digital radiography of interproximal caries: effect of different filters.

The aim of this study was to compare the effect of different image processing modes (filters) on reproducibility and validity of the assessment of interproximal carious lesions on digitized radiographic images. Standardized radiographs of 34 extracted teeth exhibiting interproximal caries were obtained. All radiographs were digitized and using the FRIACOM-software the central depth (CD) of each carious lesion was measured on the unchanged radiographic image and after use of five different filters with 7fold and 18fold magnification. All measurements were repeated after 1 week to estimate reproducibility. Histometric CD assessments provided a gold standard for comparison with the radiographic measurements (validity). Neither reproducibility nor validity of CD measurements were improved by one of the filters. Measurements of dentinal lesions showed a statistically higher variability than those of enamel lesions (p<0.001). 18fold magnification provided more valid CD measurements than 7fold magnification (p<0.001). In this study digital manipulations of radiographic images failed to result in statistically significantly improved reproducibility or validity of CD measurements.

Dental Caries↗