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At least 811 records · Page 45Linked to original sources

PubMed1991

Reproducibility of image interpretation in immunoscintigraphy performed with indium-111- and iodine-131-labeled OC125 F(ab')2 antibody injected into the same patients.

An important criterion for the clinical use of a new imaging technique is the correct reproducibility of interpretation. Forty-six paired immunoscintigraphic examinations were performed on 43 patients with suspected ovarian carcinoma recurrence using F(ab')2 fragments of OC125 antibody labeled first with indium-111 and then with iodine-131. Planar scintigraphy (PS) and emission computed tomography (ECT) images were interpreted blindly and separately by three observers, and reproducibility was evaluated by a kappa concordance index. Intra- and interobserver reproducibility were generally satisfactory (kappa values of 0.6 and 0.7, respectively). Binomial analysis of kappa values for ECT showed the superiority of indium-111 for intraobserver (p = 0.035) and interobserver (p = 0.0039) study. However, for PS there was no significant difference in reproducibility with the two radionuclides.

Adult↗

PubMed1990

Reproducibility of ambulatory blood pressure load.

Twenty-two hypertensive patients were monitored during two separate drug-free occasions with a Del Mar Avionics ambulatory device. Blood pressure loads (percentage of systolic and diastolic readings more than 140 and 90 mmHg, respectively) and mean BP were measured both to determine their reproducibility and to examine how they correlate with each other. The systolic and diastolic mean awake BPs for day 1 and day 2 were 140/93 mmHg and 140/91 mmHg, respectively, and BP loads were 45%/55% and 43%/54%. Moreover, mean BP loads correlated highly (r = 0.93) with mean BP values taken on the same day. Both ambulatory mean SBP and BP load were highly reproducible (r = 0.87 and 0.80, respectively, during the awake hours), and mean DBP and load were fairly reproducible (r = 0.59 and 0.39, respectively, during the awake hours). Clinically, however, both were consistent from day 1 to day 2. Mean and individual standard deviations also were reproducible for both systolic and diastolic pressures and loads.

Adult↗

PubMed1989

[Intrarenal kinetics of Gd-DOTA in sequential MRI in rabbits. Reproducibility study].

Ten normal rabbits and seven rabbits with experimental acute renal failure by tubular necrosis were studied with dynamic MR to evaluate the reproducibility of intrarenal kinetics of Gd-DOTA. Sequential spin-echo sequences with short TR (200 msec)/TE (26 msec) were used yielding a 29 sec acquisition time. A usual semi-quantitative analysis of intrarenal contrast demonstrated the reproducibility of some phases of the dynamic sequence in particular a drop in the signal within inner medulla between the third and the fourth minute after infusion. This effect, related to a high concentration of Gd-DOTA within the tubules was observed in 9 over 10 normal rabbits and in none of the rabbits with acute renal failure. The quantitative analysis calculation was based on relative signal intensity and contrast-to-noise ratio from the absolute signal intensity measure on regions-of-interest (ROI) on the cortex, outer medulla and inner medulla. No reproducibility of the variations with time of these parameters could be assessed. A great number of factors of variations or error, mainly during the measurements of signal intensity with ROI, could explain this lack of reproducibility. At the present, dynamic MR is therefore not able to quantitatively evaluate the renal function. Only a semi-quantitative estimation of tubular concentration can be deduced.

Acute Kidney Injury↗

PubMed1994

Microalbuminuria in elderly hypertensives: reproducibility and relation to clinic and ambulatory blood pressure.

OBJECTIVE: To examine the short-term reproducibility of urinary albumin measurements and the relation of urinary albumin excretion to the clinic and ambulatory blood pressure levels in elderly untreated hypertensive subjects. SETTING: Outpatient hypertension clinic of a District General Hospital. MAIN OUTCOME MEASURES: The within-patient reproducibility of 24-h urinary microalbumin and electrolyte excretion and relation to 24-h and clinic blood pressure levels. PATIENTS: Sixty-four untreated elderly hypertensives (mean age 74.7 years, range 64-82) with systolic blood pressure > or = 160 mmHg or diastolic blood pressure > or = 95 mmHg, or both, were recruited from general practitioner clinics and current outpatient attenders. The patients had not received antihypertensive treatment for at least 4 weeks. METHODS: The clinic and 24-h non-invasive ambulatory blood pressures were recorded with a simultaneous 24-h urine collection for measurement of the urinary albumin and electrolyte excretion. Thirty-seven subjects performed two consecutive 24-h urine collections for an assessment of the short-term reproducibility of the albumin and electrolyte excretion. RESULTS: The coefficient of variation of 24-h urinary albumin excretion was 62%, and for the albumin:creatinine ratio 52%, compared with 19% for sodium and 15% for potassium excretion. The urinary albumin excretion correlated with clinic systolic blood pressure (r = 0.33, P = 0.01) and with 24-h ambulatory systolic (r = 0.48, P < 0.001) and diastolic (r = 0.32, P = 0.01) blood pressure. The subjects with microalbuminuria (24-h urinary albumin excretion in the range 30-300 mg) had higher clinic and ambulatory blood pressures than those with lower levels of albumin excretion. CONCLUSIONS: The low day-to-day intrasubject reproducibility in the 24-h urinary albumin excretion considerably reduces the potential value of single collections in the assessment of microalbuminuria in elderly hypertensives. The urinary albumin excretion correlates with the clinic and 24-h ambulatory blood pressures in elderly hypertensives.

Aged↗

PubMed1993

[Reproducibility of the nyctohemeral cycle of blood pressure in patients with severe Parkinson disease].

UNLABELLED: Nineteen hospitalised, severe and treated parkinsonians (9 males, 10 females), stage IV and V of Hoehn and Yahr's classification, underwent 2 days running ambulatory blood pressure monitoring (ABPM) by ABPM 630 Nippon-Colin device, during a period of therapeutic stability. Hospitalisation allowed reproducibility of daily activity. Diurnal, nocturnal and 24 hours systolic blood pressure (SBP), as well as nocturnal and 24 hours diastolic blood pressure (DBP) were reproducible with a good correlation for each patient. Diurnal diastolic BP was the lone not reproducible value but had a good day 1-day 2 correlation. [table: see text] CONCLUSION: Parkinsonian ABPM data, except diurnal DBP, are reproducible.

Adult↗

PubMed1994

Reproducibility of the NEI Scheimpflug Cataract Imaging System.

PURPOSE: The NEI Scheimpflug Cataract Imaging System was developed to allow for easy, accurate and reproducible image analysis of nuclear cataracts. This study was undertaken to determine the reproducibility of densitometric measurements of the lens nucleus using this modified system. METHODS: Replicate Zeiss Scheimpflug images of the lenses in 143 eyes were obtained by one photographer. Normal and cataractous lenses (without central cortical or anterior subcapsular opacities) were sampled. Images were stored after testing for adequacy using immediate exposure checking. Densitometry of the nuclear region was then performed for each image. The interval within which 99% of the differences between repeat measurements may be expected to lie was used as a measure of reproducibility (99% range). RESULTS: A 99% range of +/- 0.023 optical density units (odu) was obtained for nuclear densities < 0.30 odu (125 eyes). For lenses with nuclear densities > or = 0.30 odu (18 eyes), the 99% range was +/- 0.14 times the first measurement. CONCLUSION: This study shows the excellent reproducibility of this Scheimpflug imaging system in the nuclear region and demonstrates its usefulness in studies on nuclear cataracts, particularly for natural history studies and clinical trials of anti-cataract drugs.

Cataract↗

PubMed1993

Reproducibility of quantitative arteriographic assessment of atherosclerosis in the femoral artery.

Results from computer-analysed angiograms in the Probucol Quantitative Regression Swedish Trial (PQRST) were analysed to determine the reproducibility of the method and any drift in the analysing system. The precision index (P(mu)) for 2 angiography series, made at 10 min intervals, of the femoral artery in 276 patients was 10.5 for lumen volume and 21.9 for roughness (edge irregularity). No difference in reproducibility was found between patients with and without symptoms of peripheral atherosclerosis or when looking at the reproducibility over years. A drift of 0.67% per year in the radiographic equipment (but not in the analysis system) was found, confirmed by use of phantoms. Computer-based analysis of femoral atherosclerosis is a reliable method for follow-up trials, giving high reproducibility even if the trial spans over several years and involves different centres. The use of phantoms is essential for checking the method over time.

Adult↗

PubMed1993

Discrimination and reproducibility of an information maximizing multivariable model.

Predictor variables for multivariate rules are frequently selected by methods that maximize likelihood rather than information. We compared the discrimination and reproducibility of a prediction rule for pneumonia derived using extended dependency analysis (EDA), an information maximizing variable selection program, with that of a validated rule derived using logistic regression. Discrimination was measured by receiver-operating characteristic (ROC) analysis, and reproducibility by rederivation of the rule on 200 replicate samples of size 250 and 500, generated from a training cohort of 905 patients using Monte Carlo techniques. Four of the five predictor variables selected by EDA were identical to those selected by logistic regression. With each variable weighted by its conditional contribution to total information transmission, EDA discriminated pneumonia and nonpneumonia in the training cohort with an ROC area of 0.800 (vs 0.816 for logistic regression, p = 0.60), and in the validation cohort with an area of 0.822 (vs 0.821 for logistic regression, p = 0.98). EDA demonstrated reproducibility comparable to that of logistic regression according to most criteria for replicability. Replicate EDA models showed good discrimination in the training and testing cohorts, and met statistical criteria for validation (no significant difference in ROC areas at a one-tailed alpha level of 0.05) in 80.8% to 94.2% of cases. We conclude that extended dependency analysis selected the most important variables for predicting pneumonia, based on a validated logistic regression model. The information-theoretic model showed good discriminatory power, and demonstrated reproducibility according to clinically reasonable criteria. Information-theoretic variable selection by extended dependency analysis appears to be a reasonable basis for developing clinical prediction rules.

Cohort Studies↗

PubMed1993

[Reproducibility of heart rate variability measurements in repeated 24-hour long-term ECG registration].

Heart rate variability (HRV) is considered to indicate cardiac autonomic reflex activity. The reproducibility of HRV determinations from repeated Holter recordings has not been vigorously evaluated. This represents, however, an important question since HRV determinations are increasingly used to examine disease-related changes in the autonomic tone or the effects of therapeutic interventions. Thus, the present study examined the reproducibility of 4 commonly used time-domain parameters (SDNN, SDANN, rMSSD, pNN50) and the spectral components of HRV in 17 healthy volunteers and in patients with coronary artery disease (n = 9) or hypertensive heart disease (n = 9). In all subjects, 2 Holter recordings were obtained 7 days apart. In both, healthy volunteers and in patients, overall reproducibility of HRV parameters was good exhibiting correlation coefficients between 0.60 and 0.98. However, in individual subjects particularly in those without heart disease a higher degree of variability of HRV measurements was observed. In those patients with markedly reduced HRV, reproducibility was best. It is concluded that repeated HRV determinations may be utilized to examine the effects of underlying disease progress or of therapeutic interventions on cardiac autonomic tone.

Adult↗

PubMed1993

Reproducibility of ambulatory blood pressure and assessing treatment withdrawal in hypertension trial.

Ambulatory blood pressure monitoring (ABPM), like casual blood pressure (BP), is imperfectly reproducible between visits. The reproducibility of ABPM is less than the reproducibility predicted from a simple model of random variation of BP. This suggests either increased technical error in the technique, an element of increased biologic variability, or both. In addition, ABP shows a between-day variation (add about 6 to 7 mm Hg diastolic, similar in magnitude to what is observed with casual BP) which cannot be obviated by the average of many within-day measurements. The reliability of ABPM, although conventionally judged excellent at about RI = 0.75, is insufficient to avoid misclassification errors and regression to the mean when BP cutpoints are employed. About 40% of patients apparently failing treatment withdrawal at a threshold of +2 SD, or about 95 mm Hg diastolic ABP, will be false-positive failures when categorized by a single ABP. Despite the inconvenience, obtaining an average of two or more ABP measurements on different days may be cost-saving to a clinical trial because of the improved reproducibility; other costs may exceed $1000 per entrant.

Ambulatory Care↗

PubMed1995

[Reproducibility of echocardiographic parameters by automatic detection of contours in hypertensive patients].

The reproducibility of automatic outline detection is a echocardiographic reproducibility which has been poorly evaluated in patients with cardiomyopathy. Two independent observers identified the systolic surface and mid and end diastolic surfaces of 27 hypertensive patients, who had been referred to the laboratory for the measurement of left ventricular mass. Each observer examined on two occasions all parameters and all parameters were measured at least 2 hours apart. The coefficient of variation (CV) expresses the reproducibility of each measurement. The intra observer was 10 to 15% and the inter observer 15 to 22% for the measurement of surface area. The coefficient of variation is regularly greater than 20% for measures of maximum speed, which characterise surface changes in diastole. The automatic detection of contours is a echocardiographic tool whose potential is great for evaluating left ventricular function but the current versions can only be applied to very selective group of patients depending on the quality of their echographic window for acoustic quantitation. This technique is very operator dependent, in particular as regards setting the gains and this explains its poor reproducibility and its limited interest in daily clinical practice.

Adult↗

PubMed1996

[Reproducibility of signal-averaged electrocardiography].

The reproducibility of the parameters defining the presence of late potentials on the signal-averaged electrocardiogram is one of the limiting factors of the method. The authors studied the coefficients of correlation and reproducibility of these parameters in patients with coronary artery disease. In addition, they tried to determine which parameter was most often responsible for changing a diagnostic conclusion (i.e., presence or absence of late potentials). Two signal-averaged ECGs were recorded one after the other in 127 patients. The presence of late potentials was defined as the presence of a least two of the following criteria: total amplified and averaged QRS duration (tQRS) > 114 ms: duration of the last signal of under 40 microV (LAS) > 38 ms, and root mean square of the amplitude of the last 40 ms (RMS) < 20 microV. The correlation coefficients were 0.98, 0.96 and 0.94 for the duration of tQRS, LAS and RMS respectively (p < 0.0001). The coefficients of reproducibility were 7.0 ms. 7.0 ms and 16.1 microV respectively. Late potentials were present in 22% of patients. A change in diagnosis between the first and second recording was observed in 10 subjects (8% of the population). A combined change in LAS and RMS was responsible for 6 of these revised diagnoses, a change in LAS alone in 2 cases, of the RMS alone in 1 case and the tQRS alone in 1 case. In patients with coronary artery disease, the immediate reproducibility of the diagnosis of late potentials is affected by changes in LAS and RMS. The tQRS is only rarely responsible for a change in diagnosis. This study suggests that the result of the signal-averaged ECG should be interpreted with caution when the LAS or RMS are near their threshold values.

Action Potentials↗

PubMed1996

[Influence of the duration of recording in the reproducibility of the signal averaged electrocardiogram].

The authors studied the possibility of improving the reproducibility of the signal averaged ECG by increasing the number of averaged QRS complexes. One hundred patients were included in the study. In each cases, 400 QRS complexes were recorded on twice, consecutively, in strictly identical conditions. During each recording, the total duration of the amplified and averaged QRS complex (tQRS), the duration of the terminal signal below 40 microV (LAS) and the root mean square of the amplitude of the last 40 ms (RMS) were determined for 100, 200, 300 and 400 recorded QRS complexes. The presence of late potentials was defined as the positivity of two of the following criteria: tQRS > 114 ms, LAS > 38 ms, RMS < 20 microV. The number of contradictory diagnostic conclusions between two successive recordings of the same duration decreased progressively with the number of averaged QRS complexes: 10 for 100 QRS, 10 for 200 QRS, 9 for 300 QRS and 6 for 400 QRS complexes, but this improvement was not statistically significant. The absolute differences of tQRS and RMS between two successive recordings of the same duration were statistically different for the four durations of recording (p = 0.05) and there was a tendency towards statistical significance for LAS (p = 0.09). The best quantitative reproducibility of the 3 parameters was obtained with the recording of 300 QRS complexes. In conclusion, the reproducibility of the signal averaged ECG is improved when the number of average QRS complexes is increased. The authors' results suggests that reproducibility this is optimal with the amplification and averaging of 300 QRS complexes.

Action Potentials↗

PubMedDate not supplied

Long term reproducibility of ambulatory blood pressure monitoring.

The long term reproducibility of ambulatory blood pressure measurements was evaluated over two 24 h recordings made under identical conditions 2 years apart in 20 normotensive and 13 essential hypertensive patients not receiving antihypertensive treatment. There was excellent agreement between the mean 24 h values of blood pressure as well as for the day time and night time means. The standard deviation of the differences was half that of casual determinations. On the other hand, the reproducibility of the mean hourly values was comparable to that of casual measurements. The reproducibility of the white coat effect was poor, as assessed by the difference between blood pressure on fitting the device and the mean day time value. These results indicate that the short term reproducibility of ambulatory blood pressure is maintained over the long term.

Blood Pressure Monitoring, Ambulatory↗

PubMed1996

Reproducibility of measurements of regional resting and hyperemic myocardial blood flow assessed with PET.

UNLABELLED: PET with 13N-ammonia permits the noninvasive quantification of myocardial blood flow (MBF) in humans. The present study was done to assess the reproducibility of quantitative blood flow measurements at rest and during pharmacologically induced hyperemia in healthy individuals. METHODS: Thirty healthy volunteers (26 men, 4 women) were studied. Paired measurements of MBF at rest (n = 21), during adenosine (n = 15) and during dipyridamole (n = 7) were performed using a two-compartment model for 13N-ammonia PET. The mean difference between baseline and follow-up blood flow (% difference) was calculated to assess reproducibility. RESULTS: No significant difference was observed between resting blood flow at baseline or follow-up (15.8% +/- 15.8%; p = ns). Baseline and follow-up resting blood flow were linearly correlated (r = 0.63, p < 0.005). Normalization of resting blood flow to the rate pressure product improved the reproducibility significantly (15.8% +/- 15.8% versus 10.1% +/- 10.5%, p < 0.05). Baseline and follow-up hyperemic myocardial blood flow did not differ (11.8% +/- 9.4%; p = ns) and were linearly correlated (r = 0.69, p < 0.0005). CONCLUSION: MBF at rest can be measured reproducibly with 13N-ammonia PET. The individual response to pharmacologic stress appears to be relatively consistent. Thus, serial blood flow measurements with 13N-ammonia PET can be used to quantify the effect of various interventions on MBF and vasodilatory reserve.

Adenosine↗

PubMed1996

[Reproducibility of densitometric examinations of the tibial shaft].

The aim of this paper is to evaluate the reproducibility of tibial shaft densitometry in own method under development. It will be expressed as percentage value of coefficient of variability (%CV). Bone mineral content (BMC) and bone mineral density (BMD) were measured with a dual energy X-ray densitometer Lunar DPX; the data were analyzed with a "Orthopedic" software. Three tibial bone scans were done in 10 males. High reproducibility was found, ranging from 0.98% to 1.45% and from 1.45% to 2.08% for BMC and BMD respectively. Reproducibility increases as the analyzed surface increases. Reproducibility so high allows for further investigations; it might be interesting to monitor BMC and BMD of the tibia in course of fracture treatment by Polfix or Zespol method.

Absorptiometry, Photon↗

PubMed1997

Utility and reproducibility of semiquantitative analysis of sestamibi breast images.

UNLABELLED: Technetium-99m-sestamibi scintimammography has been shown to be a useful diagnostic test in the detection of breast cancer. The purpose of this study was two-fold to: (a) evaluate semiquantitative indices of tracer uptake in lesions and determine if they are helpful in distinguishing benign from malignant breast lesions; and (b) test the reproducibility of these measures of sestamibi uptake in breast images. METHODS: Prone lateral planar imaging was performed on 27 patients after intravenous injection of 20-30 mCi 99mTc-sestamibi. Data were analyzed by creating three regions of interest (ROIs) over designated areas: lesion, normal breast and right chest wall. Lesion-to-normal (L:N) and lesion-to-chest wall (L:CW) ratios were calculated for each patient. Reproducibility was assessed by having two independent observers draw ROIs (interobserver) and one observer draw two independent sets of ROIs (intraobserver). RESULTS: L:N and L:CW ratios were significantly different for malignant versus benign lesions (p < 0.001 for both ratios). Intraobserver and interobserver reproducibility showed good correlation with r = 0.98 (L:CW ratio). CONCLUSION: Semiquantitative analysis of sestamibi breast imaging results in reproducible uptake ratios that may be helpful in objectively interpreting imaging results.

Adult↗

PubMed1997

Improved reproducibility of measurements with the nerve fiber analyzer.

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

Humans↗