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Results for “Reproducibility”

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At least 433 records · Page 24Linked to original sources

PubMed2002

Highly variable spike trains underlie reproducible sensorimotor responses in the medicinal leech.

The nervous system of the leech is a particularly suitable model to investigate neural coding of sensorimotor responses because it allows both observation of behavior and the simultaneous measurement of a large fraction of its underlying neuronal activity. In this study, we used a combination of multielectrode recordings, videomicroscopy, and computation of the optical flow to investigate the reproducibility of the motor response caused by local mechanical stimulation of the leech skin. We analyzed variability at different levels of processing: mechanosensory neurons, motoneurons, muscle activation, and behavior. Spike trains in mechanosensory neurons were very reproducible, unlike those in motoneurons. The motor response, however, was reproducible because of two distinct biophysical mechanisms. First, leech muscles contract slowly and therefore are poorly sensitive to the jitter of motoneuron spikes. Second, the motor response results from the coactivation of a population of motoneurons firing in a statistically independent way, which reduces the variability of the population firing. These data show that reproducible spike trains are not required to sustain reproducible behaviors and illustrate how the nervous system can cope with unreliable components to produce reliable action.

Action Potentials↗

PubMed2003

X-ray technologists' reproducibility from automated measurements of the medial tibiofemoral joint space width in knee osteoarthritis for a multicenter, multinational clinical trial.

OBJECTIVE: To determine the reproducibility of x-ray technologists, 26 in North America (NA), 24 in Europe (EU), in reliably repositioning patient's osteoarthritic (OA) knees, from computerized measurements of minimum joint space width (JSW) and reproducibility in joint repositioning, during their training for the clinical trial. METHODS: Technologists from 12 NA and 12 EU clinical radiology units received identical training, at one site on each continent, in performing the fluoroscopically assisted semiflexed knee examination and in quality control criteria (QCC) for film acceptance. Subjects recruited were 129 in NA and 70 in EU, with both knees radiographed for some subjects. Each technologist radiographed 5 OA knees and repeated the process on the same knees 2 to 7 days later. Minimum medial JSW was measured at a single center on digitized images with computer software that corrected for radiographic magnification. Technologists' reproducibility in joint repositioning and JSW measurement was determined from the difference between test and retest. RESULTS: In all, only 3/50 technologists failed qualification criteria with a repeat-film JSW difference > 0.50 mm. The mean, standard deviation (SD) of the difference in JSW between test/retest for 146 NA film-pairs of -0.020 (0.16) mm was not statistically different from that in 120 EU film-pairs: -0.001 (0.18) mm. In NA and EU 45% of examinations achieved high quality, i.e., JSW difference between repeat films < 0.1 mm, and 92% achieved excellent to good quality with a difference between repeat films < 0.3 mm. NA and EU technologists' reproducibility was unaffected by subject's sex, age, and degree of JSW loss. Reproducibility in joint reposition for all technologists was excellent. CONCLUSION: Between-continent precision of JSW measurements from all accepted pairs of semiflexed views was excellent to very good and similar to the high technical quality achieved in the authors' original report. The value of training incorporating both test/retest radiographs and film QCC is essential for the high technical quality required for multinational clinical trials.

Adult↗

PubMed2003

Quantitative cholescintigraphy: selection of random dose for CCK-33 and reproducibility of abnormal results.

UNLABELLED: Dynamic cholescintigraphy (DCG) is a valid technique for evaluating gallbladder emptying. Cholecystokinin (CCK) as a slow infusion is recommended as a contraction stimulus. The normal ejection fraction (EF) has been shown to be reproducible, although the reproducibility of abnormal results has not been investigated. The aims of the present study were to standardize the CCK administration method (phase 1), obtain EF normality values (phase 2), and evaluate the reproducibility of abnormal results in patients with clinically suspected gallbladder dysfunction (phase 3). METHODS: Phase 1 included 40 healthy volunteers divided into 4 groups (n = 10) and subjected to intravenous CCK infusion according to 4 different regimens (0.25, 0.30, 0.40, and 0.60 Ivy dog units [IDU]/kg). Phase 2 comprised 33 healthy volunteers for determining DCG normality values, and phase 3 evaluated the reproducibility of abnormal results in 44 patients having clinical manifestations compatible with gallbladder dysfunction and showing an abnormal EF in a previous study. RESULTS: The most effective CCK infusion regimen was 0.40 IDU/kg (3.07 ng/kg) over 20 min, because it afforded the least variability and a high EF. When this regimen was applied to the healthy population, the EF was found to be 74.2% +/- 17.1% (mean +/- SD); the inferior normality limit was estimated to be 40%. Abnormal results were recorded in 77% (95% confidence interval, 62%-89%) of the patients. When the 2 DCG studies of phase 3 were compared, the EF correlation coefficient between them was 0.439 (P = 0.003). CONCLUSION: Slow CCK infusion is the best regimen for stimulating gallbladder contraction; an EF of less than 40% is estimated to represent abnormality. The abnormal results for the EF in patients with clinically suspected gallbladder dysfunction proved to be reproducible.

Adolescent↗

PubMed1992

A comparison of six different ways of expressing the bronchodilating response in asthma and COPD; reproducibility and dependence of prebronchodilator FEV1.

Various indices are used to express the bronchodilating response. It is unclear, however, which index is most informative. The aim of this study was to compare six expressions of the bronchodilating response and to examine: 1) the independence of the prebronchodilator forced expiratory volume in one second (FEV1); and 2) the reproducibility of the bronchodilating response. Bronchodilating responses (increases in FEV1 60 min after salbutamol 400 micrograms and ipratropium bromide 80 micrograms) on six test occasions, during two years, of 183 patients (72 asthma, 111 chronic obstructive pulmonary disease (COPD)) from a large bronchodilator intervention study were used. The dependence of the prebronchodilator FEV1 was investigated both between patients (cross-sectional analysis) and within patients (longitudinal analysis) by means of linear regression analysis. The reproducibility of the bronchodilating response was calculated by means of the coefficients of variation (CVs) of the six bronchodilating responses during two years. The CVs of the six expression indices were compared by analysis of variance (ANOVA). No index was independent of the prebronchodilator FEV1. However, some indices were significantly more dependent on the prebronchodilator lung function and, therefore, less reproducible than others. The "% initial" index (change as a percentage of the prebronchodilator value) was the most dependent on the prebronchodilator lung function and had the worst reproducibility (CV ranged from 50-61%). The "% possible" (change as a percentage of the predicted minus prebronchodilator value) and "% achievable" (change as a percentage of the maximal postbronchodilator minus prebronchodilator value) indices were the least dependent on the prebronchodilator value and had the highest reproducibility (CV ranging from 34-53%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

A reproducible method for producing and quantifying the stages of fracture repair.

Male CD-1 mice, 4 to 6 months of age, were used to establish a reproducible model to study the stages of fracture repair. A custom-designed fracture apparatus was constructed, and trials with it demonstrated its capacity to reliably reproduce a closed fracture of the tibia. Dietary and sleep habits in the treated mice were the same as unfractured control mice. Four stages of fracture repair were documented and the duration of each stage was quantifiable and reproducible. The last stage of fracture repair was completed by 21 days postfracture. The reproducibility of the fracture, the reproducibility of the times and stages of fracture repair, the relatively short time to complete the fracture repair process, and the minimal discomfort which allowed the mice to maintain a normal daily routine, suggest that this is an ideal animal model for studying the fracture repair process.

Animals↗

PubMedDate not supplied

Reproducibility of retinal and optic nerve head perfusion measurements using scanning laser Doppler flowmetry.

BACKGROUND AND OBJECTIVE: To evaluate the reproducibility of full-field perfusion analysis using scanning laser Doppler flowmetry (SLDF) for perfusion measurements of the neuroretinal rim of the optic nerve head and the peripapillary retina in patients with open-angle glaucoma or ocular hypertension, and in normal subjects. PATIENTS AND METHODS: SLDF perfusion measurements of the neuroretinal rim and the peripapillary retina were performed on 20 patients with open-angle glaucoma or ocular hypertension (group G) and 20 normal volunteers (group N). Each subject underwent two independent sessions, 30 minutes apart, each involving 5 high quality images. Intrasession and intersession reproducibility coefficients for flow, volume, and velocity were calculated for a single image and for means of 3 and 5 images using analysis of variance models. flow, the intrasession coefficient of reliability was 0.99 each for the rim, nasal retina, and temporal retina in group G and 0.93, 0.93, and 0.95, respectively, in group N. The intersession coefficient of reliability for flow was 0.99 for the rim, 0.95 for the nasal retina, and 0.87 for the temporal retina in group G and 0.87, 0.82, and 0.80, respectively, in group N. Compared with single image analysis, intrasession and intersession reproducibility were generally better when a mean of 3 images and substantially better when a mean of 5 images was used. CONCLUSION: SLDF full-field perfusion analysis is markedly more reproducible than the original software using 10 x 10 pixel windows. Obtaining mean values for at least 3 images improves the intrasession and intersession reproducibility of this technique.

Aged↗

PubMed2004

Reproducibility of anthropometric measurements in children: a longitudinal study.

The purpose of this study was to establish the reproducibility of a series of anthropometric measures performed twice during one week during a three year period in boys and girls. The subjects of this investigation were 39 children (21 boys and 18 girls), 9-10 year of age at the beginning of the study. Children were measured three times with one year interval. Children were classified by Tanner stage 1-2 during the first measurements, stage 1-3 during the second measurements and stage 1-4 during the third measurements. Body height and weight were measured and BMI calculated. All anthropometric parameters were measured according to the protocol recommended by the International Society for the Advancement of Kinanthropometry (Norton & Olds 1996). Nine skinfolds, 13 girths, eight lengths and eight breadths/lengths were measured. The reproducibility of body height (r = 0.995-0.999), body weight (r = 0.990-0.999) and BMI (r = 0.969-0.999) was very high in boys and girls. The intraclass correlations (ICC), technical errors (TE) and coefficients of variation (CV) were quite different depending on the measurement site of the skinfold thickness. It was surprising that the ICCs were highest and TEs and CVs were lowest during the second year of the measurement. The computed ICC was high, and TE and CV values were quite similar and relatively low in girth, length and breadth/length measurements. It was concluded that the reproducibility of girths, lengths and breadths/lengths in children is very high and the reproducibility of skinfolds is high. Specifically, the reproducibility is very high immediately before puberty in boys and girls.

Anthropometry↗

PubMed2004

Reproducibility of the semiflexed (metatarsophalangeal) radiographic knee position and automated measurements of medial tibiofemoral joint space width in a multicenter clinical trial of knee osteoarthritis.

OBJECTIVE: To determine the baseline and longitudinal consistency in reproducibility of the semiflexed metatarsophalangeal (MTP) position in repeat examinations of patients with knee osteoarthritis (OA) recruited for a multicenter clinical trial that terminated within one year (mean duration 0.81 yr), based on precise measurements both of minimum medial tibiofemoral compartment joint space width (JSW) and of tibial inter-rim distance. METHODS: Two technologists from 8 and one technologist from 14 clinical radiology units had received previous training in performing nonfluoroscopic semiflexed MTP knee examinations and in quality control criteria for film acceptance. Patients (N = 402; F = 269) were recruited from 58 rheumatology sites and referred to 22 centers, or "x-ray hubs," across North America. At baseline and at study exit, both knees were x-rayed twice on the same day. All films had quality control, and accepted films were digitized at the Central Radiographic Facility and transmitted to the Central Analysis Facility for computerized measurement of minimum medial compartment JSW and tibial inter-rim distance. JSW loss was calculated in the placebo group for the study period. RESULTS: The median SD of the difference in JSW between same-day test/retest film pairs was 0.9 mm for 767 baseline film pairs (knees with JSW > 0 mm), and 0.08 mm for 631 exit film pairs. JSW reproducibility was unaffected by subject's sex, age, and degree of JSW loss. Among all x-ray hubs, JSW reproducibility was excellent in 14 (SD < 0.1 mm), good in 6 (0.1 < SD < 0.2 mm), and moderate in 2 hubs (0.2 < SD < 0.3 mm). No statistical difference was found in technologists' ability either in positioning OA knees or in their test/retest reproducibility in repositioning joints at baseline and at study exit. JSW did not alter significantly during the study period. CONCLUSION: The protocol for the semiflexed MTP knee position provides a highly reproducible method for anatomically repositioning the knee and for measuring JSW, necessary for OA clinical trials. It is a simple method that can be employed readily at clinical radiology units, as shown by the similarity in JSW precision between x-ray hubs. The results from this large dataset show that throughout the study precise measurements of JSW were obtained from same-day repeat radiographs, findings that together with previous single-center studies confirm the reliability of this method for clinical trial use.

Arthrography↗

PubMed2004

Reproducibility of proximal and distal transcutaneous oxygen pressure measurements during exercise in stage 2 arterial claudication.

AIM: Although transcutaneous oxygen pressure measurements (tcpO2) are largely used in the investigation of vascular patients, its reproducibility is still debated. Indeed an unpredictable gradient exists between arterial and transcutaneous oxygen pressure. We hypothesised that indices taking into account changes over time and independent of absolute starting values would be more reproducible than other indices. METHODS EXPERIMENTAL DESIGN: comparative test-retest procedure (1 to 13 days between tests). SETTINGS: institutional practice, ambulatory care. PATIENTS AND PARTICIPANTS: 15 subjects with stage 2 claudication. INTERVENTIONS: tcpO2 recordings at rest and at exercise during the 2 treadmill tests. MEASURES: calculation of the Delta-from-rest of oxygen pressure index (limb tcpO2 changes minus chest tcpO2 changes), of the resting - or minimal values attained during exercise - of absolute tcpO2 and of the regional perfusion index (regional perfusion index: ration of limb to chest). RESULTS: Both absolute tcpO2 and regional perfusion index at rest showed low reproducibility. During exercise the best reproducibility was attained through Delta-from-rest of oxygen pressure index calculation. Equations from the linear regression analysis (test 2 versus test 1) were 0.88 x -4.2 (r(2)=0.82) at the buttock level and 0.82 x -3.8 (r(2)=0.80) at the calf level. CONCLUSION: TcpO2 measurement on the calf or buttock during exercise, is a reproducible measurement in patients with vascular claudication, specifically when corrected for exercise-induced systemic pO2 changes trough Delta-from-rest of oxygen pressure calculation.

Aged↗

PubMed2005

Reproducibility and sensitivity to change of 5 methods for scoring hand radiographic damage in patients with rheumatoid arthritis.

OBJECTIVE: To compare intrarater and interrater reproducibility and sensitivity to change of 5 scoring methods for radiographic damage on hand radiographs in patients with rheumatoid arthritis (RA). METHODS: Radiographs of 22 patients from Norway and France with average 2 years' disease duration at baseline and mean 30 months' followup were assessed by 2 readers according to Larsen, Larsen/Rau, Sharp, Sharp/van der Heijde, and Simple Erosion Narrowing Score (SENS) methods. Reproducibility at baseline and on progression was assessed using intraclass correlation coefficients (ICC) and Bland-Altman graphs. Sensitivity to change was compared across methods by computing the country-adjusted standardized response means (SRM) ratio. RESULTS: Intrarater reproducibility varied with the reader (ICC ranging from 0.90 to 0.97), with Larsen and Larsen/Rau ranking highest. Interrater reproducibility was highest with Sharp and Sharp/van der Heijde (ICC 0.76 to 0.93). Bland-Altman graphs showed a decrease of concordance in cases of more severe damage. Sensitivity to change was higher with Sharp and Sharp/van der Heijde modified for erosions (SRM ratio 1.44 and 1.70), than with Larsen/Rau and SENS. The differences between Sharp, Sharp/van der Heijde, and Larsen were less for joint space narrowing. There was a significant reader effect (p < 0.05) in all but the Sharp method. Expressed as percentage of the maximum score, the smallest detectable difference varied between 3.5% (Sharp/van der Heijde) and 14.2% (SENS erosion). CONCLUSION: All methods have high intraobserver and interobserver reliability. The interrater reproducibility decreases with disease severity. Recent modified methods perform best to detect changes, but the advantages of SENS seemed to be lost when applied on hand radiographs alone. Training the readers appears to be essential.

Arthritis, Rheumatoid↗

PubMedDate not supplied

Reproducibility of transpulmonary thermodilution measurements in patients with burn shock and hypothermia.

Thermal noise, including hypothermia and short-term variations in body temperature, has been reported to influence the accuracy and reproducibility of thermodilution measurements. This variation might theoretically limit the usefulness of this technique in patients with acute burns. We therefore sought to determine the reproducibility of hemodynamic parameters derived from arterial thermal dilution in patients with acute burns and hypothermia. This was a prospective, clinical study of 50 mechanically ventilated patients with burns involving more than 25% of the body surface area that were treated at an eight-bed intensive care burn unit in a university-affiliated hospital. A total of 750 arterial thermodilution measurements were analyzed using the COLD system. Triplicate measurements of the intrathoracic blood volume, cardiac output, total blood volume, and extravascular lung water were performed at regular intervals during the first 48 hours after the thermal injury. Reproducibility was assessed by the coefficient of variation of the triplicate measurements. The correlation of variation was less than 10% at all measurement times for cardiac output, intrathoracic blood volume, and total blood volume. For the extravascular lung water, the coefficient of variation ranged from 9.5% to 12.9%. A maximum of 12.9% was found at 48 hours after burn. No correlation was found between body core temperature and the reproducibility of intrathoracic blood volume index (r = 0.145), cardiac index (r = 0.217), or extravascular lung water index (r = 0.167). The parameters derived from arterial thermodilution show a clinically sufficient reproducibility in patients with acute burns associated with thermal instability.

Adolescent↗

PubMed2005

Reproducibility of 3'-deoxy-3'-(18)F-fluorothymidine microPET studies in tumor xenografts in mice.

UNLABELLED: 3'-Deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) has been used to image tumor proliferation in preclinical and clinical studies. Serial microPET studies may be useful for monitoring therapy response or for drug screening; however, the reproducibility of serial scans has not been determined. The purpose of this study was to determine the reproducibility of (18)F-FLT microPET studies. METHODS: C6 rat glioma xenografts were implanted into nude mice (n = 9) and grown to mean diameters of 5-17 mm for approximately 2 wk. A 10-min acquisition was performed on a microPET scanner approximately 1 h after (18)F-FLT (1.9-7.4 MBq [50-200 muCi]) was injected via the tail vein. A second microPET scan was performed approximately 6 h later on the same day after reinjection of (18)F-FLT to assess for reproducibility. Most of the mice were studied twice within the same week (for a total of 17 studies). Images were analyzed by drawing an ellipsoidal region of interest (ROI) around the tumor xenograft activity. Percentage injected dose per gram (%ID/g) values were calculated from the mean activity in the ROIs. Coefficients of variation and differences in %ID/g values between studies from the same day were calculated to determine the reproducibility after subtraction of the estimated residual tumor activity from the first (18)F-FLT injection. RESULTS: The coefficient of variation (mean +/- SD) for %ID/g values between (18)F-FLT microPET scans performed 6 h apart on the same day was 14% +/- 10%. The difference in %ID/g values between scans was -0.06% +/- 1.3%. Serum thymidine levels were mildly correlated with %ID/g values (R(2) = 0.40). Tumor size, mouse body weight, injected dose, and fasting state did not contribute to the variability of the scans; however, consistent scanning parameters were necessary to ensure accurate studies, in particular, controlling body temperature, the time of imaging after injection, and the ROI size. CONCLUSION: (18)F-FLT microPET mouse tumor xenograft studies are reproducible with moderately low variability. Serial studies may be performed to assess for significant changes in therapy response or for preclinical drug development.

Animals↗

PubMed2006

Reproducibility of a task description questionnaire for working pregnant women.

The objective of this study was to evaluate the reproducibility of a Task Description Questionnaire that was designed to investigate exposures to, and influential factors for, problematic tasks experienced by working pregnant women. The questionnaire comprised questions concerning 22 task components (covering working posture, manual material handling, work pace, prolonged postures and others), eight influential factors contributing to problematic tasks, discomfort (measured using a body map) and level of effort to perform the tasks. Reproducibility of the questionnaire was assessed by interviewing participants on two occasions one week apart for interviews at both 20 and 34 weeks of pregnancy. Eleven and 13 problematic tasks were reported by 21 working pregnant women at 20 and 34 weeks of pregnancy, respectively. These tasks were surveyed using the Task Description Questionnaire. Kappa statistics and correlation coefficients (supplemented by paired t-tests) were used to examine the reproducibility of responses to the questionnaire. The results showed that most of the variables were measured with very good or satisfactory reproducibility. The reproducibility of exposure to work posture was higher than that of exposure to manual material handling. There was no significant difference between test and retest means for the discomfort scores measured on the body map, except for the maximum discomfort score for the whole body in the 34 weeks survey. The study suggests that the questionnaire can be reliably used in the study of problematic tasks experienced by pregnant women. But an initial preview of the questions by the subjects and explanation of the questions given to the subjects by the interviewer may help to produce more reliable results.

Female↗

PubMed1989

Reproducibility of iodine-123-hippuran renoscintigraphy in the normal pig at various flow rates.

Twenty-two pigs with normal kidney function and upper urinary tracts were examined with renoscintigraphies once a week for 4 weeks. In order to study the influence of urine flow on the reproducibility, renoscintigraphies were undertaken during various urinary flow rates. Renal split function was reproducible at any level of and independent of the urinary flow rates. For parenchymal and pelvic mean transit times a normogram was constructed for selected urinary flow intervals. An inverse relationship to urine production was seen. Parenchymal and pelvic transit times were fully reproducible when data were compared in two or three consecutive examinations of the same kidney at the same urinary flow rate. Both parenchymal and pelvic mean transit times were however significantly different (p less than 0.001) in kidneys studied from one urinary flow rate to another. Single kidney hippuran clearance was fully reproducible when compared in the same urinary flow interval. However a significant difference was found (p less than 0.05) when single kidney hippuran clearance was compared in renographies undertaken at different urinary flow intervals. Furthermore the study suggests that the size of hippuran clearance is dependent on the urine production, since an increase in hippuran clearance was seen in relation to increase in urinary flow. In conclusion this pig study showed, that monitoring of the urinary flow rate is extremely important in this very commonly used clinical investigation, and that the investigation should be performed in the same state of hydration at any renography to obtain reproducible results.

Animals↗

PubMed1989

[Reproducibility of the Doppler spectrum of the left ventricular stroke volume].

The left ventricular stroke volume was determined in 15 healthy male volunteers of the same age (21-23 yrs). The systolic function was characterized by six, the diastolic function by five parameters. The diameter and the cross-sectional areas of the outflow tract were determined. Intraobserver, interobserver and day-to-day variability of these parameters were investigated. The reproducibility was tested by 4 statistical methods. The significance of the differences between the mean values was determined, as well as the percentual difference of the mean values and of the variation coefficients. Linear regression analysis was done and the correlation coefficient was determined for each parameter. The variation coefficient could be regarded as the best statistical method for characterizing the reproducibility. Thus the simplest, directly measured Doppler parameters gave the best reproducibility. The reproducibility of the complex, calculated parameters was poorer. Comparing the intra- and interobserver reproducibility error, the former one was less.

Adult↗

PubMed1989

Dysplastic melanocytic nevi: a reproducible histologic definition emphasizing cellular morphology.

Histologic criteria commonly used to diagnose dysplastic melanocytic nevi (DMN) have not been correlated adequately with biology nor subjected to rigorous reproducibility studies. To address these failings, we developed histologic definitions emphasizing cellular morphology based on the appearance of typical melanocytes in sun-protected buttock skin, fully-evolved atypia in the vertical component of metastasizing primary cutaneous melanomas, and slight and moderate degrees of atypia defined within these limits in selected varieties of DMN. Reproducibility of our histologic definitions were tested by using two pathologists working independently to assess single routine tissue sections of 19 melanocytic lesions on two occasions at least 6 mo apart. Lesions included five previously diagnosed primary invasive cutaneous melanomas, seven lesions selected for gross morphologic features characteristic of DMN, and four solar lentigines and three common acquired nevomelanocytic nevi preselected for typical appearance and stable growth history. For the primary pathologist using the grading scheme, agreement rates between first and second readings were 84% for final diagnosis and 79% for the highest degree of cellular atypia; for the secondary pathologist, agreement rates for first and second readings for both parameters were 84%. Agreement rates comparing second readings of final diagnosis and highest degree of cellular atypia by the two pathologists were 89% and 79%, respectively. Most of the architectural and host response features commonly associated with DMN were less reproducible. In conclusion, we demonstrated very good reproducibility of histologic definitions used to differentiate the intraepidermal component of DMN from that of melanoma and benign melanocytic and nevomelanocytic hyperplasias, based on a biologic correlation emphasizing cellular morphology. Reproducible histologic definitions are a requisite first step in defining a clinical-pathologic correlation for DMN.

Adolescent↗

PubMed1994

Increase in blood pressure reproducibility by repeated semi-automatic blood pressure measurements in the clinic environment.

OBJECTIVE: To evaluate whether increasing the number of blood pressure readings obtained in the clinic environment increases the blood pressure reproducibility. PATIENTS: Thirteen mild essential hypertensive patients studied in the outpatient clinics, following withdrawal of antihypertensive treatment for 4 weeks. METHODS: The systolic and diastolic blood pressures were measured three times, using a mercury sphygmomanometer, with the patient in the sitting position. Measurements were then performed with the patient in the lying position using an oscillometric device (SpaceLabs 90202 or 90207). The device was operated semi-automatically at 3-min intervals until 25 readings had been collected. The same procedure was repeated 4 weeks later. The systolic blood pressure, diastolic blood pressure and heart rate were averaged by considering a progressively greater number of readings, from 1 to 25. The reciprocal of the standard deviation (1/SD) of the mean difference after 4 weeks was taken as the measure of reproducibility. RESULTS: 1/SD increased progressively as the number of semi-automatic blood pressure readings from which the average was calculated increased. For a similar number of blood pressure readings the reproducibility was similar for semi-automatic readings to that for automatic readings obtained by 24-h ambulatory blood pressure monitoring. CONCLUSION: Multiple blood pressure readings obtained semi-automatically in the outpatient clinics increase blood pressure reproducibility and make the value similar to that obtained by ambulatory blood pressure monitoring. The advantage of an increase in reproducibility for studies on antihypertensive drugs thus depends on the number of readings, and can also be obtained by semi-automatic measurements in the clinic environment.

Adult↗

PubMed1993

Long-term reproducibility of individual indices of time-domain analysis, spectral temporal mapping, and spectral turbulence analysis of signal-averaged ECGs.

This study compared short-term (1 day) and long-term (1 week and 1 month) reproducibility of the numerical results of 21 individual indices of time-domain analysis, spectral temporal mapping, and spectral turbulence analysis of the signal-averaged electrocardiogram in 28 healthy volunteers (18 men, 10 women, mean age, 31 years; range, 22-39 years). For each of the 21 indices and for each of the repeated recordings (ie, recordings on day 1, 7, and 30), the mean relative error versus recording of day 0 was calculated together with the rank correlation coefficient. The study showed that (1) reproducibility of time-domain analysis with the 40-Hz high-pass filter was superior to that of time-domain analysis performed with the 25-Hz high-pass filter, (2) reproducibility of time-domain variables was similar to that of spectral turbulence analysis of the entire QRS complex and was superior to that of spectral temporal mapping, (3) reproducibility of frequency-domain techniques not based on time-domain measurements (such as spectral turbulence analysis of the entire QRS complex) was significantly better than that of frequency-domain techniques combined with time-domain measurements (such as spectral turbulence analysis of the low-power terminal QRS region or spectral temporal mapping), and (4) short- and long-term reproducibility of signal-averaged electrocardiographic indices is similar in a healthy population.

Adult↗