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Results for “Repeatability and Reproducibility”

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PubMed1991

[Problems of the reproducibility of the inhaled dosage exemplified with the Pari provocation test I apparatus].

The unspecific bronchial provocation test--usually performed with histamine, metacholine or carbachol--is used to determine whether bronchial hyperreactivity is present, and to what degree. Epidemiological studies have shown, that an overlap exists between "healthy" and "sick". There are several reasons for this, the most important being the insufficient reproducibility of intrabronchial deposition and the fact that the total provocation dose is often unknown. The following factors must be taken into account to improve this situation: 1. Only those devices where the particle spectrum is not influenced by the inspiration flow (without additional airstream) should be used to produce aerosols. 2. The air current containing aerosols is vapour saturated when liquid aerosols are produced. As the vapour is derived from the nebulizing solution it forms part of the weight or volume loss, this can be up to 50% of the total weight/volume loss. The aerosol output is far more constant and practically independent of the vapour saturation and the temperature. The intrabronchial dose can therefore not be calculated according to the weight loss of the nebulizer, as this is incorrect. 3. The evaporation of the nebulizing solution leads to an increase in the concentration of the test substance, especially towards the end of the evaporation process. Thus, the volume of the nebulizing solution should always be as large as possible or renewed early. 4. The slower the inhalation maneuver, the less the reproducibility of the intrabronchial deposition is impaired. The intrabronchial deposition varies least, when a slow inspiratory vital capacity maneuver is carried out (inspiration time greater than 8 s). Exhalation should be normal or even rapid, as aerosol deposition is thus increased, due to airway collapse. Breath-holding at the end of inspiration, for about 3-4 seconds, is favourable. 5. The anatomy of the glottic region varies greatly interindividually, influencing intrabronchial deposition. To reduce this to a minimum, the average diameter of the particles should not exceed 2 microns. On the other hand, the diameter of particles should not be under 1 micron, as the inhaled amount of substance is then markedly reduced (volume approximately d3). 6. Reservoirs, storaging the aerosol before inhalation, increase reproducibility, since they stabilize the aerosol due to vapour saturation. Plastic reservoirs must either be of antistatic material, or made antistatic by being filled repeatedly. The reproducibility of intrabronchial deposition is in the range of +/- 15% for the PARI-Provokationstest device I, (determined by radioactive labelling).(ABSTRACT TRUNCATED AT 400 WORDS)

Aerosols↗

PubMed2002

The Ocular Hypertension Treatment Study: reproducibility of cup/disk ratio measurements over time at an optic disc reading center.

PURPOSE: To determine the reproducibility over time of visual estimates of the horizontal cup/disk ratio by trained technicians from optic disk stereophotographs. METHODS: Baseline optic disk stereophotographs are graded at entry and regraded annually in a masked fashion. The 1,636 participants in the Ocular Hypertension Treatment Study (OHTS) undergo stereoscopic optic disk photography at study entry and annually thereafter. Stereophotographs are graded independently by two technicians at the Optic Disc Reading Center. If the readers' estimates of horizontal cup/disk ratio differ by more than 0.2 disk diameters (DD), they attempt to reach a consensus; if they cannot, the horizontal cup/disk ratio is adjudicated by a glaucoma specialist. RESULTS: The percent of regradings differing by 0.2 DD or more from the estimate of horizontal cup/disk ratio made at entry was 4%, 6%, and 7%, respectively at years 1, 2, and 3. The percent differing by more than 0.2 DD was 1% or less at all years. Intraclass correlation coefficients were 0.93, 0.92, and 0.92, respectively. Estimates of horizontal cup/disk ratio from sequential full-frame photographs and simultaneous split-frame photographs appeared comparable and equally reproducible. Gradings by technicians were comparable to gradings by glaucoma specialists. CONCLUSIONS: High reproducibility between repeated gradings of baseline horizontal cup/disk ratio was achieved by trained technicians adhering to a rigorous protocol. Horizontal cup/disk ratio measurements in OHTS are sufficiently reproducible to provide information about the relationship of cup/disk ratio to the prognosis of individuals with ocular hypertension.

Certification↗

PubMed2002

Loss of heterozygosity and PCR artifacts in a microsatellite analysis of psoriasis and colorectal cancer.

Although a loss of heterozygosity (LOH) is commonly observed using microsatellite markers in a cell-proliferating malignant disorder, controversial findings of psoriasis, a keratinocyte-outgrowth disease, remain to be explained. It was hypothesized that unstable natures of the microsatellite markers for the polymerase chain reaction (PCR) might give a rise to either a false-positive or -negative LOH. Twenty-one frozen skin tissues and 33 formalin-fixed paraffin-embedded archives were obtained from patients with psoriatic plaques and colorectal cancers, respectively. In the frozen psoriatic skin, two of the 17 microsatellite markers selected from 11 chromosomal arms were associated with artifact LOHs that were not reproduced in repeated PCRs. The remaining 15 stable microsatellite markers with few PCR artifacts demonstrated a borderline-level LOH in cases with an ambiguous heterozygosity such as a juxtaposed allelic band. Infrequent LOHs (3 out of 242 heterozygous markers, 1.2%) were detected in psoriatic cases with two separate alleles. In colorectal cancers, a set of the 15 stable microsatellite markers identified a minimal borderline-level LOH at the cut-off point that was same with that of psoriasis. These results indicate that the selection of reproducible microsatellite sequences and the cautious criteria for informative heterozygosity are required to obtain the reliable LOH results from variable genomic DNAs, and that psoriatic lesions harbor few LOH.

Alleles↗

PubMed1991

[Validation of an ultrasonographic method of gastric emptying measurement in men].

Our purpose was to validate an ultrasonographic technique based on the assessment of the gastric antrum. Sixteen patients presenting with various functional disorders were studied by ultrasound on two occasions. Ten healthy volunteers were simultaneously studied by scinti- and ultrasonic scans. After an overnight fast, the healthy subjects ingested a 2,000 kJ test meal containing 150 microCi of 111In DTPA in 250 ml orange juice and 3 mCi of 99m Tc sulfur colloid in chicken liver. Using an ultrasound scanner fitted with a 3.5 MHz transducer, the area of the gastric antrum section was always measured in the same plane. Ultrasonographic measurement of gastric emptying rate was feasible in all of the 10 healthy subjects and in 14 of 16 selected patients. The ultrasonographic method was reproducible, and repeated t 1/2 measurements in 14 patients correlated well (95.3 +/- 27.9 vs 99.2 +/- 20.6 min; r = 0.70, P less than 0.001). The t 1/2 measurement was 39.4 +/- 7.7 min with the ultrasonographic method, and correlated well with 36.4 +/- 4.3 min for the t 1/2 measurement of the liquid phase with the scintigraphic method. We conclude that the ultrasonic method was reproducible and could be used for assessment of gastric emptying rate when repeated measurements are necessary, especially in pharmacologic studies.

Adult↗

PubMed1994

Study of reproducibility of spin trapping results in the use of C-phenyl-N-tert-butyl nitrone (PBN) for trichloromethyl radical detection in CCl4 metabolism by rat liver microsomal dispersions. Biological spin trapping I.

The well-known metabolism of CCl4 to trichloromethyl radicals in rat liver microsomal dispersions has been reinvestigated with the goal to determine the repeatability and reproducibility of the EPR signal intensity of the EPR spectrum of the CCl3 adduct of PBN. It was found that at least eight repeat experiments were needed under identical conditions to obtain an average value with an error of +/- 10%. When the effect of changing the concentrations of CCl4, PBN or NADPH-generating system was investigated, the plots of EPR signal intensity vs. the variable selected showed initial smooth increases in signal strength with respect to an increase in concentrations of CCl4, PBN or NADPH-generating system. However, considerable scatter was found after the initial slope and only general trends could be recognized. It is concluded that with CCl4, no increase in EPR signal is found after 10 mM concentration. For PBN, the optimum concentration is about 30 mM. The signal strength seems to increase with increased amounts of NADPH generating system although with diminishing slope.

Animals↗

PubMedDate not supplied

Solvent-efficient thin-layer chromatographic method for the determination of aflatoxins B1, B2, G1, and G2 in corn and peanut products: collaborative study.

An interlaboratory study of a solvent-efficient thin-layer chromatographic (TLC) method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, France, Tunisia, and Denmark. Eighteen artificially contaminated samples plus blanks of raw peanuts and peanut butter and corn containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The method consists of elements of the U.S. Food and Drug Administration (FDA), Contaminants Branch (CB) (AOAC Method 968.22) and FDA, Best Foods (BF) (AOAC Method 970.45) methods with reduced requirements for solvents. Participating laboratories used either visual or densitometric techniques during the final determinative step. Statistical analysis of the data was performed to determine or confirm outliers and to compute repeatability and reproducibility of the method using either visual or densitometric techniques for the determinative step. Reported results from laboratories using a densitometer showed that, for corn, the relative standard deviation for repeatability (RSDr) for aflatoxin B1 ranged from 56.6 to 41.7% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 ranged from 21.3 to 37.3% and 65.9 to 42.1%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr ranges for aflatoxins B2, G1, and G2 were similar. For reproducibility (R), the RSDR ranges for aflatoxin B1 were 41.7-56.6%, 56.6-84.8%, and 26.4-37.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 95.3, 139.0, and 95.6% for corn, peanut butter, and raw peanuts, respectively. When analysts determined aflatoxin concentrations in corn by visual comparison to standards, the RSDr values for aflatoxin B1 were 47.8-11.4% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 were 76.3-12.6% and 33.4-8.8%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. The RSDR values for aflatoxin B1 were 34.6-90.2%, 45.5-59.3%, and 31.8-78.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 111.0, 157.6, and 92.3% for corn, peanut butter, and raw peanuts, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxin B1↗

PubMed1976

Human cell-mediated cytotoxicity estimated by lymphocyte titration.

Human lymphocyte immunity to tumor-derived target cells was estimated by titrating lymphocyte concentration to achieve a 50% reduction of target cell survival. This lymphocyte titration assay gave estimates of cytotoxicity that were different from those obtained with the conventional cell-mediated cytotoxicity assays but were more proportional to lymphocyte activity. Estimates of cytotoxicity obtained using the lymphocyte titration assay were reproducible upon repeated testin over the course of several months and were relatively unaffected by two- to fourfold variations in target cell concentration. Target cell-specific cytotoxicity was reproducible but often did not appear to be tumor specific.

Antibody Formation↗

PubMed2001

[Accuracy and precision in blood pressure measurement. Comparative study of home self-measurement with measurement in the clinic and out-patient monitoring].

OBJECTIVE: To compare accuracy and precision of self-measurement blood pressure (SMBP) at home, as a diagnosis method of hypertension, with mercury measurement in office and ambulatory blood pressure monitoring (ABPM). DESIGN: A comparison study of diagnosis methods.Setting.Hypertension Unit in the Hospital General de Albacete. PATIENTS: By means of a non-probabilistic sample, selected from consecutive cases that went to the unit, a 64 pharmacologically untreated hypertensive sample older than 18 has been selected. METHODS: All subjects were taken 3 measurements with mercury from a validated nurse in office, and were also taught to make 20 self-measurements of blood pressure in the morning at the office and 20 self-measurements in the evening at home with an automatic device Omron 705-CP, during the same day they were set a Takeda TM-2420 device programmed to measure their blood pressure for 24 hours. All proceedings were repeated 4 weeks later. Mean blood pressure values have been compared with every diagnosis method and sensitivity, specificity, positive and negative predictive value have been studied in every method reproducibility in every method has been analyzed. RESULTS: Subjects were 29 men and 35 women with a mean of 53 years old. The mean values of office blood pressure (OBP) have been higher than SMBP and ABPM in the two periods of the study. SMBP has had a higher specificity and predictive value than OBP. Reproducibility of repeated SMBP in standardized conditions is similar to ABPM. CONCLUSIONS: With a minimum program self-measurements at home, in standardized conditions, they can be considered as an accurate technique in the diagnosis of hypertension.

Adult↗

PubMed1998

Construction and calibration of a low-cost bandage pressure monitor.

This study describes the construction and calibration of a three-channel bandage pressure monitor and evaluates its in-service use. The monitor was constructed from a range of commercially available, relatively inexpensive components consisting of a pressure sensor, piezoresistive transducer, differential amplifier and liquid crystal display. The pressure sensors show a good ratio of thickness to surface area (< 10%) and are sufficiently robust and flexible to conform to most anatomical profiles. The transducers are internally calibrated and temperature-compensated to provide an accurate and stable measurement of gauge pressure relative to atmospheric pressure. During laboratory assessment and in-service use, the system has proved to be reliable, accurate (typically < +/- 0.5 mmHg) and reproducible over repeated calibration.

Bandages↗

PubMed2004

Influence of the quality of tibial plateau alignment on the reproducibility of computer joint space measurement from Lyon schuss radiographic views of the knee in patients with knee osteoarthritis.

RATIONALE: The quality of medial tibial plateau (MT-Plateau) alignment is one of the key elements for accuracy and sensitivity to change of knee radiography in knee osteoarthritis (OA). AIM: To evaluate the influence of the quality of the MT-Plateau alignment on the reproducibility of joint space width (JSW) measurement in knee radiographs. METHODS: One hundred and twenty-seven knee radiographs (99 OA), performed using a standardized radiographic procedure (Lyon schuss (LS) view). Evaluation of the quality of MT-Plateau alignment. Computerized measurement of the JSW, twice, 1-month apart, using a semi-automated and an automated method of measurement. Assessment of the reproducibility of repeated measurements: calculation of intra-observer coefficient of correlation, smallest detectable difference (SDD) and coefficient of variation (CV). RESULTS: MT-Plateau alignment was satisfactory in 99 radiographs (77.9%). Reproducibility was excellent in both satisfactory and non-satisfactory radiographs, irrespective of the method of measurement used. The automated measurement was more reproducible than the semi-automated one (CV 1.15% and 3.23%). SDD and CV were better in satisfactory than in non-satisfactory MT-Plateau aligned radiographs. CONCLUSION: These results confirm that computer measurement of the medial tibio-femoral JSW, from LS digitized radiographs, is highly reproducible, irrespective of the quality of the radiograph. However, the quality of the MT-Plateau alignment influences the reproducibility of JSW measurement. The automated measurement was more reproducible than the semi-automated one.

Aged↗

PubMed2003

Repeated thrombus formation immediately following carotid endarterectomy.

A 56-year-old male presented with thrombus formation manifesting as cerebral embolic infarction suspected to be caused by hemostasis at the carotid bifurcation, not by the intimal abnormalities or hematological disorders. Thrombus repeatedly and reproducibly appeared at the same area in spite of carotid endarterectomy (CEA). Ultrasonography demonstrated a stenotic lesion of the cervical carotid bifurcation. Medical treatment reduced the stenosis, but the thrombus was repeatedly formed at the same area of the cervical carotid bifurcation. CEA was performed. Histological examination of the specimen found only the underlying thin intima consisting of mild fibrous atheromatic change without ulceration or vascular dissection. Ultrasonography following CEA showed reduced blood flow, indicating hemostasis, and moyamoya appearance in that area. The thrombus had recurred in spite of the medical treatment with anti-platelet agent. This repeated thrombus was gradually dissolved and reduced with anticoagulant therapy. Thrombus causing cerebral embolic stroke and originating at the cervical carotid bifurcation is usually due to the intimal atherosclerotic change such as ulcer formation or vascular dissection. The thrombus in this case was probably formed by hemostasis at the cervical carotid bifurcation and CEA was not effective to prevent recurrence.

Carotid Arteries↗

PubMed1985

Reproducibility of skin sensitivity using a quantitative skin prick test.

The reproducibility of repeated quantitative skin prick test titrations was evaluated in seven asthmatic patients tested 2-4 times within 6 weeks. The skin sensitivity was estimated as endpoint titration and histamine equivalent reaction using both 1 and 10 mg/ml histamine dihydrochloride. The histamine equivalent reaction had a significantly higher reproducibility compared to endpoint titration, with a coefficient of variation less than 10% for histamine 10 mg/ml. Further, using this histamine concentration, the deviation in repeated testing was for practical purposes less than 0.5 log step. The same constancy in skin sensitivity was found in one patient tested 3 times and then retested another 3 times 6 months later by a different tester. The results indicate that the quantitative skin prick test and histamine-estimated skin sensitivity have a clinical application in the assessment of pharmacologically or immunotherapy-induced changes in the releasability of skin mast cells.

Adult↗

PubMed1997

Reproducibility of the signal averaged P wave: time and frequency domain analysis.

OBJECTIVE: To assess the reproducibility of time and frequency domain variables derived from the signal averaged P wave. DESIGN: Longitudinal within patient study. SETTING: Regional cardiothoracic centre. PATIENTS: 20 patients (10 with documented paroxysmal atrial fibrillation and 10 normal controls) were studied on three occasions to assess the reproducibility of repeated signal averaged P wave recordings. Digital P wave recordings were made on a further 10 patients on a single occasion and the recordings signal averaged twice in order to assess the reproducibility of the averaging system itself in the absence of biological variation. MAIN OUTCOME MEASURES: P wave duration, spatial velocity, and energies contained in frequency bands from 20, 30, and 60-150 Hz of the P wave spectrum were measured after P wave specific signal averaging. Coefficients of reproducibility were calculated for paired signal averaged P waves derived by signal averaging the same digital recordings on two separate occasions, for recordings performed in the same patients immediately after each other ("back to back") and those performed one week apart. RESULTS: System reproducibility when the same digital P wave recordings were signal averaged on two separate occasions was high (< 11% for all variables). For P wave duration the coefficient of reproducibility was 11.4% for back to back recordings and 13.1% for those one week apart. The reproducibility of spatial velocity and P wave energy was low. Variation in P wave morphology was noted when successive P waves from the same subject were examined. If recordings with the same P wave morphology were analysed the reproducibility of spatial velocity and P wave energy improved but remained significantly poorer than that for P wave duration. CONCLUSIONS: P wave duration is reproducible within subjects in the short and medium term. Frequency domain and spatial velocity analysis are poorly reproducible, due more to spontaneous variation in P wave morphology than to instability of the signal averaging process. This may limit the utility of signal averaged P wave variables other than duration for the prediction of atrial arrhythmia.

Adult↗

PubMed1996

The effect of saline iontophoresis on skin integrity in human volunteers. I. Methodology and reproducibility.

This study, conducted in 36 human volunteers, was an evaluation of the effects of saline iontophoresis on skin temperature, irritation, and barrier function. The major objectives were to assess the effects of low-level ionic currents, to validate the proposed methodology of assessment, and to establish reproducibility in repeated saline iontophoresis applications. This was the first of a multistage study designed to assess the safety of 24-hr saline iontophoresis episodes at selected currents and current densities. Since an iontophoresis patch challenges the skin barrier both by occluding the skin surface and by passing ionic current through the skin, the experimental protocol was designed to permit measurement of the contribution of each of these processes to the overall response. In this first stage we investigated the effect of 10 min of current delivery, at 0.1 mA/cm2 on a 1-cm2 area patch and 0.2 mA/cm2 on a 6.5-cm2 area patch compared to unpowered control patches. Twelve subjects were tested under each condition on two separate occasions to examine reproducibility of the response variable measurements. A further 12 subjects were tested once under the 0.2 mA/cm2, 6.5-cm2 condition. Skin irritation was evaluated via repeated measurements of transepidermal water loss, capacitance, skin temperature, skin color, and a visual scoring system, before the iontophoresis episode and after patch removal. No damage to skin barrier function in terms of skin-water loss or skin-water content was detected. Slight, subclinical, short-lasting erythema was observed for both conditions. Assessment of correlation coefficients showed highly statistically significant indications of reproducibility for all five response variables measured. The experimental design, in combination with a repeated measures analysis, provided clear separation of the occlusion and ionic current components of the iontophoretic patch challenge. Further, the repeated measures analysis gave a highly sensitive assessment of skin irritation and resolution after patch removal. We conclude that the experimental methodology is appropriate for assessing possible changes in skin integrity resulting from saline iontophoresis under similar operating conditions for longer durations and for other skin challenges from which a subclinical response is expected.

Body Temperature↗

PubMed1997

Normal brain volume measurements using multispectral MRI segmentation.

The performance of a supervised k-nearest neighbor (kNN) classifier and a semisupervised fuzzy c-means (SFCM) clustering segmentation method are evaluated for reproducible measurement of the volumes of normal brain tissues and cerebrospinal fluid. The stability of the two segmentation methods is evaluated for (a) operator selection of training data, (b) reproducibility during repeat imaging sessions to determine any variations in the sensor performance over time, (c) variations in the measured volumes between different subjects, and (d) variability with different imaging parameters. The variations were found to be dependent on the type of measured tissue and the operator performing the segmentations. The variability during repeat imaging sessions for the SFCM method was < 3%. The absolute volumes of the brain matter and cerebrospinal fluid between subjects varied quite large, ranging from 9% to 13%. The intraobserver and interobserver reproducibility for SFCM were < 4% for the soft tissues and 6% for cerebrospinal fluid. The corresponding results for the kNN segmentation method were higher compared to the SFCM method.

Adult↗

PubMed2006

Determination of total bilirubin in whole blood from neonates: results from a French multicenter study.

BACKGROUND: Jaundice is frequent in neonates and can cause severe complications, especially in premature neonates, particularly the risk of developing acute bilirubin encephalopathy. Our purpose was to verify if determination of total bilirubin (TBIL) in whole blood on an ABL 735 blood gas analyzer with a spectrophotometer module could provide an analytical alternative to chemical methods of TBIL measurement. METHODS: Our multicenter comparative study involved four hospital laboratories. We studied the repeatability and reproducibility of ABL 735 TBIL measurements in two control sera of medium (N1, 58.1 micromol/L) and high (N2, 275.3 micromol/L) TBIL levels. The same study was simultaneously conducted on four chemistry instruments (two LX 20, one Integra 800 and one Hitachi 917) using four Jendrassik-Grof derived methods. At one site, repeatability was performed with two adult whole-blood samples containing low and high TBIL levels (55.1 and 312.6 micromol/L). RESULTS: Repeatability tests provided coefficients of variation (CVs) between 0.67% and 1.86% on the ABL 735 system, vs. 0.35% and 1.96% for the chemistry instruments. Reproducibility tests for the same control sera resulted in CVs between 1.01% and 3.55% for the ABL 735 and between 0.52% and 3.65% for the chemistry instruments. Recovery for the N1 and N2 control sera was 102-120%. A correlation study of TBIL determination in whole blood vs. plasma was conducted on 473 neonatal blood samples. Correlation coefficients between whole blood and plasma TBIL ranged from 0.969 to 0.994. Passing-Bablok equations were y=1.17x+9.7 [site 1 (IP)], y=1.01x+5.6 [site 2 (JPB, MR)], and y=1.00x-20 [site 3 (AS)]. Only 10% of the results fell outside the 10% range in the bias-corrected Bland-Altman difference plot for the ABL 735 method compared to traditional laboratory methods. CONCLUSIONS: The ABL 735 instrument is reliable for measuring TBIL in 70-microL whole blood samples from neonates. Thus, this method might allow significant blood savings in preterm neonates. Correlation with the reference method for plasma or sera must be established to ensure good follow-up of patients.

Bilirubin↗

PubMed2002

The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting.

PURPOSE: To evaluate the performances of Humphrey Atlas 991, Orbscan II, Dicon CT200, Medmont E300 on young Chinese adults. METHODS: Three sets of corneal topography measurements were obtained from each topographer from 22 subjects-two sets by the same examiner and one set by another examiner on the same day. RESULTS: There were no significant within-examiner and between-examiner differences for any of the parameters tested for each topographer. However, only the repeatability and reproducibility (of apical radius[Ro], eccentricity, and elevation) of the Humphrey and Medmont were good. There was no statistically significant between-topographer difference in R(o), but significant differences in eccentricity and elevation values were found. The number of repeated readings that should be taken for a precision of 2 microm (elevation) were 12 for the Humphrey and 2 for the Medmont. CONCLUSIONS: The performance of both the Humphrey and the Medmont was very good. R(o) and eccentricity values of different topographers cannot be used interchangeably, but the agreement in elevation values was good for these topographers. The number of repeated readings required for maximum precision varies with the topographer used, and they are not interchangeable.

Adult↗

PubMed1998

Reproducibility of ultrasonic fetal volume blood flow measurements.

The intraobserver reproducibility of ultrasonic volume blood flow measurements in the human fetus was evaluated in this study. A new approach, simultaneous measurement of the vessel diameter and the flow velocity with a pulsed-wave Doppler ultrasound synchronized with a real-time ultrasound phase-locked echo-tracking system, was used to estimate volume blood flow (VBF) in the fetal descending aorta. Measurements were performed in a longitudinal study on 20 normally grown fetuses. Intraobserver reproducibility of repeated estimations of mean blood flow velocities throughout gestation was very good, with high values of intraclass correlation coefficient (IntraCC 0.80-0.91) and low values of coefficient of variation (CV 4-11%). The IntraCC of repeated vessel diameter measurements throughout gestation was low (0.30-0.68), whereas the values of CV were acceptable (< 12%), with the exception of the period between 140 and 167 gestational days (CV > 12%). The lower reproducibility of vessel diameter measurement contributed directly to the relatively low reproducibility of VBF estimations overall (IntraCC 0.25-0.70; CV 17-28%), as these are calculated from a formula using both flow velocity and vessel diameter. Nevertheless, the synchronized approach gives absolute values of vessel diameter, flow velocity and VBF comparable with values reported in the human fetus previously. The new method provides, by taking the vessel wall pulsations into consideration and by measuring diameter and velocity simultaneously, a more complete information on fetal haemodynamics and fetal physiology.

Aorta, Thoracic↗