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Results for “Repeatability and Reproducibility”

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PubMed1990

Quantitative chamber angle measurement utilizing image-processing techniques.

An image-processing technique was applied to the measurement of the anterior chamber angle. The anterior eye segment was documented by a new instrument, named anterior eye segment analysis system for biometry of the anterior eye segment. The approximated curve of the corneal posterior curvature and the line tangent to the anterior surface of the iris were calculated as the anterior chamber angle. The mean error of the reproducibility of repeated measurements for the same image was 1.6 +/- 0.81% and that of 3 images of the same eye which were taken at 3 different times was within 5.2%.

Adult↗

PubMed1980

Relationship between concentration and anticoagulant effect of heparin in plasma of normal subjects: magnitude and predictability of interindividual differences.

The purposes of this investigation were to determine the magnitude of inter- and intraindividual variations in the relationship between heparin concentration and anticoagulant effect in normal adults, and to determine whether these variations are asociated with, and therefore predictable from, certain physiologic characteristics of individual subjects. Citrated plasma was obtained from 12 men and 5 women, 21 to 35 yr old. Heparin was added to the plasma to yield concentrations of 0.05 to 1.0 U/ml and the activated partial thromboplastin time (APTT) was determined. These studies were repeated once or twice over 65 days. Baseline APTT values (i.e., ATPP without added heparin) ranged from 25.6 to 36.2 sec and the hematocrit ranged from 39% to 50%. Both measures showed little intrasubject variation on the same day or on different days. There was an excellent linear relationship between In APTT and heparin concentration in the 0.05- to 0.8-U/ml range (r2 > 0.987 in all cases). The slope value for this relationship ranged from 1.51 to 3.88 ml/U and these interindividual differences were well reproducible on repeated testing. Women had lower hematocrits (p < 0.05) and higher slope values (p < 0.01) than men. Multiple linear regression analysis revealed a linear relationship between observed slope values and slope values calculated as a function of both hematocrit and baseline APTT. Age, weight, and the concentrations of various plasma proteins did not contribute significantly to the predictability of the slope. A multiple linear regression equation with hematocrit and baseline APtt as independent variables yielded a multiple correlation coefficient of 0.875 (p < 0.01). Thus, it may be possible to predict the APTT value produced by a given concentration of heparin in an individual subject from the subject's baseline APTT and hematocrit.

Adult↗

PubMed2006

Do skin prick and conjunctival provocation tests predict symptom severity in seasonal allergic rhinoconjunctivitis?

BACKGROUND: In the investigation of seasonal allergic rhinoconjunctivitis (SAR), quantitative skin and conjunctival allergen challenge tests are used to measure individual allergen sensitivity. These tests are reproducible and relate well to prevalence but their relationship to symptom severity is less well established. OBJECTIVE: We wished to determine if quantitative skin prick tests (QSPT) and conjunctival provocation tests (CPTs) using a single grass pollen allergen extract are reproducible and predict symptom severity in SAR. METHODS: We retrospectively analysed data from 91 participants in a previously published randomized placebo controlled study of low dosage allergen immunotherapy who were randomized to receive placebo treatment. We examined the relationship between pre-seasonal QSPT, CPT and SAR symptoms. RESULTS: We found a high level of reproducibility when repeated measures were compared for both the QSPT (P < 0.001) and the CPT (P < 0.001) and moderate correlation (0.49) between the standard skin prick test (SPT) and the QSPT (P < 0.001). We found weak negative correlation (-0.27) between the QSPT and the CPT (P < 0.001). We found no correlation between seasonal symptom, use of rescue medication or quality of life (QOL) scores and pre-seasonal QSPT or CPT. Conclusion In the assessment of seasonal rhinoconjunctivitis, quantitative skin and conjunctival allergen challenge tests are strongly reproducible, although there is no correlation between these tests and seasonal symptom, use of rescue medication or QOL scores.

Adolescent↗

PubMed1998

Evaluation of polarographic measurements of basal muscle oxygen tension in type I diabetic patients.

Microcirculatory changes occur early in insulin-dependent diabetes mellitus (IDDM) and are believed to be an early feature of late diabetic complications, leading to reduced oxygen pressure and hypoxia in the skin and other tissues. Whether muscle oxygen supply is also altered is unknown. Therefore, the authors analyzed polarographic measurements of muscle oxygen tension in 44 healthy type I diabetic patients (mean age 28 years; mean diabetes duration 7 years) and in 57 healthy controls, matched for age, sex, and body mass index, and the corresponding influencing factors. Two measurements were taken at rest 60 minutes apart in the anterior tibial muscle. Muscle oxygen tensions did not differ between IDDM patients and controls (23.0 +/- 8.6 vs 25.3 +/- 9.0 mmHg) and were reproducible on repeated measurements (25.3 +/- 9.7 vs 25.5 +/- 7.4 mmHg). Coefficients of variation were 13.5 +/- 10.8% in IDDM patients and 13.1 +/- 9.3% in controls. Compared with controls, in IDDM patients hemoglobin A1c (HbA1c) and blood glucose concentrations were elevated, and arterial oxygen pressure was significantly lower. Muscle oxygen tensions were positively correlated with blood glucose concentrations in IDDM patients (Rho=0.48, P=0.002) but not with HbA1c or with insulin concentrations. The authors conclude that the polarographic measurement of muscle oxygen tension is a reliable method with good reproducibility. Hypoxia in the anterior tibial muscle of type I diabetic patients can be excluded. In IDDM patients the level of muscle oxygen tension is correlated with the level of blood glucose concentration.

Adult↗

PubMed1988

Reproducibility of CT bone densitometry: operator versus automated ROI definition.

Intrasubject reproducibility with repeated determination of vertebral mineral density from a given set of CT images was investigated. The region of interest (ROI) in 10 patient scans was selected by four independent operators either manually or with an automated procedure separating cortical and spongeous bone, the operators being requested to interact in ROI selection. The mean intrasubject variation was found to be much lower with the automated process (0.3 to 0.6%) than with the conventional method (2.5 to 5.2%). In a second study, 10 patients were examined twice to determine the reproducibility of CT slice selection by the operator. The errors were of the same order of magnitude as in ROI selection.

Algorithms↗

PubMed1997

Study of the uterine response to vaginal distension: the 'vagino-uterine reflex'.

To study the effect of vaginal distension on the uterus, the uterine pressure was measured in 20 healthy female volunteers (mean age 34.3 +/- 7.8 years; 7 nulli-, 13 multiparous) by means of a manometric tube perfused by a pneumohydraulic system. Vaginal distension was induced by a 12 F condom-ended catheter. The condom was inflated in increments of 10 ml of air. The test was repeated after anesthetizing the vagina and uterus, respectively. The uterine pressure increased upon vaginal distension; it showed more rise as the distension increased (p < 0.01). The response was momentary and the pressure returned to basal values although vaginal distension continued. It disappeared upon sustained or successive inflations of 5-7 times and was restored after a resting period of 3-5 min. There was no uterine pressure response when the vagina or uterus were anesthetized and it returned when the anesthetic effect had worn off. No significant difference was found in the pressure response between nulli- and multiparous women (p > 0.05). The aforementioned results were reproducible when repeated in the same woman with no significant difference (p > 0.05). The inflated condom looks like the erect penis, and the uterine response to the inflated condom seems to simulate that of the erect penis distending the vagina during coitus. The constant rise of uterine pressure to vaginal distension postulates a reflex relation which we call 'vagino-uterine' reflex. Uterine contractions during coitus are suggested to have a 'suction-pumping' action on the semen deposited in the vaginal fornices.

Adult↗

PubMed1994

Critical evaluation of the use of skin tests and cellular tests in standardization of allergens.

In two groups of 8 and 40 allergic patients repeatedly skin-tested with various dilutions of timothy allergen and with histamine (10 mg/ml) intradermally and by prick test, the skin reactions were evaluated by wheal and erythema size at 20 minutes and kinetically followed over 60 minutes by infrared telethermography. The latter technique permits to define further reaction parameters, such as thermographic area and Thermographic Units based on the average elevation of temperature in the reaction site. These studies have led to several conclusions. First, the skin area really involved in skin reactions to allergens or to histamine are much larger than assessed visually. There is more to it than meets the eye. Second, among all parameters studied in terms of reproducibility upon repeated testing, erythema and thermographic areas are the most stable, while wheal area shows considerably larger variations. Third, there is no good correlation between reactions to allergen dilutions and reactions to histamine, either individually or as groups of patients. In addition, the ratio of thermographic area (as true indication of allergic inflammation) to erythema area and the kinetics of the reaction are very different between allergen-induced and histamine-induced reactions. There is therefore no real advantage in relating reactions to allergen to reactions to histamine, in terms of biological standardization. Fourth, the intradermal technique, in terms of reactions to histamine, definitely shows better reproducibility than the prick test technique in skilled hands. A method such as the HEP standardization technique, combining prick testing, evaluation of skin reactions by wheal area and reference to a histamine standard is therefore the worst of possible alternatives. The US method, based on intradermal injection of various dilutions of allergen and evaluation of erythema, seems to us more adequate and reproducible for quantitative biological standardization of allergen extracts by skin testing. This statement does not mean that prick testing could not nevertheless be considered as a method of choice for diagnostic skin testing.

Allergens↗

PubMed2002

High-resolution, spin-echo BOLD, and CBF fMRI at 4 and 7 T.

With growing interest in noninvasive mapping of columnar organization and other small functional structures in the brain, achieving high spatial resolution and specificity in fMRI is of critical importance. We implemented a simple method for BOLD and perfusion fMRI with high spatial resolution and specificity. Increased spatial resolution was achieved by selectively exciting a slab of interest along the phase-encoding direction for EPI, resulting in a reduced FOV and number of phase-encoding steps. Improved spatial specificity was achieved by using SE EPI acquisition at high fields, where it is predominantly sensitive to signal changes in the microvasculature. Robust SE BOLD and perfusion fMRI were obtained with a nominal in-plane resolution up to 0.5 x 0.5 mm(2) at 7 and 4 Tesla, and were highly reproducible under repeated measures. This methodology enables high-resolution and high-specificity studies of functional topography in the millimeter to submillimeter spatial scales of the human brain.

Adult↗

PubMedDate not supplied

Vitamin D in infant formula and enteral products by liquid chromatography: collaborative study.

Results from a collaborative study of a new liquid chromatographic (LC) method for determination of vitamin D in infant formulas and enteral products are presented. Each of 15 laboratories was provided with 11 blind duplicate samples covering a range of approximately 200-500 International Units/quart (normal dilution), a system suitability sample, and the U.S. Pharmacopeia ergo- and cholecalciferol standards. Product types included liquid and powder forms of milk (whey and casein), soy, and hydrolyzed protein-based infant formulas and enteral products. The method includes a single liquid-liquid extraction following saponification, solid-phase extraction, and then concentration by evaporation. An isocratic, nonaqueous, chromatographic system with reversed-phase, zero endcapped C18 column, and UV detector set at 265 nm are used. Statistical evaluation of data from participating laboratories show the average reproducibility and repeatability of the method across all samples to be excellent, with RSDR and RSDr values of 13.48 and 9.44, respectively, after elimination of outliers. The LC method for determination of vitamin D in infant formulas and enteral products has been adopted by AOAC INTERNATIONAL.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Liquid chromatographic method for multiresidue determination of benzimidazoles in beef liver and muscle: collaborative study.

A liquid chromatographic method for determination of thiabendazole, 5-hydroxythiabendazole, oxfendazole, mebendazole (MBZ), and fenbendazole (FBZ) in cattle liver and muscle was collaboratively studied in 7 laboratories in 1986. For blind fortified samples containing 800 ppb FBZ, average recovery and relative standard deviations for repeatability and reproducibility (RSDr and RSDR) based on results from 6 of the participating laboratories were 83%, 12.7%, and 14.0%, respectively. Recoveries of FBZ from incurred liver samples were more variable. Recoveries of MBZ from livers fortified at the 100 ppb level were encouraging; however, the drug levels were too low in the incurred samples used for MBZ studies. Except for FBZ and MBZ in liver, the study data were not satisfactory. The method has been adopted official first action by AOAC for determination of 800-1600 ppb fenbendazole in liver. The analysis should be repeated using a smaller sample size when initial analyses show levels greater than 1600 ppb FBZ.

Animals↗

PubMed2006

[Reproducibility of Fuhrman nuclear grade: advantages of a two-grade system].

The Fuhrman nuclear grade is the reference histoprognostic grading system routinely used all over the world for renal cell carcinoma. Studies measuring the inter-observer and intra-observer concordance of Fuhrman grade show poor results in terms of reproducibility and repeatability. These variations are due to a certain degree of subjectivity of the pathologist in application of the definition of tumour grade, particularly nuclear grade. Elements able to account for this subjectivity in renal cell carcinoma are identified from a review of the literature. To improve the reliability of nuclear grade, the territory occupied by the highest grade must be specified and the grades should probably be combined. At the present time, regrouping of grade 1 and 2 tumours as low grade and grade 3 and 4 tumours as high grade would achieve better reproducibility, while preserving the prognostic: value for overall survival. The development of new treatment modalities and their use in adjuvant situations will imply the use of reliable histoprognostic factors to specify, indications.

Carcinoma, Renal Cell↗

PubMed2001

Three-dimensional echocardiography with tissue harmonic imaging shows excellent reproducibility in assessment of left ventricular volumes.

We studied the reproducibility of repeated measurements of left ventricular (LV) volumes by 2-dimensional (biplane method of disks) and 3-dimensional echocardiography (coaxial scanning) with tissue harmonic imaging. Ten healthy subjects underwent estimation of LV volumes by transthoracic echocardiography twice within 1 week by 2 different operators to investigate interexamination and operator variance. In addition, the analysis of LV volume was done manually by 2 observers to assess both interobserver and intraobserver variances. With 3D echocardiography, observer variation had the greatest impact on variance. Operator variability showed important contributions to total variance with the use of 2D echocardiography. The reproducibility of 3D echocardiography and tissue harmonic imaging is excellent and comparable to magnetic resonance imaging techniques; 3D echocardiography therefore should provide a powerful tool for noninvasive LV volume estimation.

Adult↗

PubMed1999

An automated technique for the simultaneous determination of cations in nanoliter volumes.

BACKGROUND: The study of ion transport along the renal tubule in vivo or in vitro requires a technique capable of analyzing ion concentrations in sample volumes of only a few nanoliters. This article describes a method for the analysis of cations at physiological concentrations in samples of tubular fluid taken from single renal tubules in vivo. Method. A background electrolyte composed of 2-[N-Morpholino] ethane-sulfonic acid (MES) (50 mmol/liter) and L-histidine (50 mmol/liter; pH congruent with 6.2), with the additives 18-crown-6 (1 mmol/liter) and methanol (30%) was used for the cation separation combined with conductivity detection. RESULTS: Capillary zone electrophoresis was used to separate NH4, K, Na, Ca, Li, Mg, and Ba in six minutes. Simultaneous quantitative analysis was performed for sodium and potassium, providing detection limits of 0.2 pmol for sodium and 30 fmol for potassium. The calibration plots were linear over three orders of magnitude, including the range of interest to clinical analysis. Data on the reproducibility and repeatability of peak areas and of the repeatability of migration times are reported. CONCLUSION: The results for sodium and potassium are in close agreement with those obtained by atomic absorption spectrometry, indicating that this is a suitable technique for the routine measurement of these cations in tubule fluid samples.

Automation↗

PubMed2003

Artificial reproduction of atypical hydRoa vacciniforme caused by latent EpStein-Barr virus infection.

BACKGROUND: Cases of hydroa vacciniforme-like eruptions caused by latent Epstein-Barr virus (EBV) infection have been reported in Asia and Mexico, some of which progressed to lymphoproliferative disorders. The precise clinical features of the disease are not, however, clear. METHODS: We performed an artificial provocation test with repeated exposures of ultraviolet A (UVA) and UVB in an 8-year-old Korean girl who had severe hydroa vacciniforme-like skin eruptions on exposed areas. RESULTS: The patient showed features of latent EBV infection serologically, and an in situ hybridization study indicated that most infiltrating mononuclear cells in the dermis were positive for EBV. After three exposures to UVA irradiation with a total dose of 90 J/cm2, erythema and vesicles appeared on the UVA-irradiated site but not on the UVB-irradiated site. CONCLUSIONS: Atypical hydroa vacciniforme caused by latent EBV infection could be reproduced by repeated UVA irradiation. Further study on the photo-protection would be necessary to prevent its progression to lymphoproliferative malignancies.

Child↗

PubMed2004

Continuous microwave-assisted extraction coupled with derivatization and fluorimetric monitoring for the determination of fluoroquinolone antibacterial agents from soil samples.

An automated screening approach for fluoroquinolone (FQ) antibiotics (norfloxacin and ciprofloxacin) in soil samples has been developed. The proposed approach consists on dynamic microwave-assisted extraction and subsequent real-time on-line monitoring of the analytes extracted; thus, the extraction is halted when complete leaching of the analytes has been reached (independently of the sample matrix), avoiding extraction times in excess. The end of the extraction allowed quantifying the total content of the analytes. The extraction was carried out using pure water as extractant and consisted of a number of extraction cycles (depending on the sample matrix) in which the sample was subjected to microwave irradiation while the direction of the extractant was changed in an iterative manner. The target analytes were fluorometrically monitored after derivatization with a terbium (Tb3+)/tri-n-octylphosphine oxide (TOPO)/cetylpyridinium chloride (CPCl)/acetate buffer solution. Optimum conditions for analytes extraction and formation of FQ-Tb3+-TOPO ternary complexes have been obtained using the experimental design methodology. The mean recoveries from soil samples spiked with 5 and 0.5 microg/g of each analyte were (95.2+/-4.16%) and (98+/-5.21%), respectively. The within-laboratory reproducibility and repeatability, expressed as relative standard deviation, were 7.29 and 5.80%, respectively. The approach only allows monitoring of the overall content of the species that yield fluorescent complexes with the derivatizing reagent, so the use of chromatography is mandatory for individual separation/quantification of the target compounds.

Anti-Bacterial Agents↗

PubMed2005

Stir bar sorptive extraction for the determination of volatile compounds in oak-aged wines.

Stir bar sorptive extraction (SBSE) followed by a thermal desorption-gas chromatography-mass spectrometry analysis has been optimized for the determination of 13 of the most important oak volatiles in wine samples, all in a single run. The stir bar sorptive extraction method was optimized in terms of temperature, time, pH and NaCl addition, and the best results were obtained after stirring the wine sample with the polydimethylsiloxane stir bar during 90min at room temperature. The addition of sodium chloride did not enhance the volatile extraction. The method proposed showed good linearity over the concentration range tested, with correlation coefficients ranging from 0.92 to 0.99 for all the analytes. The reproducibility and repeatability of the method was estimated between 0.11 and 5.45%. The detection and quantification limits of all analytes were lower than their respective olfactory threshold values, and, most importantly, no artifacts have been observed during the analysis as described in most extractions using other current methodologies.

Flavoring Agents↗

PubMed2001

Simultaneous determination of flucytosine and fluorouracil in human plasma by high-performance liquid chromatography.

A validated, sensitive and precise reversed-phase high-performance liquid chromatographic method for the simultaneous determination of 5-flucytosine (5-FC) and 5-fluorouracil (5-FU) in human plasma is described. Two compounds, 5-methylcytosine (5-MC) and 5-chlorouracil (5-CU), were used as internal standards for the determination of 5-FC and 5-FU, respectively. Plasma samples were deproteinized with trichloroacetic acid and chromatographed on an octylsilica column, maintained at 30 degrees C during elution, using a 0.04 M phosphate buffer, pH 7.0, as eleunt. Spectrophotometric diode array detection was used at 266 nm. 5-FC, 5-FU, 5-MC and 5-CU were found to have retention times of 4.8, 5.8, 7.7 and 11.0 min respectively. Recoveries of 91-120% with reproducibility and repeatability coefficients of variation of 0.8-6% were obtained. Mean correlation coefficients of 0.99989 and 0.9995 were found for the linear calibration curves (n = 2) of 5-FC (4.816-192.6 mg/l) and 5-FU (0.05368-5.368 mg/l), respectively. The limits of quantitation were 0.3 mg/l for 5-FC and 0.05 mg/l for 5-FU.

Calibration↗

PubMed2006

Evaluation of different strategies for the development of amperometric biosensors for L-lactate.

Two strategies were investigated for the development of lactate biosensors based on sol-gel matrixes and polysulfone composite films, both containing L-lactate dehydrogenase (LDH). Firstly, reagentless disposable screen-printed electrodes (SPE's) with Meldola's Blue (MB) and the cofactor NAD(+) inside a sol-gel matrix were prepared. These showed relatively low sensitivities (260 microA/M). Secondly, mediator-modified-polysulfone-graphite composite films deposited over both cylindrical epoxy-graphite and SPE's. These electrodes showed enhanced performance characteristics: improved sensitivity (80 mA/M), detection limit (0.87 microM) and reproducibility (2%). Reagentless electrodes, incorporating NAD(+) in the polysulfone film, had a decreased sensitivity, although better than that achieved by the sol-gel electrodes. While sol-gel electrodes showed a linear range between 1.25 x 10(-4) and 2.48 x 10(-3)M, the epoxy-graphite composite electrodes based on polysulfone composite films allowed the detection of lactate at a linear range of lower concentrations from 1 x 10(-6) to 1.2 x 10(-5)M. Finally, the performance of the LDH-MB-polysulfone-composite film-based SPE's in a flow system was studied. Short response times were obtained (t<30s). Furthermore, repeatability and reproducibility values were notably improved, especially when working with electrodes covered with a polyamide layer prepared with N-(2-aminoethyl)-piperazine.

Biosensing Techniques↗