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At least 595 records · Page 33Linked to original sources
PubMed2006

Comparison of three methods for beat-to-beat-interval extraction from continuous blood pressure and electrocardiogram with respect to heart rate variability analysis.

In recent years the analysis of heart rate variability (HRV) has become a suitable method for characterizing autonomous cardiovascular regulation. The aim of this study was to investigate the differences in HRV estimated from continuous blood pressure (BP) measurement by different methods in comparison to electrocardiogram (ECG) signals. The beat-to-beat intervals (BBI) were simultaneously extracted from the ECG and blood pressure of 9 cardiac patients (10 min, Colin system, 1000-Hz sampling frequency). For both data types, slope, peak, and correlation detection algorithms were applied. The short-term variability was calculated using concurrent 10-min BP and ECG segments. The root mean square errors in comparison to ECG slope detection were: 1.74 ms for ECG correlation detection; 5.42 ms for ECG peak detection; 5.45 ms for BP slope detection; 5.75 ms for BP correlation detection; and 11.96 ms for BP peak detection. Our results show that the variability obtained with ECG is the most reliable. Moreover, slope detection is superior to peak detection and slightly superior to correlation detection. In particular, for ECG signals with higher frequency characteristics, peak detection often exhibits more artificial variability. Besides measurement noise, respiratory modulation and pulse transit time play an important role in determining BBI. The slope detection method applied to ECG should be preferred, because it is more robust as regards morphological changes in the signals, as well as physiological properties. As the ECG is not recorded in most animal studies, distal pulse wave measurement in combination with correlation or slope detection may be considered an acceptable alternative.

Adult↗
PubMed2006

Performance characteristics of seven automated thyroxine and T-uptake methods.

BACKGROUND: Estimates of the free thyroxine concentration can be made using measurements of thyroxine (T4) and the thyroid hormone binding ratio (THBR, usually reported as T-uptake) according to the formula free thyroxine index (FTI)=T4xTHBR. We evaluated the performance characteristics of 7 pairs of automated T4 and T-uptake methods. METHODS: We evaluated the Architect i2000, AxSYM, ADVIA Centaur, UniCel DxI 800, Immulite 2000, Modular E170 and Vitros ECi methods for T4 and T-uptake. Imprecision was assessed by duplicate determinations on 3 levels of quality control material per run, 2 runs per day, on 5 separate days. Method comparison studies were performed with 205 patient samples and 68 samples from subjects in the second or third trimester of pregnancy. Results for both imprecision and method comparison were converted to the THBR as outlined by each method's manufacturer. RESULTS: Overall CVs for T4 and THBR methods were 3.2-8.9% and 1.2-6.7%, respectively. T4 methods generally agreed well. The THBR methods did not agree nearly as well. Comparison of FTI results with free T4 by equilibrium dialysis showed good correlation but different slopes. CONCLUSIONS: All methods show adequate precision but the THBR and FTI results are not well standardized.

Thyroxine↗
PubMed2001

Significant precision improvement for temperature mapping.

MR temperature measurements are important for applications such as the evaluation of thermal therapies and radiofrequency (RF) coil heating effects. In this work the spherical mean value (SMV) method has been applied to significantly improve the precision of MR temperature mapping in a homogeneous gel phantom. Temperature-increase maps of the phantom were obtained with three-dimensional (3D) MR phase difference mapping after heating with the RF coil. The temperature-increase distribution in most regions in the phantom is a harmonic function with the mean value property. Based on this property, the precision of temperature-increase maps was improved up to sixfold with the SMV method. Comparison of this method with conventional smoothing, further precision improvement, and the in vivo application of the SMV method are discussed.

Hot Temperature↗
PubMed2006

Multi-center evaluation of analytical performance of the microparticle enzyme immunoassay for sirolimus.

OBJECTIVES: This study evaluated the analytical characteristics of the new Abbott microparticle enzyme immunoassay (MEIA) for sirolimus. DESIGN AND METHODS: The protocol consisted of nine sections: evaluation of antibody specificity, linearity, detection limit, quantification limit, endogenous interferents, exogenous interferents, precision, proficiency testing panel, and method comparison. RESULTS: The mean analytical detection limit was 0.68 microg/L. The sirolimus concentration corresponding to a total CV of 20% was 1.5 microg/L. Linearity of response was demonstrated across the dynamic range of the assay. Total precision (CVs) at QC control levels from 5 to 22 microg/L ranged from 5.7 to 12.6%. Assay standardization was found to be in good agreement with LC/MS/MS as compared with target values for spiked sirolimus proficiency samples from an international sirolimus proficiency testing program. Good correlations (R values) of the immunoassay were observed in comparisons to LC/MS/MS. R values tended to be lower in comparisons with LC/UV methods. Across both LC-based methods and all study sites, there was approximately 25% overall positive slope bias due to cross reactivity of the MEIA antibody to metabolites of sirolimus. The assay cross-reactivity to metabolites of sirolimus parent drug ranged from 6 to 63%. Assay interferences were minimal with the exception of hematocrit, which presented a negative relationship to measured sirolimus concentration. CONCLUSIONS: The MEIA demonstrated acceptable analytical characteristics for use for routine monitoring of sirolimus immunosuppressive therapy, and is a viable alternative to HPLC-based methods for sirolimus monitoring.

Calibration↗
PubMed1991

The use of pulsed amperometry combined with ion-exclusion chromatography for the simultaneous analysis of ascorbic acid and sulfite.

Initial attempts to monitor ascorbic acid and sulfite, in a beer matrix, by combining ion-exclusion chromatography with a pulsed amperometric detector using a single applied voltage to the platinum working electrode, were unsuccessful. Alternatively, good chromatograms for the separation of the two antioxidants were achieved utilizing a standard, amperometric cell. However, remarkably superior results were observed when this standard cell was operated in a pulsed mode and cleaning cycles were continually applied throughout the analysis. The working electrode stability and precision have been examined. Preliminary spike recovery data indicate acceptable accuracy for the method. Comparisons of this method to standard reference methods are currently ongoing.

Ascorbic Acid↗
PubMed1981

The T-test and clinical relevance. Is your beta error showing.

The t-test, as usually performed in the clinical laboratory for methods comparisons, does not consider the clinical relevance of the difference between the methods. Two procedures are presented which incorporate medical criteria into the t-test thereby making it a more relevant statistical tool. This is done by defining beta error in addition to alpha error. Since a positive action; i.e., adoption of the "test" methods, is taken when there is no difference between the "test" and reference methods, commission of a beta error has a potentially damaging effect. Therefore, evaluation of beta error is an appropriate part of methods comparison in the clinical laboratory.

Laboratories↗
PubMedDate not supplied

Death of a lifestyle: the effects of social support and healthcare support on the quality of life of persons with fibromyalgia and/or chronic fatigue syndrome.

PURPOSE: The purpose of this study was to investigate how social support and healthcare support affect the quality of life of persons with fibromyalgia and chronic fatigue syndrome. METHOD: A constant comparison method was used for the qualitative portion of the research and descriptive correlational methods were used for the quantitative portion. CONCLUSION: This mixed design research study suggested that social support, unlike healthcare support, is related to Quality of Life (QOL). It was also evident that subjects suffering from CFS and/or FMS do not experience high levels of social support.

Activities of Daily Living↗
PubMed1988

Application of the molecular replacement method to multidomain proteins. 2. Comparison of various methods for positioning an oriented fragment in the unit cell.

The capabilities of several different methods to determine the correct translation of a model for the application of the molecular replacement method of structure determination to multidomain proteins have been analyzed. The structure of the Fab fragment of the autoimmune anti-poly(dT)-specific antibody HED10 was determined using molecular replacement and provides an example for comparing different methods of determining the correct translation of the model and for evaluating the importance of the parameters used. Expansion to space group P1 and phasing with a correctly oriented randomly positioned model was found to be superior to either the Crowther-Blow translation function [Crowther & Blow (1967). Acta Cryst. 23, 544-548] or a brute-force search when only a small part of the molecule was used as a model.

Antibodies↗
PubMed1989

Non-stereo photographic screening after panretinal photocoagulation for proliferative diabetic retinopathy. Compared with 60D enhanced slit-lamp examination.

135 patients treated with panretinal photocoagulation for proliferative diabetic retinopathy were examined in order to detect 7 specific fibrovascular lesions after treatment. Two presumptive methods for long-term follow-up were evaluated and compared, i.e. slit-lamp biomicroscopy enhanced by a 60 D lens and reading from two non-stereo photographs of the posterior pole. Two observers repeated their examinations with respective methods. Comparison of the methods with respect to detecting ability of the fibrovascular lesions showed no significant disagreement except in some eyes with fibrous tissue on the optic disc where new vessels were better detected with the slit-lamp method (P less than 0.001). There was no difference between the methods with respect to the intra- and inter-observer variability. Twenty to 30 patients could be diagnosed per hour with the photographic method compared to 5-6 patients with the slit-lamp. Two non-stereo photographs of the posterior pole can be recommended as a safe and time-saving method for objective documentation and long-time follow-up after panretinal photocoagulation for proliferative diabetic retinopathy.

Adult↗
PubMed2006

Minimal changes in health status questionnaires: distinction between minimally detectable change and minimally important change.

Changes in scores on health status questionnaires are difficult to interpret. Several methods to determine minimally important changes (MICs) have been proposed which can broadly be divided in distribution-based and anchor-based methods. Comparisons of these methods have led to insight into essential differences between these approaches. Some authors have tried to come to a uniform measure for the MIC, such as 0.5 standard deviation and the value of one standard error of measurement (SEM). Others have emphasized the diversity of MIC values, depending on the type of anchor, the definition of minimal importance on the anchor, and characteristics of the disease under study. A closer look makes clear that some distribution-based methods have been merely focused on minimally detectable changes. For assessing minimally important changes, anchor-based methods are preferred, as they include a definition of what is minimally important. Acknowledging the distinction between minimally detectable and minimally important changes is useful, not only to avoid confusion among MIC methods, but also to gain information on two important benchmarks on the scale of a health status measurement instrument. Appreciating the distinction, it becomes possible to judge whether the minimally detectable change of a measurement instrument is sufficiently small to detect minimally important changes.

Attitude to Health↗
PubMed1982

Personal characteristics of house staff candidates: a quantitative analysis of relative weights.

We surveyed the faculty, fellows, and residents of a department of medicine to determine the relative importance of each of eight personal characteristics evaluated during the interview of house staff candidates. A booklet containing all possible pairings of the eight characteristics was distributed to 219 participants who were asked which member of each pair should have greater weight for assigning an overall interview grade. Usable data were returned by 172 persons (79%) and analyzed by the psychometric scaling method of paired comparisons. The four characteristics with the greatest relative weights were professional attitude, maturity, enthusiasm and energy, and knowledge. The faculty, fellows, and residents were highly consistent in their judgments. However, three of the characteristics (motivation for clinical practice, knowledge, and verbal skill) significantly distinguished the three departmental groups. These results show that utility of the paired comparison method for identifying a department's weighting of variables for selection of house staff.

Attitude of Health Personnel↗
PubMed1976

[Generation and determination of pulmonary distribution disturbances (author's transl)].

Pulmonary distribution disturbances could be generated in patients with bronchial hyperreactivity by inhalation of a Falicain aerosol (Propoxipiperocainhydrochlorid); The inhomogeneities of ventilation and mechanics of breathing were determined by means of several simple and complex methods. Comparison between these methods of analysis of distribution shows that small alterations of inhomogeneity can be indicated also by simple screening tests. The results confirm the significant relationship between ventilation disturbance and pulmonary inhomogeneity. Distribution disturbance enhances both the obstructive and the restrictive component of a ventilation disturbance. These two components cannot be separated exactly by means of the parameters of ventilation and mechanics of breathing because of the influence of inhomogeneity. The generated disturbances of distribution and ventilation became regular after inhalation of an Alupent aerosol.

Aerosols↗
PubMed2001

[A study of artemether combined with primaquine in the treatment of falciparum malaria].

OBJECTIVE: To evaluate the efficacy and side effects of artemether combined with primaquine in the treatment of falciparum malaria. METHODS: Randomization and comparison methods were used in 121 falciparum malaria cases in the Republic of Central Africa. Sixty-one cases were treated with artemether combined with primaquine (Group A used artemether orally, Group B used artemether intramuscularly). And 60 cases received single artemether (Group C used artemether orally, Group D used artemether intramuscularly) were taken as control. RESULTS: In Group A and B the mean fever clearance time were 47.6 +/- 15.7 and 36.9 +/- 10.7 hours, clinical cure rates 84.4% and 100%, relapse rates 6.3% and 3.4%, respectively. In Group C and D the mean fever clearance time were 48.2 +/- 18.4 and 42.2 +/- 9.5 hours, clinical cure rates 90.1% and 96.3%, relapse rates 21.2% and 18.5%, respectively. Side effects in cases of all groups were mild. CONCLUSION: Artemether combined with primaquine and single artemether(via both routes) showed good therapeutic effects in falciparum malaria cases, while artemether combined with primaquine was more effective than single artemether in reducing relapes rate of malaria.

Adolescent↗
PubMed1989

An improved pyrogallol red-molybdate method for determining total urinary protein.

We adapted the pyrogallol red-molybdate method for total urinary protein to the Cobas Bio centrifugal analyzer. The method is simple, rapid, sensitive, and inexpensive. Addition of 25 mg of sodium dodecyl sulfate per liter to the reagent modifies protein reactivities so that the chromogenicity of human gamma globulins is the same as that of albumin. Results by this method and a comparison method that included gel filtration and a modified biuret reaction correlated well (r = 0.951).

Adult↗
PubMed1989

Potential problem with fluorescence polarization immunoassay cross-reactivity to vancomycin degradation product CDP-1: its detection in sera of renally impaired patients.

During the development of a homogeneous immunoassay for the antibiotic vancomycin, we observed in certain patient samples a quantitation difference between the enzyme multiplied immunoassay technique (EMIT) method and the comparison method, fluorescence polarization immunoassay (FPIA). This prompted us to evaluate the integrity of vancomycin in samples from renally impaired patients. Since it has been reported in the scientific literature that vancomycin degrades into an antibiotically inactive crystalline degradation product (CDP-1) in vitro, we developed high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) methods to determine whether CDP-1 is present in patient sera. HPLC and LC/MS analysis on samples from renally impaired patients positively identified CDP-1 in fresh samples. Next, we tested the cross-reactivity of three currently available vancomycin immunoassays, radioimmunoassay (RIA) FPIA, and EMIT, to CDP-1 prepared in our laboratory. Our data suggest that CDP-1 is recognized by FPIA and RIA, both polyclonal antibody-based methods, but not by EMIT, which uses a monoclonal antibody.

Chromatography, High Pressure Liquid↗
PubMed1987

Three commercial kits and one liquid-chromatographic method evaluated for determining 25-hydroxyvitamin D3 in serum.

The accuracy of three commercial kit methods and one liquid-chromatographic (HPLC) method for determining 25-hydroxyvitamin D3 in serum was evaluated by using isotope dilution-mass spectrometry as a reference technique. The kit methods were based on radioimmunoassay and radioreceptor assay. Serum samples were analyzed from male and female volunteers, some of whom had been exposed to ultraviolet B light or given vitamin D3 orally. Results obtained with the three commercial kits were less accurate than those by HPLC. The agreement between the HPLC method and the comparison method was relatively good: r = 0.99; slope = 1.23; intercept = -2.9 micrograms/L. We conclude that methods based on HPLC should be preferred in routine clinical work and that the accuracy of the three commercial kits tested is not sufficient for their intended use.

Calcifediol↗