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At least 91 records · Page 5Linked to original sources
PubMed1991

Development and validation of a protocol for field validation of passive dosimeters for ethylene oxide excursion limit monitoring.

An exposure and analysis protocol is described for the field validation of passive dosimeters for ethylene oxide (EtO) excursion limit monitoring. The protocol calls for the use of a field exposure chamber with concurrent sampling using Tedlar air-sampling bags. The bags are analyzed immediately after sampling by gas chromatography with flame ionization detection (GC-FID). The chamber design allows all monitors to be exposed for the exact same time in the field. The sampling and analysis procedure not only determines the actual concentration of EtO present during the monitor's exposure but estimates if concentrations of EtO vary from point to point in the monitor array during the exposure. In chamber operation, the accuracy of the standard generator used to calibrate the GC-FID was independently verified in the field by the standard additions method. The sampling bias of the sampling train was determined to be -3.5% in the 2.4 ppm to 14.3 ppm concentration range. To estimate the stability of collected EtO samples in Tedlar bags, the rate of EtO loss in the bags was determined to be 0.011 ppm/hr at 2.57 ppm and 0.066 ppm/hr at 8.07 ppm. Sampling bias of the passive methods by additional EtO exposure of the monitors in the closed chamber after sampling and during purging was determined to be +1.5%. The Tedlar bag sampling method with subsequent GC-FID determination demonstrated a coefficient of variation of 1.8% at 2.43 ppm.

Air Pollutants, Occupational↗
PubMed1999

Validity of the body mass index as an indicator of the risk and presence of overweight in adolescents.

The validity of the body mass index (BMI) as an indicator of the risk of becoming overweight and of the presence of overweight was evaluated in 6 groups of adolescents comprising several ethnic groups (n = 1570, aged 9-19 y). With use of triceps skinfold thickness and estimated percentage body fat as the criteria for adiposity, BMI had high specificities (86.1-98.8% for risk of overweight and 96.3-100% for presence of overweight) and lower but variable sensitivities (4.3-75.0% for risk of overweight and 14.3-60% for presence of overweight). Thus, almost all adolescents who were not at risk for overweight or who were not overweight were classified correctly. In contrast, many adolescents who were at risk of overweight or who were overweight were not correctly identified as measured by BMI. Partial correlations, controlling for age, between BMI and the triceps skinfold thickness and estimated percentage body fat were generally moderate to moderately high, whereas BMI and triceps skinfold thickness appeared to be equally related to estimated total body fatness and percentage body fat in Mexican American and Austrian white males. BMI was better correlated with trunk skinfold thicknesses, but when relative subcutaneous fat distribu-tion was statistically controlled, the trunk-extremity contrast in the correlations was no longer apparent.

Journal Article↗
PubMed1985

Validation of attenuation-corrected equilibrium radionuclide angiographic determinations of right ventricular volume: comparison with cast-validated biplane cineventriculography.

To determine the accuracy of attenuation-corrected equilibrium radionuclide angiographic determinations of right ventricular volumes, we initially studied 14 postmortem human right ventricular casts by water displacement and biplane cineventriculography. Biplane cineventriculographic right ventricular cast volumes, calculated by a modification of Simpson's rule algorithm, correlated well with right ventricular cast volumes measured by water displacement (r = .97, y = 8 + 0.88x, SEE = 6 ml). Moreover, the mean volumes obtained by both methods were no different (73 +/- 28 vs 73 +/- 25 ml). Subsequently, we studied 16 patients by both biplane cineventriculography and equilibrium radionuclide angiography. The uncorrected radionuclide right ventricular volumes were calculated by normalizing background corrected end-diastolic and end-systolic counts from hand-drawn regions of interest obtained by phase analysis for cardiac cycles processed, frame rate, and blood sample counts. Attenuation correction was performed by a simple geometric method. The attenuation-corrected radionuclide right ventricular end-diastolic volumes correlated with the cineventriculographic end-diastolic volumes (r = .91, y = 3 + 0.92x, SEE = 27 ml). Similarly, the attenuation-corrected radionuclide right ventricular end-systolic volumes correlated with the cineventriculographic end-systolic volumes (r = .93, y = - 1 + 0.91x, SEE = 16 ml). Also, the mean attenuation-corrected radionuclide end-diastolic and end-systolic volumes were no different than the average cineventriculographic end-diastolic and end-systolic volumes (160 +/- 61 and 83 +/- 44 vs 170 +/- 61 and 86 +/- 43 ml, respectively). Comparison of the uncorrected and attenuation-corrected radionuclide right ventricular volumes demonstrated narrower 95% confidence intervals for the attentuation-corrected right ventricular volume determinations over a wide range of cineventriculographic volumes. Thus we conclude that: (1) attenuation-corrected radionuclide right ventricular end-diastolic and end-systolic volumes compare closely with those obtained by a cast-validated biplane cineventriculographic method and (2) attenuation-corrected radionuclide right ventricular volumes correspond more closely to determinations of biplane cineventriculographic right ventricular volumes and are thus likely to be more accurate than uncorrected radionuclide right ventricular volumes.

Adolescent↗
PubMed2003

Validity and representativity in the Danish Breast Cancer Cooperative Group--a study on protocol allocation and data validity from one county to a multi-centre database.

Population-based cancer registries collect basic information on incident cases, whereas clinical databases hold a broad range of variables that make them attractive sources in epidemiological research. Quality, completeness and representativeness of the clinical database in the Danish Breast Cancer Cooperative group (DBCG) were compared with those in a complete population-based database holding detailed information on patients with breast cancer. The study included 1765 patients diagnosed in Aarhus County between 1983 and 1989. Data on tumour characteristics were of high quality. Fifty percent of patients were included in DBCG trials and a total of 83% were notified in the DBCG register, the rest having significantly poorer stage distribution and survival probabilities. However, for patients younger than 70 years of age, the difference in overall survival between all patients and those notified in the DBCG register was only 2%. Follow-up was incomplete in patients treated outside the programme, and this had a major impact on recurrence-free survival. The DBCG database holds high-quality data, but as a population-based database, it is neither comprehensive nor representative.

Adult↗
PubMed1998

Device implementation, validation, and application assessment of two continuous 12-lead ECG monitors during percutaneous transluminal coronary angioplasty: description of the validation method and implications for clinical trials.

Comparability of clinical and research data sets may be undermined if the instruments used to acquire them vary. Even when standard 12-lead electrocardiographic formats are used for monitoring, proprietary signal processing techniques and sampling intervals may differ among devices. In order to directly compare the two commercially available standard 12-lead devices with monitoring capabilities, bifurcated wires from a single standard lead set were attached to each device in elective angioplasty patients. Neither device was used as a standard; rather, a method was designed to analyze the output from each device independently, and then, if results differed, data from both monitors were reviewed by consensus to determine the source of the differences. Analysis endpoints for each study included study quality, baseline ST-segment levels, the presence of ischemia, number of ischemic episodes, peak lead location, and peak lead amplitude. Sources of differences in these endpoints visible to consensus review included variations between devices in baseline stability, noise/artifact levels, stability of the QRS complex onset, and temporal sampling intervals.

Angioplasty, Balloon, Coronary↗
PubMed1989

Validation of an imaging system: steps to evaluate and validate a microscope imaging system for quantitative studies.

The processing methods described in this article are general and can be used with any computer with adequate software without reference to a specific experimental apparatus. To achieve appropriately corrected images, the operations must be performed correctly and in a specific order to extract meaningful information from digital images. The operations are subtraction of the dark current, a shading correction after low pass filtering of the shading mask, a geometric correction with a reference grid obtained at the longest wavelength of interest, and finally registration. Since the digital data sets are too large for manual evaluation, statistical criteria must be used to define the analytical capabilities and error limits of the system before the more interesting cellular studies can be undertaken.

Algorithms↗
PubMed1998

Preliminary validation of the MMPI-A for a male delinquent sample: an investigation of clinical correlates and discriminant validity.

Adolescent psychopathology, until recently, has been a largely neglected area of research and poses unique challenges for psychological assessments. In response to the specific need for adolescent-focused measures, the MMPI-A (Butcher et al., 1992) was among several measures to be developed. Although a sizeable literature exists on the original MMPI (Hathaway & McKinley, 1943) and adolescent populations, relatively few empirical studies have been published on the MMPI-A. The primary purpose of this study was the examination of clinical correlates for the MMPI-A for a male delinquent sample. MMPI-A protocols were collected from 99 adolescents at a North Texas juvenile correctional facility, and systematic comparisons were conducted between the Basic Scales and symptoms/diagnoses derived from the Schedule of Affective Disorders and Schizophrenia for School-Age Children (K-SADS-III-R; Ambrosini, Metz, Prabucki, & Lee, 1989). Using only K-SADS-III-R symptoms with high reliabilities (rs > .80), a comprehensive list of correlates was generated for the Clinical, Supplementary, and Content Scales. Additionally, stepwise discriminant functions successfully classified MMPI-A protocols according to K-SADS-III-R diagnoses. As an exploratory analysis, ethnic differences on MMPI-A profiles were also investigated, revealing significant differences among groups.

Adolescent↗