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Biomedical subjects

R S Thompson

Publications and source records attributed to R S Thompson.

At least 19 recordsLinked to original sources
PubMed1995

Primary and secondary prevention services in clinical practice. Twenty years' experience in development, implementation, and evaluation.

This article reviews lessons from 20 years of experience in development and provision of clinical preventive services at Group Health Cooperative of Puget Sound, a large health maintenance organization. Critical factors for enhancing service include the use of a population-based epidemiologic viewpoint coupled with specific evidence-based criteria to examine issues; involvement of practitioners in the process; a systems approach to implementation focused on predisposing factors of the practitioners and enabling factors in the practice, organizational, and community environments; feedback of program outcomes; and the use of automated clinical information systems. Outcome results from our clinical prevention efforts include a 32% decrease in late-stage breast cancer (1989 to 1990); 89% of 2-year-old children with complete immunizations (1994); decrease in adult smokers from 25% to 17% (1985 to 1994); and an increase in bicycle safety helmet use among children from 4% to 48% along with a 67% decrease in bicycle-related head injuries (1987 to 1992). Systematic population-based approaches to the development and provision of clinical preventive services targeting the one-to-one level of primary care and multiple infrastructure levels of care are forging a synthesis of clinical medicine and public health approaches. This approach will become pervasive as clinical information systems improve, risk information is captured routinely, and practitioners gain skills in the art of patient risk behavior change and population-based care.

Breast Neoplasms↗
PubMed1995

PSA screening: a public health dilemma.

Screening for prostate cancer with serum prostate specific antigen (PSA) is one of the most controversial practices in health care today and guidelines from professional and policy organizations are contradictory. Prostate cancer is unique because of a wide discrepancy between prevalent asymptomatic cancer and clinical disease and an uncertain natural history. Proponents and critics of mass screening agree that PSA can detect early cancer and that definitive data that PSA reduces prostat cancer mortality are not available. Differences in screening recommendations reflect distinct viewpoints regarding what constitutes screening benefit and what level of evidence is needed to endorse a screening practice. This review describes what is known about the areas most relevant to the conflicting perspectives: the epidemiology and natural history of prostate cancer, the ability of PSA to detect disease and operational characteristics of PSA as a screening test, and the efficacy of treatment of early disease.

Decision Making↗
PubMed1994

A population-based case-cohort evaluation of the efficacy of mammographic screening for breast cancer.

Screening efficacy may be evaluated in population-based, observational studies, provided one addresses biases that arise in nonrandomized screening evaluations. The authors evaluated the association of mammographic screening with breast cancer mortality among women without prevalent breast cancer. The cohort consisted of 94,656 women, aged > or = 40 years, enrolled in a large health maintenance organization in Washington State during the period 1982-1988. A case-cohort design limited chart abstraction of risk factor and screening information to 4% of the cohort. There were 1,144 incident breast cancer cases, including 126 who died of breast cancer during the study interval. An age-stratified proportional hazards analysis compared the screening experience of the breast cancer deaths with that of 2,237 controls. The family history of breast cancer, previous biopsy, and parity were included in the model to control for potential confounding effects of selection bias. With a mean follow-up of only 3.5 years postscreening, there was a small but statistically nonsignificant reduction in the risk of breast cancer mortality among women screened 1 year prior to diagnosis compared with unscreened women. The relative risk was 0.80 (95% confidence interval 0.34-1.85) for women aged > or = 40 years and 0.61 (95% confidence interval 0.23-1.62) for women aged > or = 50 years. This paper illustrates how case-cohort methodology can be used to perform efficient assessment of screening efficacy in large cohorts, while eliminating or controlling for sources of bias.

Adult↗
PubMed1994

Aortic Doppler velocity measurement and cardiac function in the fetal lamb.

Aortic haemodynamic parameters, and Doppler waveforms in particular, were investigated in acute experiments with fetal lambs. Cardiovascular changes were produced by central infusion of the drugs esmolol and dopamine. Pulsed Doppler waveforms were obtained from the descending thoracic aorta, simultaneous with recordings of pulsatile aortic volume flow rate, diameter and blood pressure. The relation between Doppler-derived velocities and the corresponding full vessel lumen velocities was shown to be fairly linear and consistent across different animals. The aortic volume flow per beat decreased with esmolol (p < 0.003, repeated measures ANOVA); the Doppler and vessel lumen mean velocities also decreased, whether measured only at peak systole or over the full cardiac cycle (at most p < 0.003). With dopamine the aortic flow per beat increased (p < 0.001), as did the Doppler and vessel lumen mean velocities (at most p < 0.02). An inverse relation between the aortic flow per beat and the peripheral resistance was observed. To identify inotropic changes in the presence of vascular effects, a theoretical model based on cardiac power output changes was implemented. The data were divided into three groups, according to whether the model did or did not identify a definite inotropic effect (positive or negative). The Doppler velocity changes for these three groups were different (p < 0.0001). The mean Doppler velocity increased by 7 cm s-1 in the positive inotropic effect group, and decreased by 4 cm s-1 in the negative group. The aortic flow parameters of the human fetus are very similar to those of the fetal lamb.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1994

Medical conditions and motor vehicle collision injuries in older adults.

OBJECTIVE: To determine whether medical conditions that can impair sensory, cognitive, or motor function increase the risk of injury due to motor vehicle collision in older drivers. DESIGN: Case-control study. SETTING: Group Health Cooperative of Puget Sound, a large prepaid health plan. PARTICIPANTS: Group Health members age 65 or older who were licensed drivers in 5 counties. Cases were injured while driving during 1987 or 1988. Controls were matched to cases on age, gender, and county of residence but experienced no such injury during the study years. MEASUREMENTS: The outcome was injury requiring medical care due to a police-investigated motor vehicle collision. Risk factors evaluated included selected medical conditions active within the previous 3 years, as determined from the medical record. MAIN RESULTS: Injury risk was 2.6-fold higher in older diabetic drivers (95% CI: 1.4-4.7), especially those treated with insulin (odds ratio [OR] = 5.8, 95% CI: 1.2-28.7) or oral hypoglycemic agents (OR = 3.1, 95% CI: 0.9-11.0), those with diabetes for over 5 years (OR = 3.9, 95% CI: 1.7-8.7), and those with both diabetes and coronary heart disease (OR = 8.0, 95% CI: 1.7-37.7). Increases were also found for older drivers with coronary artery disease (OR = 1.4), depression (OR = 1.7), alcohol abuse (OR = 2.1), or falls (OR = 1.4), but these associations could easily have arisen by chance. CONCLUSIONS: Counseling about driving risks may be warranted for certain elderly diabetic drivers. Further research is needed to determine whether transient hypoglycemia or long-term complications explain these effects.

Accidents, Traffic↗
PubMed1992

Measurement of severity for nonhospitalized injuries in the pediatric age group.

To better classify minor injuries in the pediatric outpatient population, we empirically developed a scale to predict functional impairment, one week and one month postinjury, based on data available at the time of care. A sample of 857 injured children aged five to 19 years was randomly split into two subsamples. Using logistic regression techniques, predictive models were developed and confirmed on the subsamples and then applied to the full sample. Age, location of injury, and type of injury were predictive of impairment one week post-injury; however, type of injury was the only consistently significant predictor. Type of injury, specifically fracture, dislocation, and sprain, and location of injury (lower extremity) were significant predictors of functional impairment one month postinjury; however, once again, the type of injury was the only variable consistently significant across all models. Other than the type of injury, the variables available at the time of care were too uniform between disabled and nondisabled patients to be useful in developing a severity scale for minor injuries. We conclude that other outcome measurements or scale development techniques should be explored to develop a useful classification scheme for minor injuries.

Adolescent↗
PubMed1992

Calculation of Doppler spectral power density functions.

A volume integral method for the calculation of Doppler ultrasound spectral power density (spd) functions is described. Axisymmetric flow in a circular tube with a power law velocity profile is assumed. The spd function is regarded as a probability density function for scatterer velocity, and the assumptions under which this is justified are considered. It is shown that the spd function is independent of Doppler angle except in the presence of wall reflection effects. A coordinate system centered on the beam is used and this enables the integrals to be easily formulated for arbitrary beams. Irregularly shaped and nonuniform beams can be treated. For the common flow and beam patterns, which exhibit symmetry, the volume integrals can often be reduced to a single integral and evaluated directly. The method is applied and the spectra are calculated for various different cases. Results are obtained for uniform rectangular and circular insonating beams, and for nonuniform beams with Gaussian, jinc, and sinc profiles. The effects of narrow beams and wall reflection are shown. The method may be readily applied to other beam and flow patterns, and extension to more complicated situations is also discussed.

Blood Flow Velocity↗
PubMed1991

Development of an immunization tracking system in a large health maintenance organization. Group Health Cooperative of Puget Sound.

We have successfully developed a mainframe system for tracking all immunizations administered to enrollees in a large HMO. This system will provide comprehensive immunization records on a population of over 350,000 patients. Data required by the National Childhood Vaccine Injury Act of 1986 are locally entered into terminals, and records of immunization are stored in a database. Preliminary results show that data entry times are practical, but that improvement in data quality is needed. This immunization tracking system will be used for research, and as the foundation of an immunization reminder system under development.

Health Maintenance Organizations↗
PubMed1991

Injuries to children and adolescents: impact on physical health.

Disability resulting from injuries was examined in a health maintenance organization population of children and adolescents 0 through 19 years of age. The physical health status instrument from the Rand Health Insurance Study was used to evaluate functional outcome of patients seen in the emergency room and outpatient clinic. Overall, 55.1% of individuals had limitations in their usual activities during the week following injury; 16.4% and 3.8% were not yet back to full activities after 1 week and 1 month, respectively. Individuals 10 years of age and older had more functional impairment than did younger children. Restrictions were greatest for fractures/dislocations and sprains and for injuries due to sports, play/recreational activities, and falls.

Activities of Daily Living↗
PubMed1990

Revisions in the risk-based Breast Cancer Screening Program at Group Health Cooperative.

To pursue the goal of achieving regular use of mammography in women 40 years of age and older, a risk-based selective approach to screening was implemented at a 400,000-member managed health care system in the Northwest in 1985. This article describes the context for this approach to selective screening and reviews revisions in the algorithm used to determine when and how a woman should be screened. Changes made in 1988 with respect to age criteria, intervals for mammography, and which risk factors to include are discussed. The result of these changes is that 83% of women 40 years of age and older are now eligible for regular mammography compared with 57% under the former system. The total use of mammography in any given year remains unchanged. The results of this analysis have implications for other organizations attempting to promote the use of mammography.

Adult↗
PubMed1990

Feasibility of a randomized trial of a low-fat diet for the prevention of breast cancer: dietary compliance in the Women's Health Trial Vanguard Study.

The Women's Health Trial Vanguard Study was conducted to examine the feasibility of a nationwide, randomized multicenter intervention trial to test the hypothesis that a low-fat diet followed for a period of 10 years will reduce breast cancer risk. Women ages 45-69 years at increased risk of breast cancer were randomized into intervention (low-fat diet, n = 184) and control (usual diet, n = 119) groups. On the basis of 4-day food records, baseline fat intakes were comparable in the two groups, averaging 1,718 kcal with 39% of energy as fat. Intervention women reported substantially lower fat intake at 6 (20.9% kcal), 12 (21.6%), and 24 months (22.6% kcal). In contrast, control women reported only slight reductions in fat intake (37.3% kcal at 12 months and 36.8% kcal at 24 months). Evidence that these women were indeed complying with the low-fat dietary intervention comes from (a) the reasonable nature of reported nutrient changes within food groups in the intervention women and (b) agreement between observed and expected differences in plasma total cholesterol between the control and the intervention groups. At 12 months, the observed control - intervention plasma cholesterol difference was 13.1 +/- 4.6 mg/dl while the expected difference based on the Keys equation was 15.1 +/- 1.1 mg/dl; at 24 months, the observed difference was 15.5 +/- 4.3 mg/dl and the expected difference was 12.0 +/- 1.2 mg/dl. These analyses indicate that the intervention women made substantial dietary changes and have successfully maintained these changes over a 2-year period. This study thus demonstrates the feasibility of a randomized trial with an intensive low-fat dietary intervention.

Aged↗
PubMed1990

Doppler waveform pulsatility index and resistance, pressure and flow in the umbilical placental circulation: an investigation using a mathematical model.

A mathematical model of the umbilical placental circulation was used to examine the effect of different physiological variables on the pulsatility index (PI) of the umbilical artery Doppler waveform. The variables include the umbilical and placental resistances, the volume flow rate and the pressure. In the model the branching structure of the placental villous tree is considered in detail, while each arterial branch is itself represented simply using a resistor and a capacitor. Placental vascular disease is modelled as obliteration of a fraction of the terminal branches of the tree. The model umbilical artery PI depends on the ratio of the placental resistance to the umbilical artery resistance. The PI increases with vascular disease, but the rate of increase is not uniform. Initially, the placental resistance and the PI increase very slowly with vessel obliteration. Once the level of vessel obliteration has reached a large enough value--typically between 60% and 90% obliteration--the PI begins to rise sharply. A larger placental vascular bed can accommodate a greater level of vessel obliteration before this rapid PI rise begins. The umbilical artery PI also depends on the pulsatility of the input (aortic bifurcation) pressure waveform, but blood pressure variations in the physically attainable range cannot account for the very high PI values associated with fetal compromise. Physically attainable pressure waveform changes would, however, enable the fetus with substantial placental vascular disease to maintain umbilical volume flow rate, and at the same time exhibit a raised umbilical artery PI value.

Blood Flow Velocity↗
PubMed1990

Incidence of bicycle-related injuries in a defined population.

Population-based incidence rates for head injuries and total injuries resulting from bicycle crashes were calculated in a Seattle, Washington health maintenance organization population. Overall rates were 163 per 100,000 for all injuries and 42/100,000 for head injuries. Individuals between 5 and 14 years of age are at highest risk for bicycle-related injuries. The data are presented for their potential utility in program planning.

Age Factors↗
PubMed1990

A case-control study of the effectiveness of bicycle safety helmets in preventing facial injury.

In a case-control study we sought to assess the potential effectiveness of helmets in preventing facial injuries. Our study included 212 bicyclists with facial injuries and 319 controls with injuries to other body areas, who were treated in emergency rooms of five Seattle area hospitals over a one-year period. Using regression analyses to control for age, sex, education and income, accident severity, and cycling experience we found no definite effect of helmets on the risk of serious facial injury (odds ratio 0.81; 95 percent confidence interval = 0.45, 1.5), but protection against serious injuries to the upper face (odds ratio 0.27; 95% CI = 0.1, 0.8). No protection was found against serious injuries to the lower face. The independent effect of helmet use on facial injury was difficult to isolate due to the association of head and facial injuries. Our results suggest that bicycle helmets as presently designed may have some protective effect against serious upper facial injuries.

Adolescent↗