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PubMed2002

Bias adjustment in analysing longitudinal data with informative missingness.

The recent biostatistical literature contains a number of methods for handling the bias caused by 'informative censoring', which refers to drop-out from a longitudinal study after a number of visits scheduled at predetermined intervals. The same or related methods can be extended to situations where the missing pattern is intermittent. The pattern of missingness is often assumed to be related to the outcome through random effects which represent unmeasured individual characteristics such as health awareness. To date there is only limited experience with applying the methods for informative censoring in practice, mostly because of complicated modelling and difficult computations. In this paper, we propose an estimation method based on grouping the data. The proposed estimator is asymptotically unbiased in various situations under informative missingness. Several existing methods are reviewed and compared in simulation studies. We apply the methods to data from the Wisconsin Diabetes Registry Project, a longitudinal study tracking glycaemic control and acute and chronic complications from the diagnosis of type I diabetes.

Bias↗
PubMed1979

1977 National survey of support in space and dollars for departments of obstetrics and gynecology from their medical schools.

A questionnaire was sent to all chairpersons in obstetrics and gynecology departments in United States Medical Schools in the fall of 1977 seeking information on the school's support of that department for the year 1977 in terms of space and dollar commitments. A total of 113 schools were contacted; 106 responded (93.8%) and the data were tabulated. There were no significant differences between the private and state school resources. The average space commitment was 9,277 +/- SEM 709 square feet and the average school budget was 441,023 +/- SEM 24,265 dollars/year. These data were adjusted for class size and provide the first data base for assessing the adequacy of a medical school's commitment to a department of obstetrics and gynecology.

Costs and Cost Analysis↗
PubMed2003

Impact of obesity in the setting of high-dose chemotherapy.

Obesity is a common and increasing problem affecting the developed world. Chemotherapy pharmacokinetics in the context of obesity demonstrate prolonged elimination time for several agents, but there is no consensus regarding optimal dosing schemes. Retrospective studies suggest differences in toxicity for obese adult patients but these data may be greatly impacted by chemotherapy dose adjustments. Outcome data from several studies have suggested that obese adult patients suffer poorer disease-free survival and overall survival, although this is not a uniform conclusion in all studies. Prospective studies of chemotherapy pharmacokinetics are needed to address the issue of optimal chemotherapy dosing in the obese population.

Adult↗
PubMedDate not supplied

Changing pressure-redistributing mattress stocks: costs and outcomes.

There remains considerable confusion regarding the selection of appropriate pressure-redistributing support surfaces, although it is accepted that use of low-pressure foam mattresses is likely to reduce the incidence of pressure ulcers compared with standard hospital mattresses. In this study, a 650- hospital replaced its mattress stock with low-pressure foam mattresses with over pounds sterling 100 000 cost savings in the first year after implementation. Incidence and prevalence data were recorded but given the challenges of interpreting apparent trends in the data (due to the lack of robust data collection methodologies and no case-mix adjustment) these data were not included.

Beds↗
PubMed2006

Resonance of sputum spigot with air vibration.

A mathematical model calculation has been presented on the resonant frequency of the oscillating sputum spigot in a cylindrical pipe, with which we investigated similar phenomena in bronchial tubes. We confirmed the theoretical results by two types of experiments using pseudo-sputum (5 and 10% solutions of mucin) spigots instead of a human pulmonary one, and found the model was suitable for estimating the effects of clinical vibrational treatments expectorating sputum spigots plugged in small bronchi. The main points of the paper are summarized as follows. 1. The validity of the fluid model used was verified using reported experimental data of Litt and co-workers. After adjusting their data in a Casson plot, Casson fluidity was found to be the best parameter to represent viscosity of the sputum. 2. A theoretical investigation on the vibrational sputum spigots in narrow tubes was done using an analytical model calculation. From the resultant formula, which expresses the resonant frequency of the oscillation of the spigot with its physical values (the radius of the airway, the length of the spigot, the elasticity of the sputum, and the surface tension), many points became clear; for example, the resonant frequency of sputum spigot vibration in a narrow bronchial tube is too high to propagate there under the effective influence of surface tension. 3. Two experiments were performed with pseudo-sputum (5 and 10% solutions of mucin) instead of a human pulmonary one. After substituting the resonant frequencies of the pseudo-sputum spigot vibration in our tube experiment into the resultant formula derived from our analytical model calculation we estimated the elasticity values, which agreed with those from our plate experiment. The validity of our theory was strongly supported by this agreement.

Elasticity↗
PubMed2003

Automated assessment of the composition of breast tissue revealed on tissue-thickness-corrected mammography.

OBJECTIVE: Variations in the thickness of a compressed breast and the resulting variations in mammographic densities confound current automated procedures for estimating tissue composition of breasts from digitized mammograms. We sought to determine whether adjusting mammographic data for tissue thickness before estimating tissue composition could improve the accuracy of the tissue estimates. MATERIALS AND METHODS: We developed methods for locally estimating breast thickness from mammograms and then adjusting pixel values so that the values correlated with the tissue composition over the breast area. In our technique, the pixel values are corrected for the nonlinearity of the combined characteristic curve from the film and film digitizer; the approximate relative thickness as a function of distance from the skin line is measured; and the pixel values are adjusted to reflect their distance from the skin line. To estimate tissue composition, we created a backpropagation neural network classifier from features extracted from the histogram of pixel values, after the data had been adjusted for characteristic curve and tissue thickness. We used a 10-fold cross-validation method to evaluate the neural network. The averaged scores of three radiologists were our gold standard. RESULTS: The performance of the neural network was calculated as the percentage of correct classifications of images that were or were not corrected to reflect tissue thickness. With its parameters derived from the pixel-value histogram, the neural network based on corrected images performed better (71% accuracy) than that based on uncorrected images (67% accuracy) (p < 0.05). CONCLUSION: Our results show that adjusting tissue thickness before estimating tissue composition improved the performance of our estimation procedure in reproducing the tissue composition values determined by radiologists.

Aged↗
PubMed1995

Feasibility of monitoring patient based health outcomes in a routine hospital setting.

OBJECTIVE: To assess the feasibility of monitoring health outcomes in a routine hospital setting and the value of feedback of outcomes data to clinicians by using the SF 36 health survey questionnaire. DESIGN: Administration of the questionnaire at baseline and three months, with analysis and interpretation of health status data after adjustments for sociodemographic variables and in conjunction with clinical data. Exploration of usefulness of outcomes data to clinicians through feedback discussion sessions and by an evaluation questionnaire. SETTING: One gastroenterology outpatient department in Aberdeen Royal Hospitals Trust, Scotland. PATIENTS: All (573) patients attending the department during one month (April 1993). MAIN MEASURES: Ability to obtain patient based outcomes data and requisite clinical information and feed it back to the clinicians in a useful and accessible form. RESULTS: Questionnaires were completed by 542 (95%) patients at baseline and 450 (87%) patients at follow up. Baseline health status data and health outcomes data for the eight different aspects of health were analysed for individual patients, key groups of patients, and the total recruited patient population. Significant differences were shown between patients and the general population and between different groups of patients, and in health status over time. After adjustment for differences in sociodemography and main diagnosis patients with particularly poor scores were identified and discussed. Clinicians judged that this type of assessment could be useful for individual patients if the results were available at the time of consultation or for a well defined group of patients if used as part of a clinical trial. CONCLUSIONS: Monitoring routine outcomes is feasible and instruments to achieve this, such as the SF 36 questionnaire, have potential value in an outpatient setting. IMPLICATIONS: If data on outcomes are to provide a basis for clinical and managerial decision making, information systems will be required to collect, analyse, interpret, and feed it back regularly and in good time.

Adolescent↗
PubMed1991

Sleep and dreaming in Holocaust survivors. Dramatic decrease in dream recall in well-adjusted survivors.

Sleep data were obtained on 12 well-adjusted and 11 less-adjusted Holocaust survivors and on 10 control subjects. Each was also awakened from rapid eye movement sleep for dream recall. The less-adjusted survivors had more prolonged sleep latency than the well-adjusted and the control groups and lower sleep efficiency than the control subjects. The well-adjusted group had a significantly lower dream recall rate (33.7%) than the less-adjusted (50.5%) and control groups (80%). There were also significant between-groups differences in dream structure and dream content, in the direction of less complex and less salient dreams in the well-adjusted survivors. It is suggested that the decrease in dream recall is one of the forms of long-term adjustment to severe traumatic events.

Adaptation, Psychological↗
PubMed2000

The real and the nominal? Making inflationary adjustments to cost and other economic data.

Given the scarcity of cost data for health interventions, there has been substantial use of a relatively small number of existing studies to underpin policy development formulation. Intervention-specific cost and cost-effectiveness data have been used to plan overall budgets, to assess the relative efficiency of different interventions and to consider the resource requirements for programme implementation at both the local and national levels. Cost and cost-effectiveness comparisons have been made between these studies and general sources such as the World Bank's World Development Report 1993. At the same time, information on key health sector variables, such as annual health expenditures, has been systematically compiled for more than two decades. The question of possible inflationary effects is becoming increasingly important as the original data on which these numbers are based ages. For example, cost figures from the mid-1980s require a 60% inflationary adjustment simply to maintain their real value in current dollars. This paper looks at methods to adjust cost data to account for inflation and discusses the difference between real or constant and nominal or current values. These methods are also used to make inflationary adjustments to other types of economic data such as income.

Cost-Benefit Analysis↗
PubMed2003

Using clinical outcomes to identify expert physical therapists.

BACKGROUND AND PURPOSE: Previous studies of expert physical therapists have sampled therapists based on years of clinical experience or reputation, not on their patients' clinical outcomes. The purposes of this study were to identify expert physical therapists by using patient self-reported outcomes and to describe the characteristics of clinicians whose patients with lumbar spine syndromes reported higher health-related quality of life (HRQL) following rehabilitation. METHODS: Retrospective data were analyzed on 24276 patients (mean age=47.8 years, SD=16, range=14-97) with lumbar spine syndromes treated by 930 physical therapists participating in the Focus On Therapeutic Outcomes database in 1999-2000. Physical therapists and staff answered questions concerning years of experience and practice setting when starting their participation in the outcomes system. Patient self-report HRQL data were collected at intake and discharge from outpatient rehabilitation. Discharge HRQL data were risk adjusted using patient characteristics. Data were aggregated by physical therapist. Risk-adjusted discharge HRQL scores were used to classify physical therapists whose patients reported mean HRQL improvement above the 90th percentile as experts and physical therapists whose patients reported mean HRQL improvement between the 45th and 55th percentiles as average. RESULTS: Therapists classified as expert had fewer patients in the database than did therapists classified as average (mean SD) (19 +/-17 versus 29 +/-22). Mean treatment duration was different between groups (32 +/- 11 days for the expert group versus 31+/-8 days for the average group). DISCUSSION AND CONCLUSION: The results challenge assumptions that extensive clinical experience is necessary to achieve superior patient outcomes, and they provide information about the relationship between therapist characteristics and patient outcomes.

Adolescent↗
PubMed2005

[Overweight and obesity in Germany 1984-2003].

The magnitude and the development of the prevalence of overweight and obesity in Germany during the past 20 years are analysed in this contribution. Using body mass index (BMI) data of the National Examination Surveys (1984-1992), the German National Health Interview and Examination Survey 1998 as well as the Telephone Health Survey 2003, all representative of the adult non-institutionalised population, the occurrence of overweight and obesity is studied. To improve the comparability with measurement values, the Telephone Health Survey data which were based on self-reporting were adjusted. All data were weighted to improve the representativeness for the time of assessment. Although the proportion of persons with a BMI between 25 and 30 did not change essentially during the last 20 years, the proportion of obese individuals (BMI>or=30) increased considerably. At present, about 70% of men and 50% of women in Germany are overweight or obese. In conclusion, the prevalence of overweight and obesity in Germany continues to increase.

Adult↗