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Biomedical subjects

Ke Tom Xu

Publications and source records attributed to Ke Tom Xu.

11 recordsLinked to original sources
PubMed2006

State-level variations in income-related inequality in health and health achievement in the US.

The objective of this study was to examine state-level variations in income-related inequality in health and overall health achievement in the US. Data that were representative of the US and each state in 2001 were extracted from the Current Population Survey 2001. Income-related inequality in health and health achievement were measured by Health Concentration and Health Achievement Indices, respectively. Significant variations were found across states in income-related inequality in health and health achievement. In particular, states in the south and east regions, on average, experienced a higher degree of health inequality and lower health achievement. About 80% of the state-level variation in health achievement could be explained by demographics, economic structure and performance, and state and local government spending and burden. In contrast, medical care resource indicators were not found to contribute to health achievement in states. States with better health achievement were more urbanized, had lower proportions of minority groups, females and the elderly, fewer individuals below the poverty line, larger primary industry, and lower unemployment rates. Also, per capita state and local government spending, particularly the proportion spent on public health, was positively associated with better health achievement. Because of the direct implications of health level and distribution in resource allocation and social norms, states with a lower level of health achievement need to prioritize efforts in increasing and reallocating resources to diminish health inequality and to improve population health.

Financing, Government↗
PubMed2005

Patient involvement in medical decision-making and pain among elders: physician or patient-driven?

BACKGROUND: Pain is highly prevalent among older adults, but little is known about how patient involvement in medical decision-making may play a role in limiting its occurrence or severity. The purpose of this study was to evaluate whether physician-driven and patient-driven participation in decision-making were associated with the odds of frequent and severe pain. METHODS: A cross-sectional population-based survey of 3,135 persons age 65 and older was conducted in the 108-county region comprising West Texas. The survey included self-reports of frequent pain and, among those with frequent pain, the severity of pain. RESULTS: Findings from multivariate logistic regression analyses showed that higher patient-driven participation in decision-making was associated with lower odds (OR, 0.82; 95% CI, 0.75-0.89) of frequent pain, but was not significantly associated with severe pain. Physician-driven participation was not significantly associated with frequent or severe pain. CONCLUSIONS: The findings suggest that patients may need to initiate involvement in medical decision-making to reduce their chances of experiencing frequent pain. Changes to other modifiable health care characteristics, including access to a personal doctor and health insurance coverage, may be more conducive to limiting the risk of severe pain.

Aged↗
PubMed2005

Visual field changes after laser in situ keratomileusis.

PURPOSE: To determine whether laser in situ keratomileusis (LASIK) affects the central 30-degree visual field. SETTING: University-based ophthalmology practice. METHODS: This nonrandomized clinical trial comprised 14 normal patients (27 eyes) scheduled to have LASIK for myopia or myopic astigmatism. Automated static perimetry was performed before and 6 months after surgery using the Octopus 1-2-3 perimeter and the Dynamic-32 test strategy. Patient data included sex, age, preoperative and postoperative refractive errors, preoperative and postoperative best corrected visual acuity, preoperative corneal thickness, programmed optical zone, programmed total ablation diameter, and duration of microkeratome suction. All surgery was performed using the same Alcon LADARVision 4000 excimer laser. The main outcome measures were the mean sensitivity (MS) change in the central 15-degree visual field and the MS change in the 15- to 30-degree visual field. A multivariate analysis of the MS change as a function of preoperative clinical parameters was performed. RESULTS: There was no significant change in the MS in the central 15-degree visual field; between 15 and 30 degrees, there was a statistically significant decrease of -0.82 dB +/- 1.40 (SD) (P=.01, 2-tailed t test). The decline in MS was positively correlated with refractive error and corneal thickness; it was negatively correlated with the programmed optical zone diameter. CONCLUSIONS: Automatic static perimetry can detect decreased sensitivity in the midperipheral visual field after myopic LASIK. It may be a useful quantitative subjective test for measuring the effects of future improvements in surgical technique on vision quality.

Adult↗
PubMed2005

Six-month variability of the dark-adapted pupil diameter.

PURPOSE: To determine the individual variability of the dark-adapted pupil diameter over 6 months using a standardized dark-adaptation protocol. SETTING: Texas Tech University Health Sciences Center, Lubbock, Texas, USA. METHODS: This prospective observational cohort study comprised volunteers with no history of ocular disease, surgery, or injury other than requirement for refractive correction. The right eye was tested. A standardized dark-adaptation protocol was used that controlled for accommodation and patient alertness. Infrared, still digital photographs were taken after 10 minutes of dark adaptation at 1 lux and were analyzed using digital image software. Testing was performed at baseline in the afternoon, at 3 months in the afternoon, and at 6 months in the morning. Lifestyle factors such as diet and exercise were not controlled. RESULTS: Mean intersession differences were 0.04 mm (95% confidence interval [CI]: -0.68-0.146), 0.15 mm (95% CI: -0.001-0.297), and 0.09 mm (95% CI: -0.048-0.236) for baseline-3 month, baseline-6 month, and 3 month-6 month comparisons, respectively. None of these differences was significantly different from zero (P>.05, 2-tailed Student t tests). The likelihood that the mean intersession difference was >.25 mm was negligible for all comparisons (P=.9996, .9099, and .9829 respectively, 1-tailed Student t tests). CONCLUSION: When a consistent dark-adaptation protocol that controls for alertness and accommodation is used, normal young individuals showed no significant variation in the dark-adapted pupil diameter over a 6-month period.

Accommodation, Ocular↗
PubMed2005

Comparison of Colvard pupillometer and infrared digital photography for measurement of the dark-adapted pupil diameter.

PURPOSE: To investigate the accuracy of pupil diameter measurement using the Colvard pupillometer and to determine the learning curve for inexperienced examiners. SETTING: Texas Tech University Health Sciences Center, Lubbock, Texas, USA. METHODS: In this population study, subjects with normal pupillary behavior were tested by 1 of 2 investigators (examiner A, examiner B). After 5 minutes of dark adaptation at 1 lux, digital infrared pupil photography of the right eye was performed, followed by measurement of the horizontal pupil diameter and vertical pupil diameter with the Colvard pupillometer. The photographs were digitally analyzed to determine the horizontal and vertical pupil diameters. During phase I of the study, examiners were masked to the results of infrared pupil photography; during phase II, they reviewed the infrared pupil photography results after each testing session. Bland-Altman plots were created to detect measurement bias; results were graphed by subject test sequence to assess learning. A test difference of less than +/-0.5 mm was considered clinically acceptable. RESULTS: Fifty-nine subjects were tested in phase I, of whom 39 had adequate infrared pupil photography for analysis; 40 were tested in phase II, of whom 34 were included. The mean age of the analyzed subjects was 27 years (range 18 to 44 years). For all subjects, the infrared pupil photography median horizontal pupil diameter was 7.09 mm +/- 0.75 (SD) (range 5.44 to 8.79 mm); the median vertical pupil diameter was 7.22 +/- 0.79 mm (range 5.45 to 9.10 mm). Examiner A initially had a negative bias (Colvard pupillometer value less than infrared pupil photography value) for both horizontal and vertical pupil diameter measurements, which resolved during phase I after 23 subjects were tested; 18 of the final 19 subjects tested (11 phase I, 8 phase II) showed a test difference of less than 0.5 mm for all readings. The pupil diameter did not affect the bias. Examiner B had a strong positive bias that persisted throughout the study. Testing 26 subjects in 5 sessions during phase II did not improve the accuracy. During the final testing session, 3 of 8 subjects had a test difference of 0.5 mm or more in at least 1 dimension. The pupil diameter did not affect the bias. CONCLUSION: The Colvard pupillometer is susceptible to user errors causing unidirectional bias and seems to have a steep and variable learning curve.

Adolescent↗
PubMed2004

Day to day variability of the dark-adapted pupil diameter.

PURPOSE: To determine the individual variability of the dark-adapted pupil diameter over 2 testing sessions using a standardized dark-adaptation protocol. SETTING: Texas Tech University Health Sciences Center, Lubbock, Texas, USA. METHODS: In this prospective observational cohort study, 40 volunteers with no history of ocular disease, surgery, or injury other than requirement for refractive correction were included. The right eye was tested. A standardized dark-adaptation protocol was used that controlled for accommodation and patient alertness. Infrared, still digital photographs were taken after 5 and 10 minutes of dark adaptation and analyzed independently by 2 investigators using digital-image software. Two test sessions were performed 1 to 7 days apart. Lifestyle factors such as sleep, diet, and exercise were not controlled. RESULTS: The mean subject age was 31.5 years (range 20 to 49 years). There were 20 men; 27 subjects wore correction for myopia, and 13 wore no correction. The mean interval between test sessions was 2 days (range 1 to 7 days). The mean difference and 95% confidence intervals for pupil diameter difference between sessions were as follows: 5-minute readings, +0.032 mm (-0.030 to +0.094); 10-minute readings, -0.006 mm (-0.059 to +0.047); mean of 5- and 10-minute readings, +0.013 mm (-0.038 to +0.064). Using the paired t test, the pupil diameter did not differ significantly between sessions in 5-minute dark adaptation (P =.2980), 10-minute dark adaptation (P =.8263), or the mean (P =.6049). CONCLUSION: Using a consistent dark-adaptation protocol that controlled for alertness, individuals aged 20 to 49 years showed no significant variation in dark-adapted pupil diameter when tested twice in 1 week.

Accommodation, Ocular↗
PubMed2004

Normal values for a clinical test of letter-recognition contrast thresholds.

PURPOSE: To investigate the contrast thresholds (CTs) in normal subjects using a high-luminance, letter-recognition task under clinically relevant testing conditions. SETTING: Texas Tech University Health Sciences System, Lubbock, Texas, USA. METHODS: Sixty normal subjects aged 20 to 49 years with a best corrected visual acuity of 20/20 or better in both eyes participated. M & S Technologies software was used to display black-on-white Sloan letters at contrast levels of 25%, 20%, 15%, 12%, and 10% through 1% in 1% decrements. The effects of age, sex, optotype size, eye dominance, ambient illumination level (bright = 625 - 630 lux; dim = <3 lux), and direction of approach to threshold were analyzed using a multivariate, ordinary, least-squares analysis. RESULTS: Age and sex did not influence CTs. Ascending versus descending testing was not statistically significant (P>.5). The effects of room illumination and eye dominance were significant (P<.01). Significant differences were found between 20/30 and 20/50, 20/30 and 20/70, and 20/50 and 20/70 optotype sizes (P<.01 for all comparisons). CONCLUSIONS: A commercially available, computer-based test of CTs was easy to administer and apparently easy for inexperienced subjects to perform. The results suggest criteria for detecting visual problems concerned with familiar but complex spatial-image shapes. This information might be used to assess the effects of treatments such as laser refractive surgery on recognition contrast. Further study is warranted.

Adult↗
PubMed2004

Parents' reports of children's medical care access: are there Mexican-American versus non-Hispanic white disparities?

OBJECTIVES: We investigated whether there were Mexican-American versus non-Hispanic white disparities in parents' reports of problems with 4 dimensions of children's medical care access after controlling for a range of demographic, social, economic, and health status factors. METHODS: Data were collected through a telephone survey of 5941 parents residing in Texas. The survey questionnaire included measures of the parent's demographic and socioeconomic status and the child's health-related quality of life. The behavioral model was used to guide the inclusion of factors in multivariate logistic regression analyses of parents' reports of their children's ability to obtain an appointment for routine/regular care, obtain care for illness/injury, obtain help/advice over the phone when calling the doctor's office, and having to wait more than 15 minutes in the doctor's office. RESULTS: Mexican-American parents had worse reports of all 4 dimensions of their children's access even after controlling for predisposing, enabling, and need factors. Among Mexican-Americans, there were no differences between those who primarily spoke English versus Spanish. Other factors that were significantly associated with at least 2 reports of access were household income, the child's insurance status, and the child's health-related quality of life. CONCLUSIONS: Mexican-American children face problems accessing medical care in a timely manner that are not fully explained by parents' demographic, social, and economic status or children's health-related quality of life. Health policy makers, managers, and clinicians should further consider how they could reduce the inequity of access to medical services among Mexican-American children.

Adolescent↗
PubMed2004

Factors associated with health-related quality of life among an older population in a largely rural western region.

CONTEXT: As elderly people become a larger proportion of the rural population, it is important to identify those at risk for poor health. Predictors of health-related quality of life can be useful in designing interventions. PURPOSE: One objective of the present study was to profile the health-related quality of life of community-dwelling, elderly people in a southwestern region of the United States. A related objective was to identify the principal factors associated with health-related quality of life, thereby identifying population subgroups in greatest need of health or social services. METHODS: A telephone survey of approximately 5,000 individuals 65 years and older collected data on need for assistance with activities of daily living, physical and mental health-related quality of life, and worry about health status measures. A modified version of the Behavioral Model was used to more clearly distinguish the different groups at risk for poor health. FINDINGS: Those groups of community-dwelling, elderly people in the poorest health were older than 75 years, had less than a high school education, were retired or unemployed, and had low household income. No differences were found by urban, rural, and frontier residence. CONCLUSIONS: To maintain the physical, social, and psychological health of older people residing in rural and urban areas, social services, medical care, and supportive services are needed, particularly among the most socially and economically disadvantaged.

Activities of Daily Living↗
PubMed2002

Are rural residents and Hispanics less satisfied with medical care? Evidence from the Permian Basin.

Few population-based studies of consumers' perceptions of health care quality have included both rural residents and Hispanics. Using data collected through a random-digit telephone survey of households in the Permian Basin region of west Texas, an area with a relatively high percentage of Mexican Americans, we tested for rural/urban and ethnic differences in satisfaction with medical care. The study had several limitations, but the findings suggest that rural residents of this region rate the quality of their medical care overall more negatively than do their urban counterparts. No ethnic differences were found when controlling for demographic, social, economic, and health-status characteristics. Other factors, including part-time employment, a lack of continuous health insurance coverage, and poor health status appear to have a stronger, negative relationship with satisfaction. The collection and reporting of more specific measures of interpersonal and technical quality would further enable policy-makers, managers, and clinicians to better serve their patient populations.

Adult↗