Search PubMed⌕ Search

Biomedical subjects

S L Hui

Publications and source records attributed to S L Hui.

17 recordsLinked to original sources
PubMed1991

Role of physical activity in the development of skeletal mass in children.

A group of 118 children, aged 5.3-14 years, were enrolled in a prospective study of calcium supplementation and bone mass. At entry to the study, questionnaires regarding the child's usual physical activity were administered to the children and their mothers. Repeated activity assessments at 6 month intervals indicated good within-person agreement for total activity and for most individual activities. Consistent positive associations were observed between bone mineral densities (BMD) in the radius, spine, and hip and most activities. A summary measure (total hours of weight-bearing activity) was significantly related to BMD in the radius and hip, independently of age or gender effects. Self-reported sports and play activities were associated with BMD, but neither time spent watching television nor hours of physical education classes were associated either positively or negatively with skeletal mass. These data suggest that important increments in skeletal mass may result from physical activity during childhood.

Adolescent↗
PubMed1991

Validation techniques for logistic regression models.

This paper presents a comprehensive approach to the validation of logistic prediction models. It reviews measures of overall goodness-of-fit, and indices of calibration and refinement. Using a model-based approach developed by Cox, we adapt logistic regression diagnostic techniques for use in model validation. This allows identification of problematic predictor variables in the prediction model as well as influential observations in the validation data that adversely affect the fit of the model. In appropriate situations, recommendations are made for correction of models that provide poor fit.

Benzothiadiazines↗
PubMed1991

Practice randomization and clinical research. The Indiana experience.

Thoughtful preparation of a research laboratory is an early step in designing a program for scientific investigation. The Division of General Internal Medicine at Indiana University has maintained a "laboratory" for outpatient clinical investigation for more than 15 years. In this report, we describe the structure and function of the General Medicine Practice in the Regenstrief Health Center on the campus of the Indiana University School of Medicine in Indianapolis. Specifically, we discuss the ongoing random allocation of subjects, the local resources for data management and tracking of patients' use of clinical services, and how combining this information system into a randomized primary care system has fostered successful ventures in clinical investigation.

Health Services Research↗
PubMed1990

Predictors of bone mass in perimenopausal women. A prospective study of clinical data using photon absorptiometry.

STUDY OBJECTIVE: To determine whether clinically available data on risk factors are adequate to identify perimenopausal women with either low or high bone mass. DESIGN: Cross-sectional observational study of a cohort of perimenopausal women (mean age, 50.8 years). SETTING: Community volunteers in a university hospital. SUBJECTS: One hundred twenty-four white volunteers established as perimenopausal by history and serum concentrations of estrogens and follicle-stimulating hormone. MEASUREMENTS AND MAIN RESULTS: Models were constructed to predict bone mass in the radius, lumbar spine, and hip using risk factors (age, height, weight, calcium and caffeine intake, alcohol and tobacco use, and urinary markers of bone turnover). Although highly significant predictive models were developed for all skeletal sites, none of the models correctly identified more than 70% of women with low bone mass at any site. However, for the radius, a model was constructed that never overestimated bone mass by more than 0.10 g/cm. A small subgroup (7%) with short stature, low body weight, low calcium intake, and who were heavy smokers always had low radial bone mass. Using these models, about 30% of our population could be assessed without bone mass measurements. Predictions for the spine and femur were less efficient, suggesting that direct measurements are required if therapy decisions are to be based on bone mass at these sites. CONCLUSIONS: Risk factors for osteoporosis are of limited use in identifying women with low bone mass around the time of menopause. Measurements of bone mass are probably necessary if the risk for osteoporosis is to be the basis for deciding on estrogen replacement therapy.

Absorptiometry, Photon↗
PubMed1990

The contribution of bone loss to postmenopausal osteoporosis.

We have addressed the relative importance of peak bone mass and subsequent rate of loss in determining postmenopausal women's bone mass in old age, by examining longitudinal measurements of radial mid-shaft bone mass on various samples of healthy white postmenopausal women. Using both the variance estimate of age-specific rates of bone loss and the population variance in bone mass, we determined that rates of loss could contribute importantly to future bone mass. However, since we found a small negative correlation between initial bone mass and rate of loss, it was necessary to estimate the effect of bone loss as the complement of the contribution of initial bone mass. We found that the influence of bone loss (relative to initial bone mass) increases as the women age, such that by about age 70, the contribution of initial bone mass and rate of loss approached equality. However, estimated rates of bone loss were not very stable over time, so it was difficult to identify long-term 'fast-losers'. We conclude that the rate of postmenopausal bone loss is an important contributor to osteoporosis at old age, but it is difficult to identify long-term fast-losers, thereby reducing the clinical value of assessments of rates of change in bone mass early in the postmenopause.

Aged↗
PubMed1990

Bone mass and anthropometric measurements in adult females.

Bone mass and anthropometrics were measured in 342 adult female twins, aged 25-79 (mean = 44.1 years) for the purpose of: (1) identifying which anthropometric measurements were most strongly associated with bone mass at various skeletal sites, and (2) determining the accuracy of combinations of these measurements in the prediction of bone mass. Among the eight skinfolds measured, the subscapular site was more strongly correlated with all bone mass measurements than any other skinfold. Similarly, calf circumference (among four sites) and biacromial width (among five frame size measurements) provided the strongest correlations within these groups of anthropometrics with all bone sites. The somewhat surprising consistency of these results was then tested in multivariable models for the prediction of bone mass. For the entire study group, each of the anthropometric measurements (subscapular skinfold, calf circumference and biacromial width) were independent, significant predictors of bone mass, even when height, weight and age were included in the models. These data suggest that frame size, muscularity and adiposity have independent effects on the skeleton, and that single measurements of each of these anthropometric characteristics are associated with all skeletal sites.

Adipose Tissue↗
PubMed1990

Ibuprofen-associated renal impairment in a large general internal medicine practice.

The authors determined the incidence of ibuprofen-associated renal impairment and risk factors for its development in 1908 patients treated with ibuprofen using data from a computerized medical records system. Renal impairment occurred in 343 patients (18%). Multivariable analysis revealed six independent predictors of renal impairment: age, prior renal insufficiency, coronary artery disease, male gender, elevated systolic blood pressure, and diuretic use. They then tested the degree to which ibuprofen contributed to the development of renal impairment by evaluating a control group of 3933 acetaminophen recipients. Neither ibuprofen nor acetaminophen was among the independent predictors of risk when all patients were considered (adjusted odds ratio, 1.05; 95% Cl, 0.88-1.26). However, two subsets of at risk patients had an ibuprofen effect: patients greater than or equal to 65 years of age who received ibuprofen were at greater risk of renal impairment as compared to acetaminophen recipients (adjusted odds ratio, 1.34; 95% Cl, 1.05 to 1.72) as were patients with coronary artery disease (adjusted odds ratio, 2.54; 95% Cl, 1.38 to 4.68). Their results suggest that elderly patients and patients with coronary artery disease are at risk for ibuprofen-associated renal impairment and therefore should have their renal function monitored when ibuprofen and possibly other nonsteroidal anti-inflammatory drugs are prescribed.

Acetaminophen↗
PubMed1989

Baseline measurement of bone mass predicts fracture in white women.

STUDY OBJECTIVE: To determine if a single bone mass measurement of the radius is predictive of future fractures at any site. DESIGN: Observational study of a cohort of free-living subjects and a cohort of retirement-home residents with an average follow-up of 6.7 years and 5.5 years, respectively (range, 1 to 15 years for both cohorts). SETTING: General community and a retirement home. SUBJECTS: Volunteer sample of white women (386 free-living and 135 living in a retirement home) who were free of disease and were not receiving medication known to affect bone metabolism. In terms of physical condition subjects ranged from the totally independent to the wheelchair-bound. MEASUREMENTS AND MAIN RESULTS: A radial bone mass measurement was done at the initial visit. Subsequent non-spine fractures were reported by the subjects at follow-up visits, which were less than a year apart in most cases, and verified with medical records. Cox regression was used to model time to first fracture as a function of age and bone mass. These analyses showed that for every 0.1 g/cm decrement in bone mass, the relative risk of fracture was 2.2 (CI, 1.7 to 2.8) for the free-living and 1.5 (CI, 1.2 to 1.9) for the retirement-home residents. Baseline age did not predict the risk of fracture in either cohort, and controlling for baseline age did not reduce the relative-risk estimates of bone mass. Similar analyses also showed that bone mass was a statistically significant predictor for first hip fractures (n = 30) among the nursing-home residents (relative risk, 1.9; CI, 1.4 to 2.7) and first forearm fractures (n = 10) among the free living (relative risk, 3.6; CI, 1.9 to 6.8). For both cohorts, the 8-year probability of any nonspine fracture was about 80% for subjects with initial bone mass less than 0.6 g/cm and was less than 10% for subjects with initial bone mass greater than 0.8 g/cm. Similarly, those in the retirement home with bone mass below 0.6 g/cm had a 6-year probability of hip fracture of 43%, compared with a 17% risk for those with greater bone mass. CONCLUSION: A single bone mass measurement of the radius is predictive of future nonspine fractures at all sites, and at both the forearm and the hip. Baseline age was not a significant predictor of fracture within either cohort. Relative-risk estimates were not dissimilar across fracture sites.

Adult↗
PubMed1989

Cigarette smoking, obesity, and bone mass.

This study was designed to assess the effects of smoking on bone mass and bone loss and to ascertain whether these effects are independent of effects on adiposity and hormone concentrations. A total of 84 healthy, peri- and postmenopausal women were studied prospectively over 3 1/2 years. Heavy smokers had significantly (p less than 0.05) lower radial and vertebral bone mineral content than light or nonsmokers (who did not differ from each other). In regression models, which contained measurements of obesity, pack-years smoking remained a significant predictor of bone mass. However, there were no detectable effects of smoking on rates of bone loss at any site. Smokers appear to be at greater risk of osteoporosis due to their lower bone mass. However, this reduced bone mass is already present around the time of menopause, and rates of bone loss during this period do not appear to be influenced by smoking. Furthermore, we have previously shown in this population that menopausal serum estrogen concentrations (which determine rates of bone loss) do not differ between the smokers and nonsmokers. Further studies of larger groups are required to determine whether small differences in bone loss may exist, since the power to detect such differences was not ideal in this study.

Aging↗
PubMed1989

Variance estimation for medical decision analysis.

We have derived the variance of an expected utility for a probability tree in medical decision analysis based on a Taylor series approximation of the expected utility as a function of the probability and utility values used in the decision tree. The resulting variance estimate is an algebraic expression of the variances associated with the probability and utility estimates used. We also derive expressions for the case where the input parameter estimates are not independent. We discuss the choice of input parameters and their variance estimates and give an example that compares two protocols for the treatment of chlamydial infection.

Analysis of Variance↗
PubMed1989

Liposome-encapsulated 3H-5FU in rabbits.

We compared the pharmacokinetics of liposome-encapsulated tritiated 5-fluorouracil (3H-5FU-Lipo) to 3H-5FU in buffered saline (3H-5FU-PBS) after subconjunctival or intravitreal injection into rabbit eyes. Liposomes were prepared using phosphatidylcholine, phosphatidic acid, and alpha-tocopherol. Following a unilateral subconjunctival injection of either 3H-5FU-Lipo or 3H-5FU-PBS, rabbits were sacrificed at 0.5, 1, 4, and 8 hours. Significantly higher (p less than 0.05) drug levels were achieved with the encapsulated drug in the vitreous at all four time points and in the aqueous at three of four time points. Following bilateral intravitreal injections of 500 micrograms of 5FU in 0.1 ml, as either 3H-5FU-Lipo or 3H-5FU-PBS injected rabbits were sacrificed at 0, 6, 12, 24, and 48 hours. Vitreal drug levels were significantly higher (p less than 0.05) with encapsulated drug at all time points from 6 hours on. At 48 hours, the vitreal level with the encapsulated drug was 578 +/- 0.23 micrograms/ml compared with 1.06 +/- 0.07 micrograms/ml for 3H-5FU-PBS.

Analysis of Variance↗
PubMed1989

Serum from patients with various thrombopoietic disorders alters terminal cytoplasmic maturation of human megakaryocytes in vitro.

Human bone marrow was depleted of progenitors (CFU-MK), but enriched for recognizable megakaryocytes (MK), and placed in cultures with serum from either normal donors (NABS) or patients with primary (PTS) or secondary (STS) thrombocytosis, autoimmune thrombocytopenia (ATS) or aplastic anemia (AAS). Mean MK diameters shifted during the 3-4 days of incubation. Endomitotic figure were visible and mean ploidy increased slightly during cytoplasmic maturation, where decreases in immature cells (stages 1 and 2) were accompanied by increases in the mature MK (stages 3 and 4). Cytoplasmic maturation was faster in AAS, ATS and STS than PTS or NABS; mean size and ploidy were similar in all cultures. Recognizable MK were not forced to undergo additional endoreduplication in response to stimulation. Only AAS augmented MK colony formation, which indicated that at least two humoral factors can regulate megakaryocytopoiesis at separate levels, the progenitors and morphologically recognizable MK.

Anemia, Aplastic↗
PubMed1987

Free estradiol, free testosterone, and sex hormone-binding globulin in perimenopausal women.

To determine whether menstrual status had an effect on plasma sex hormone-binding globulin (SHBG) capacity and nonprotein-bound estradiol (% free E2) and testosterone (% free T), we measured these as well as plasma FSH, total E2, and T and the MCRs of E2 and T in a group of 78 perimenopausal women. The women were allocated to 4 groups: women with cycles whose plasma FSH level was less than 40 mIU/mL (A; n = 16), women with cycles whose plasma FSH level was greater than 40 mIU/mL (B; n = 19), women who were amenorrheic for less than 1 yr (C; n = 13), and women who were amenorrheic for more than 1 yr (D; n = 30). The mean plasma SHBG values were 51.4 +/- 5.7 (+/- SE), 48.3 +/- 4.3, 45.9 +/- 5.4, and 51.1 +/- 3.7 nM in groups 1-4 respectively, and were not significantly different from one another. The mean % free E2 and % free T values also were not different between the groups. However, the mean total E2 and free E2 (% free E2 X E2/100) concentrations were significantly (P less than 0.05) higher in both groups A and B than in groups C and D. The E2 concentration was also higher in group A than in group B. There were strong correlations between the E2 and free E2 concentrations between the T and free T (% free T X T/100); (P less than 0.0001) concentrations, between SHBG capacity and weight, and between the MCRs of both E2 and T and % free E2 and % free T. In normal women, the menopause is not associated with changes in SHBG or % free steroids. Hence, the measurement of E2 could be used to predict the mass of free E2 in these women.

Adult↗
PubMed1977

Lung function, respiratory disease, and smoking in families.

Respiratory symptoms, disease and lung function were studied in 376 families with 816 children who participated in a survey in three USA towns. Parental smoking had no effect on children's symptoms and lung function. Also, there was no evidence that passive smoking affected either lung function or symptoms of adults. There was no association between prevalence of self-reported cough and/or phlegm in parents and their children. There was a highly significant association between the prevalence of wheeze in parents and their younger children, for whom parents reported this symptom. Wheeze in children was also significantly associated with a parental history of asthma, and lung function was lower in children with a family history of asthma. Even after accounting for height, weight, age, sex and race, children's lung function correlated significantly with parents' lung function. However, the contribution of familial factors (i.e., parents' lung function, smoking, and history of asthma) to children's lung function is small compared to the effects of height, weight and age.

Adolescent↗
PubMedDate not supplied

Using clinical data to predict abnormal serum electrolytes and blood cell profiles.

OBJECTIVE: To identify clinical predictors of five abnormalities on the serum electrolyte panel and two abnormalities on the blood cell profile, to study which data elements carried predictive information, and to measure the predictive accuracy and stability of the resulting predictive equations. DESIGN: Prospective data collection from a computerized medical database supplemented by data entered by physicians who ordered outpatient tests into microcomputers. Equations were derived during an eight-month period and later validated twice in the same setting. SETTING: Academic primary care practice affiliated with a county hospital. PATIENTS AND PARTICIPANTS: Patients were mostly black women; physicians were full-time academic general internists and medical residents. MEASUREMENTS AND MAIN RESULTS: There were 6,570 electrolyte and blood cell profile panels ordered during the equation derivation period. The mean receiver operating characteristic (ROC) curve area for the seven equations was 0.849. For the 4,977 tests ordered during ten months of prospective validation, the mean ROC curve area was only 3% less. For three equations, ROC curve areas were lower for patients with unscheduled visits than for those with scheduled visits (p less than 0.05). Except for two equations involving abnormalities with very low prevalences, the equations were also well calibrated. Prior results for the abnormality being considered were the strongest predictors, followed by other laboratory results, diagnoses, and the physicians' estimate of the probability that the test would be abnormal. CONCLUSIONS: Clinical data can accurately predict abnormal results of common outpatient laboratory tests. Computers can help find the necessary data and produce estimates of risk.

Blood Cells↗
PubMedDate not supplied

Effects of computer reminders for influenza vaccination on morbidity during influenza epidemics.

To study the effects of computer-generated reminders for influenza vaccination of patients at high risk of pulmonary disease during the winter, we selected 4555 such patients from a population of 15,000 adults who participated in a three-year randomized trial of preventive-care reminders. The physicians who received the reminders vaccinated eligible patients twice as often as did the control physicians (P = 0.0001). There was a linear increase in the incidence of influenza in our area during the three winters under study (from 1000 to 33,451 to 71,075 cases per year), and we modeled the percentage of patients with hospitalizations, emergency room visits with chest radiography, and blood gas determinations as a logistic function of this increase. The difference in linear trends between the patients in the intervention group (whose physicians received reminders) and those in the control group was significant for emergency room visits (P less than 0.05), hospitalizations (P less than 0.01), and blood gas determinations (P less than 0.001). The most likely explanation for the difference is the greater use of influenza vaccine in the intervention group.

Aged↗