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PubMed2004

Investigation of relationship between change in locoregional control and change in overall survival in randomized controlled trials of modified radiotherapy in head-and-neck cancer.

PURPOSE: To establish whether a relationship exists between improvement in locoregional control (LRC) and improvement in overall survival (OS) in trials of modified radiotherapy for head-and-neck cancer and to attempt to quantify the relationship. METHODS AND MATERIALS: A systematic review of the literature was performed for randomized controlled trials of radiotherapy for head-and-neck cancer involving the use of altered fractionation or hypoxic sensitizers. The changes in LRC at 2 years and OS at 5 years were recorded for each trial. Regression analysis was used to investigate the relationship between the two variables. RESULTS: Nineteen relevant trials were identified. Fourteen reported sufficient data for analysis. Linear regression analysis showed a statistically significant correlation between LRC and OS with a slope of 0.67 (95% confidence interval, 0.38-0.96, p = 0.00017). CONCLUSIONS: We have demonstrated a relationship between a change in LRC and a change in OS in randomized trials of modified radiotherapy for head-and-neck cancer. A 10% improvement in the 2-year LRC is predicted to lead to a 6.7% improvement in the 5-year OS. This type of analysis may have applications in other tumor sites.

Dose Fractionation, Radiation↗

PubMed2003

A regressive model analysis of congenital sensorineural deafness in German Dalmatian dogs.

The objective of the present study was to analyze the mode of inheritance for congenital sensorineural deafness (CSD) in German Dalmatian dogs by consideration of association between phenotypic breed characteristics and CSD. Segregation analysis with regressive logistic models was employed to test for different mechanisms of genetic transmission. Data were obtained from all three Dalmatian kennel clubs associated with the German Association for Dog Breeding and Husbandry (VDH). CSD was tested by veterinary practitioners using standardized protocols for Brainstem Auditory-Evoked Response (BAER). The sample included 1899 Dalmatian dogs from 354 litters in 169 different kennels. BAER testing results were from the years 1986 to 1999. Pedigree information was available for up to seven generations. The segregation analysis showed that a mixed monogenic-polygenic model including eye color as covariate among all other tested models best explained the segregation of affected animals in the pedigrees. The recessive major gene segregated in dogs with blue and brown eye color as well as in dogs with and without pigmented coat patches. Models which took into account the occurrence of patches, percentage of puppies tested per litter, or inbreeding coefficient gave no better adjustment to the most general (saturated) model. A procedure for the simultaneous prediction of breeding values and the estimation of genotype probabilities for CSD is expected to improve breeding programs significantly.

Animals↗

PubMed2001

Unstimulated salivary flow rates of young children.

OBJECTIVE: Studies on salivary flow rates in human beings have mainly been carried out with adults. The purpose of this study was to determine the unstimulated salivary flow rates of children 4 to 7 years old. In addition, the relative contributions of the variables age, gender, race, height, body weight, dentition status, use of prescription medication, and health status (information obtained from parents) to the unstimulated salivary flow rates of children were also studied. STUDY DESIGN: Data were obtained from children (n = 447) at 2 sites in the United States (site 1, southeast Michigan; site 2, northern Michigan) and at 5 sites in Brazil (site 3, Porto Alegre; site 4, São Paulo; site 5, Belém; and sites 6 and 7, sites in Rio de Janeiro). In northern Michigan (site 2) the participants were cognitively or developmentally disabled, or both. In Rio de Janeiro (site 7), a group of 8- to 12-year-olds served as a control group. Saliva samples were collected for 3 minutes between 9 AM and noon in the spring or summer, and the saliva rate was determined gravimetrically. Data were analyzed by analysis of variance, bivariate analysis, and regression analysis. RESULTS: The secretion rates at the 7 sites were (in milliliters per minute) 0.19 +/- 0.15, 0.23 +/- 0.28, 0.34 +/- 0.23, 0.48 +/- 0.37, 0.25 +/- 0.27, 0.37 +/- 0.28, and 0.61 +/- 0.34, respectively. There were significant differences among sites (P <.0001). The older group (site 7) had flow rates that were significantly higher than the flow rates of any other group. In addition, children from Michigan (sites 1 and 2) had significantly lower rates than most groups of children in Brazil. Girls had lower unstimulated salivary flow rates than boys did at all the sites, but the differences were not statistically significant. Race was shown not to affect the flow rates. The use of any prescription medication by children in the previous 3 months was associated with lower salivary flow rates than were found in children not using prescription medication. Children who were in good health and who had no previous medical conditions had higher flow rates--but not significantly so. Higher flow rates occurred in children with mixed dentition than in children with primary dentition, although again the differences were not statistically significant. Regression analysis revealed weight to be of significance in explaining the variability of the unstimulated salivary flow rates at 2 sites, height at 1 site, the use of prescription medication at 2 sites, and age at 1 site. CONCLUSIONS: The unstimulated salivary flow rates in children in the northern United States are comparable with those reported for Japanese children, whereas the flow rates of children in Brazil are comparable with those reported for North American and European adults. In addition, none of the demographic variables/parameters tested contributed consistently to the variability of the unstimulated salivary flow rates in children at the 7 sites assessed in this study.

Age Factors↗

PubMed2001

The reliability of plain radiography in experimental fracture healing.

OBJECTIVE: To investigate the reliability of radiographs in the evaluation of healing of closed fractures. DESIGN: A closed midshaft tibial fracture was created in 40 goats and stabilized with an external fixator. The animals were assigned to four groups: no injection, injection of 1 mg osteogenic protein-1 (OP-1), 1 mg OP-1 with collagenous carrier, or carrier alone. Radiographs were performed weekly until the animals were killed after 2 and 4 weeks. Healing was evaluated using radiographs, biomechanical testing, and histological examination. All radiographs were examined by two independent observers. Interobserver agreement was calculated and radiographic scores were compared with mechanical and histological scores using regression analysis. RESULTS: Regression analysis showed poor correlation between radiographic scores and biomechanical and histological data. Correlation coefficients varied between 0.39 and 0.63. Good agreement between the observers was seen in only three parameters: visibility of the fracture line, weightbearing ability, and a combined healing parameter. CONCLUSION: Plain radiography provides poor parameters for monitoring the fracture healing process.

Animals↗

PubMed2000

Factors influencing arterial oxygenation early after bidirectional cavopulmonary shunt without additional sources of pulmonary blood flow.

OBJECTIVES: Although the arterial oxygen saturation after bidirectional cavopulmonary shunting should theoretically be homogeneous if additional pulmonary flow is obliterated, the arterial oxygen saturation has been found to vary in clinical practice. Knowledge of the preoperative and operative determinants of arterial oxygen saturation early after bidirectional cavopulmonary shunting may lead to a better understanding of this unique physiology. METHODS: Thirty-five patients who underwent bidirectional cavopulmonary shunting with obliteration of additional pulmonary flow were included in this study. The arterial oxygen saturation was determined at the 5 time points over a 48-hour period. Multivariable regression analysis was used to identify the independent predictors of the arterial oxygen saturation. RESULTS: No significant interval changes occurred in the arterial oxygen saturation during the 48 hours after bidirectional cavopulmonary shunting, which ranged from 61.6% to 95.6%. There was a significant inverse correlation between the postoperative superior vena cava pressure and the arterial oxygen saturation (P =.003). A low arterial oxygen saturation early after bidirectional cavopulmonary shunting was a predictor of mortality or exclusion from univentricular repair within 24 months (P =.012, odds ratio = 1.14). Of 11 factors identified by univariable analysis, multiple regression analysis indicated that age less than 8 months at the time of shunting (P <.0001) and ventricular volume overload (P =. 002) predicted a lower arterial oxygen saturation after bidirectional cavopulmonary shunting. CONCLUSIONS: Even without additional sources of pulmonary blood flow, several preoperative factors, including younger age and severe ventricular volume overload, predicted a decrease in the arterial oxygen saturation early after bidirectional cavopulmonary shunting. This, in turn, predicted poor outcome during 2 years of follow-up.

Adolescent↗

PubMed1993

Prediction of in vitro fertilization rates from semen variables.

OBJECTIVE: To assess the value of semen variables for predicting fertilization rates. DESIGN: Measures of the fresh semen and the motile sperm fraction used for insemination were related to the fertilization rate by multiple regression analysis. The regression model was then used to construct a two-dimensional clinical chart. SETTING: University-affiliated reproductive medicine unit. PATIENTS: The results of 294 IVF cycles were analyzed retrospectively. Selection criteria were: [1] first cycle of IVF; [2] tubal and/or male factor infertility; and [3] four or more oocytes inseminated. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The fertilization rate was related to measured variables of the fresh semen and the motile sperm fraction used for insemination. Fertilization rate was categorized as poor (< 35%) or acceptable (> or = 35%). RESULTS: Multiple regression analysis demonstrated a strong correlation between the fertilization rate and the combined indexes of percentage normal morphology and grade of motility in the fresh semen and percentage progressive motility in the motile sperm fraction. A two-dimensional chart that expressed these relationships was constructed. Its accuracy of prediction was 77% for poor fertilization and 95% for acceptable fertilization. CONCLUSIONS: The fertilization rate is strongly correlated with percentage normal sperm morphology in the fresh semen and the percentage progressive motility in the motile sperm fraction used for insemination. The clinical chart provides a simple but powerful tool for predicting fertilization outcome.

Confidence Intervals↗

PubMed2006

Effect of aging and degeneration on disc volume and shape: A quantitative study in asymptomatic volunteers.

Debate continues on the effect of disc degeneration and aging on disc volume and shape. So far, no quantitative in vivo MRI data is available on the factors influencing disc volume and shape. The objective of this MRI study was to quantitatively investigate changes in disc height, volume, and shape as a result of aging and/or degeneration omitting pathologic (i.e., painful) disc alterations. Seventy asymptomatic volunteers (20-78 years) were investigated with sagittal T1- and T2-weighted MR-images encompassing the whole lumbar spine. Disc height was determined by the Dabbs method and the Farfan index. Disc volume was calculated by the Cavalieri method. For the disc shape the "disc convexity index" was calculated by the ratio of central disc height and mean anterior/posterior disc height. Disc height, disc volume, and the disc convexity index measurements were corrected for disc level and the individuals age, weight, height, and sex in a multilevel regression analysis. Multilevel regression analysis showed that disc volume was negatively influenced by disc degeneration (p < 0.001) and positively correlated with body height (p < 0.001) and age (p < 0.01). Mean disc height and the disc convexity index were negatively influenced by disc degeneration but not by gender, weight, and height. Disc height was positively correlated with age (p < 0.01). From the results of this study, it can be concluded that disc degeneration generally results in a decrease of disc height and volume as well as a less convex disc shape. In the absence of disc degeneration, however, age tends to result in an inverse relationship on disc height, volume, and shape.

Adult↗

PubMed1998

Dietary intake of antioxidant (pro)-vitamins, respiratory symptoms and pulmonary function: the MORGEN study.

BACKGROUND: A study was undertaken to investigate the relationships between the intake of the antioxidant (pro)-vitamins C, E and beta-carotene and the presence of respiratory symptoms and lung function. METHODS: Complete data were collected in a cross sectional study in a random sample of the Dutch population on 6555 adults during 1994 and 1995. Antioxidant intake was assessed by a semi-quantitative food frequency questionnaire and respiratory symptoms (cough, phlegm, productive cough, wheeze, shortness of breath) were assessed by a self-administered questionnaire. Prevalence odds ratios for symptoms were calculated using logistic regression analysis. Linear regression analysis was used for forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The results are presented as a comparison between the 90th and 10th percentiles of antioxidant intake. RESULTS: Vitamin C intake was not associated with most symptoms but was inversely related with cough. Subjects with a high intake of vitamin C had a 53 ml (95% CI 23 to 83) higher FEV1 and 79 ml (95% CI 42 to 116) higher FVC than those with a low vitamin C intake. Vitamin E intake showed no association with most symptoms and lung function, but had a positive association with productive cough. The intake of beta-carotene was not associated with most symptoms but had a positive association with wheeze. However, subjects with a high intake of beta-carotene had a 60 ml (95% CI 31 to 89) higher FEV1 and 75 ml (95% CI 40 to 110) higher FVC than those with a low intake of beta-carotene. CONCLUSIONS: The results of this study suggest that a high intake of vitamin C or beta-carotene is protective for FEV1 and FVC compared with a low intake, but not for respiratory symptoms.

Adult↗

PubMed1999

Axial and peripheral bone mineral acquisition: a 3-year longitudinal study in Chinese adolescents.

UNLABELLED: We performed a 3-year longitudinal study of a group of 179 healthy Chinese adolescents (92 boys and 87 girls) aged from 12 to 16 years to determine the effects of puberty, physical activity, physical fitness, and calcium intake on the acquisition of bone mass. At yearly intervals for 3 consecutive years we recorded nutrition, calcium intake and anthropometric measurements, and assessed pubertal status according to Tanner. Bone mass of the lumbar spine was determined by dual-energy X-ray absorptiometry and radial bone mass by single-photon absorptiometry. Physical fitness and level of physical activity were assessed and muscle strength and power determined by isokinetic testing. Peripheral bone mass correlated with axial skeleton bone mass. Age, pubertal staging, physical fitness and muscle strength were significantly associated with bone mass increments on cross-sectional univariate and regression analysis. Longitudinal regression analysis showed that the most important factor affecting bone mass accretion in adolescents in both sexes was their pubertal stage. In boys, bone mass increment throughout the study was greater in children who were already in the advanced pubertal stages on entering the study than in those who started puberty in year 2 or 3 of the study. The percentage change in bone mineral content of the forearm and in bone mineral density of the lumbar spine was greater than 25% in the advanced pubertal group as compared to around 20% in the less mature group. For girls, the reverse was true. The increment of bone mass during the study period was significantly greater in those who presented in the earlier pubertal stages than in those who were at the more advanced stage of puberty on entry into the study. There was no significant effect of calcium intake and physical activities on the bone mass accretion. CONCLUSION: In Chinese adolescents, bone mineral accretion at adolescence is not influenced by exercise, level of physical fitness and calcium intake. In both sexes, and especially in girls, to optimally increase bone mass, regular physical exercise programmes should be instituted well before the onset of puberty rather than at or after it. Once puberty starts, these interventions may have no or only limited effect.

Adolescent↗

PubMed2005

Development and validation of a questionnaire to identify learning-oriented group interactions in PBL.

Collaborative learning attracts attention because of its potential as a powerful learning strategy. This also holds for PBL. However, group work in PBL sometimes encounters problems and the quality of interaction is not always at the desired level. The aim of the present study was to develop and validate a questionnaire to assess the quality of learning-oriented group interactions in PBL in an uncomplicated way. The questionnaire, to be completed by students involved in PBL, contained items on three group-interaction dimensions: exploratory questions, cumulative reasoning and handling conflicts. It was validated by means of confirmatory factor analysis and regression analysis, the latter to investigate the relation between the three-dimension model and the tutorial group's productivity. The factors underlying the questionnaire were confirmed by the data in a linear structural analysis of the data. The regression analysis showed that the 'exploratory questions' and 'cumulative reasoning' factors explained together 26% of the variance of the tutorial group's productivity. This study provided evidence for the validity of the questionnaire. The instrument contains tips for students and tutors to stimulate deep processing interactions in the tutorial group. Nevertheless, it seems useful to investigate the external validity of the questionnaire.

Cooperative Behavior↗

PubMed1991

[Prediction of 24-hour urinary creatinine excretion from age, body weight and height of an individual and its application].

Equations to predict 24-hour urinary creatinine excretion (UcrV) from age, body weight (W) and body height (H) were developed based on the data for UcrV determined by collecting 24-hour urine for 3-5 days in 256 male and 231 female clinically healthy subjects, aged from 20 to 84 years. By regression analysis a regression equation was developed. Multiple regression analysis revealed that age, W and H contributed most to the measured value of UcrV. The regression equations to predict UcrV from age, W and H were as follows: Predicted value of UcrV (PRCr) = -12.63 x Age + 15.12 x W + 7.39 x H - 79.90 (male: mg/day) PRCr = -4.72 x Age + 8.58 x W + 5.09 x H - 74.50 (female: mg/day) The multiple correlation coefficients were 0.87 for males and 0.73 for females, respectively. The difference between PRCr and measured UcrV (residual) was +0.81 +/- 154 (SD) mg/day on the average. An analysis of residuals by means of plotting of standardized residuals and predicted standardized dependent variables showed no remarkable deviations in both sexes, suggesting that these equations are applicable to the prediction of UcrV. These equations were applied to 38 Japanese men and women who were asked to collect 24-hour urine for 14 days on average, and also to 47 foreigners (American, Nepalese and Italian). The average residual in the former was +27 +/- 87 mg/day and that in the latter -3 +/- 85 mg/day, suggesting that these equations can be applied not only to the Japanese but also to the foreigners as a useful index in predicting 24-hour urinary creatinine excretion.

Adult↗

PubMed2000

Renal effects of cadmium exposure in cadmium nonpolluted areas in Japan.

Long-term exposure to cadmium (Cd) causes renal damage in the general population. The maximum allowable urinary Cd concentration, which was calculated from our previous study performed in a Cd-polluted area, was almost the same as the mean urinary Cd concentration of people living in nonpolluted areas. We assessed whether environmental Cd exposure is related to renal dysfunction of people in nonpolluted areas in Japan. Blood and urine samples were collected from 2753 subjects (1105 men and 1648 women) ages over 50 years old in three nonpolluted areas. Blood was analyzed for Cd and urine was analyzed for Cd, total protein, beta(2)-microglobulin (beta(2)-mg), and N-acetyl-beta-D-glucosaminidase (NAG). Cd in blood or urine was employed as indicators of internal dose; and urinary total protein, beta(2)-mg, and NAG were used as an indicator of renal dysfunction. Multiple regression analysis and logistic regression analysis were performed to clarify the dose-effect and dose-response relationship between blood or urinary Cd concentration and indicators of renal dysfunction. Multiple regression analysis demonstrated a significant dose-effect relationship between Cd in blood and urine and indicators of renal dysfunction. Logistic regression analysis also showed that the probability that individual subjects would have abnormal values of the renal variables was significantly related to Cd in blood and urine.

Acetylglucosaminidase↗

PubMed1993

Maintenance of bone mass in patients receiving dialytic therapy.

To determine what factors contribute to and change bone mineral density (BMD) in dialysis patients, serial lumbar spine dual x-ray absorptiometry studies were analyzed by stepwise regression analysis in 67 black dialysis patients. The patients were 50.5 +/- 2.0 years of age (mean +/- SE) and 49% were men; the patients had received dialytic therapy for 3.7 +/- 0.5 years. The mean initial BMD z-score was 0.147 +/- 0.182. By cross-sectional analysis, the BMD increased in the male and premenopausal female patients but decreased in the postmenopausal female patients by 2.5% g/cm2/decade of life, less than that observed in black patients with normal renal function. Univariate analysis and stepwise regression analysis demonstrated radiographic evidence of osteopenia (beta-coefficient = -0.180 +/- 0.050; P = 0.001) and prior parathyroidectomy (beta-coefficient = 0.133 +/- 0.070; P = 0.054) as the only variables significantly correlated to the BMD. The effects of biochemical variables and different treatments on the delta BMD, calculated as the difference between each patient's first and second BMDs divided by the interval in years, were evaluated by stepwise regression analysis in 41 patients. The mean interval between the two BMDs was 18.4 +/- 1.02 months (range, 5 to 34 months) and the delta BMD was 0.025 +/- 0.018 g/cm2/yr, increasing in 65% of the patients. By univariate and stepwise regression analysis, the mean monthly serum total alkaline phosphatase concentration was the only variable that correlated with the delta BMD (beta-coefficient = 0.0001; P = 0.030).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2025

Prognostic and immunological implications of sialylation-associated gene signatures in hepatocellular carcinoma.

OBJECTIVE: The absence of effective biomarkers continues to limit early diagnostic accuracy and prognostic evaluation in patients with hepatocellular carcinoma (HCC). Aberrant sialylation (SI) has been demonstrated to contribute to therapeutic resistance and tumor progression. The aim of this investigation was to identify a sialylation-related gene (SRG) signature, evaluate its prognostic significance, and investigate associated immunological characteristics in HCC. METHODS: Transcriptomic profiles and corresponding clinical data for patients with HCC were obtained from UCSC Xena, the International Cancer Genome Consortium (ICGC), and the Molecular Signatures Database (MsigDB). Differential expression analysis, Cox regression analysis modeling, and least absolute shrinkage and selection operator (LASSO) regression analysis were applied to identify independent prognostic markers and develop predictive models. The tumor immune microenvironment and its relationship with the identified SRGs were assessed by evaluating immune infiltration patterns. A gene co-expression network for the prognostic SRGs was constructed using GeneMANIA to identify potentially targetable signaling pathways. RESULTS: Four SRGs (ST6GALNAC4, B4GALT5, B4GALNT1, and NEU1) were significantly associated with the prognosis of patients with HCC. Prognostic models constructed using these genes demonstrated strong predictive performance. Notable differences were observed in immune cell populations and immune checkpoint expression between the high-risk and low-risk groups. Additionally, the half-maximal inhibitory concentration values for 101 therapeutic compounds varied between these groups. Lipopolysaccharide and sphingolipid metabolism were identified as key biological processes linked to tumor progression and modulation of the immune microenvironment. CONCLUSION: The four identified SRGs were significantly associated with clinical outcomes and immunological features in HCC. These findings provide a foundation for advancing early diagnostic strategies, refining prognostic assessments, and guiding personalized therapeutic approaches for patients with HCC.

Humans↗

PubMed2005

Predictors of self-rated health status among Texas residents.

INTRODUCTION: The purpose of this study was to investigate the predictors of self-rated health status for Texas adults using the current 2003 Behavioral Risk Factor Surveillance System data. Self-rated health is generally accepted as a valid measure of health status in population studies, and understanding its correlates may help public health professionals prioritize health-promotion and disease-prevention interventions. METHODS: The two research questions addressed by this study involved the predictors of self-rated health: 1) "Do demographic characteristics, health care coverage, leisure-time physical activity, and body mass index predict self-rated health status for Texas residents aged 18 to 64 years?" and 2) "Does choice of interview language (English vs Spanish) predict self-rated health status for Texas residents of Hispanic ethnicity aged 18 to 64 years?" Key analysis variables were identified, and descriptive statistics were used to describe the major variables and determine whether the number of respondents for each variable was sufficient for analysis. Multivariate regression analysis was used to assess the variables. RESULTS: Multiple logistic regression analysis (controlling for diabetes and arthritis) of the self-rated health predictors indicated that older age, lack of health care coverage, lack of a college education, being Hispanic, having a lower income, obesity, and not exercising explained 19.4% of the variance of fair and poor self-rated health. The interview language (English or Spanish), age, sex, education, income, obesity, health insurance coverage, and physical activity (controlling for chronic illness) explained 22.8% of the variance in fair and poor self-rated health for Hispanic respondents. CONCLUSION: The results of this study suggest that a college education, a lower body mass index, non-Hispanic ethnicity, and participation in physical activity are associated with good, very good, or excellent self-rated health status. The finding that the interview language significantly predicted fair and poor self-rated health substantiates previous research and emphasizes the importance of culturally sensitive approaches to health care services.

Adolescent↗

PubMed1995

Estrogen receptors in 699 primary breast cancers: a comparison of immunohistochemical and biochemical methods.

BACKGROUND: Over the last few years, estrogen receptor (ER) determination by immunohistochemistry (ER-ICA) has been extensively used, but it still remains to be established whether this method can replace the standard biochemical technique using dextran-coated charcoal (ERDCC). PATIENTS AND METHODS: ER were determined by both the dextran-coated charcoal (DCC) method and immunohistochemistry (ICA) in 699 patients with primary breast cancer; other parameters (age, pathological T-pT- and nodal status -pN-, progesterone receptors by DCC, proliferative index by ICA) were also recorded. The 'best' cut-off for ERICA was evaluated by means of Receiver Operating Characteristics (R.O.C.) analysis; logistic regression analysis was used to find adequate 'weights' for stain intensity. RESULTS AND CONCLUSIONS: A significant correlation was found between the two methods (p < 0.001). R.O.C. analysis revealed that the 'best' cut-off for the ERICA score was 45% (sensitivity 0.810, specificity 0.804). Logistic regression analysis showed that an ERICA score which also considers staining intensity does not add any useful information concerning ER content in breast cancers.

Breast Neoplasms↗

PubMed2003

[Time-series analysis on the relationship between air pollution and daily mortality in Beijing].

To quantitively evaluate the associations between ambient air pollutant and daily mortality of Beijing and to supply the scientific bases for formulating control measures. Air pollutants including CO, SO2, NOx, TSP, PM10. time series analysis Poisson regression was used to evaluate the relationship between cause-specific deaths and air pollutant, considering the potential confounding factors such as seasonal and long-term patterns, meteorological factors (air temperature, air humidity), as well as adjusting the influence of flu epidemics in winter of 1998. The results showed that in single-factor Poisson regression analysis, there is a significant positive correlation between the four pollutants and daily mortality except for the relationship between TSP and coronary heart disease deaths. In multi-factor Poisson regression analysis, when SO2 increase in 100 micrograms/m3, respiratory deaths, cardiovascular and cerebro-vascular deaths, coronary heart disease deaths and chronic obstructive pulmonary deaths increased by 4.21%, 3.97%, 10.68%, 19.22% respectively. Meanwhile, each 100 micrograms/m3 increase in TSP associated with 3.19% increase in the respiratory deaths and 0.62% increase in the cardiovascular and cerebrovascular deaths. It is suggested that air pollution is a risk factor for health and an increase of air pollution level might lead to a raise in daily mortality.

Air Pollutants↗

PubMed1997

Mathematical tools for demonstrating the clinical usefulness of biochemical markers.

Various approaches have been proposed for evaluating the diagnostic value of biochemical markers. Careful design of experimental protocol is key in carrying out any evaluation of clinical diagnostic value. A prospective cohort study is the best clinical trial design and should include an appropriate reference (gold) standard applied in every patient, the results of which are assessed blindly. The spectrum of patients evaluated should reflect the population in which the test will be used, be appropriately broad to avoid bias, and include both symptomatic and asymptomatic patients. The handling of indeterminate results and the eligibility criteria for inclusion in the study should be carefully defined. Although sensitivity, specificity, and predictive value have long been used as indices of test accuracy, newer methods such as receiver operating characteristic curve (ROC) analysis, logistic regression analysis and likelihood ratios are more robust indicators that overcome many limitations of the traditional indices. The area under the ROC curve (AUC) is the best global indicator of test accuracy, but comparisons of AUC for different tests must take correlation between the tests into account if they have been performed in the same patients. Logistic regression analysis allows the diagnostic information from several tests to be evaluated multivariately, provides a probability estimate for a given outcome, and requires few assumptions regarding the underlying distributions of test data. Logistic regression also provides a straightforward method for calculating likelihood ratios. Likelihood ratios are useful for interpreting test results in the individual patient because they provide a convenient means to directly determine predictive value without having to calculate sensitivity and specificity for a given decision limit. Application of these methods is demonstrated using specific examples.

Biomarkers↗