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Lawrence Joseph

Publications and source records attributed to Lawrence Joseph.

At least 19 recordsLinked to original sources
PubMed2006

A cross-sectional study of the prevalence of intensity of infection with Schistosoma japonicum in 50 irrigated and rain-fed villages in Samar Province, the Philippines.

BACKGROUND: Few studies have described heterogeneity in Schistosoma japonicum infection intensity, and none were done in Philippines. The purpose of this report is to describe the village-to-village variation in the prevalence of two levels of infection intensity across 50 villages of Samar Province, the Philippines. METHODS: This cross-sectional study was conducted in 25 rain-fed and 25 irrigated villages endemic for S. japonicum between August 2003 and November 2004. Villages were selected based on irrigation and farming criteria. A maximum of 35 eligible households were selected per village. Each participant was asked to provide stool samples on three consecutive days. All those who provided at least one stool sample were included in the analysis. A Bayesian three category outcome hierarchical cumulative logit regression model with adjustment for age, sex, occupation and measurement error of the Kato-Katz technique was used for analysis. RESULTS: A total of 1427 households and 6917 individuals agreed to participate in the study. A total of 5624 (81.3%) participants provided at least one stool sample. The prevalences of those lightly and at least moderately infected varied from 0% (95% Bayesian credible interval (BCI): 0%-3.1%) to 45.2% (95% BCI: 36.5%-53.9%) and 0% to 23.0% (95% BCI: 16.4%-31.2%) from village-to-village, respectively. Using the 0-7 year old group as a reference category, the highest odds ratio (OR) among males and females were that of being aged 17-40-year old (OR = 8.76; 95% BCI: 6.03-12.47) and 11-16-year old (OR = 8.59; 95% BCI: 4.74-14.28), respectively. People who did not work on a rice farm had a lower prevalence of infection than those working full time on a rice farm. The OR for irrigated villages compared to rain-fed villages was 1.41 (95% BCI: 0.50-3.21). DISCUSSION: We found very important village-to-village variation in prevalence of infection intensity. This variation is probably due to village-level variables other than that explained by a crude classification of villages into the irrigated and non-irrigated categories. We are planning to capture this spatial heterogeneity by updating our initial transmission dynamics model with the data reported here combined with 1-year post-treatment follow-up of study participants.

Adolescent↗
PubMed2006

The natural progression of health-related quality of life: results of a five-year prospective study of SF-36 scores in a normative population.

BACKGROUND: Limited information exists regarding the natural progression of health-related quality of life (HRQOL) in the general population, as most research has been cross-sectional or has followed populations with specific medical conditions. Such norms are important to establish, because the effect of any intervention may be confounded by changes due to the natural progression of HRQOL over time. METHODS: Participants were randomly selected from 9 Canadian cities and surrounding rural areas. Changes in the eight domains and 2 summary component scores of the Medical Outcomes Study 36-item short form (SF-36) were examined over a 5 year period (1996/1997-2001/2002). Mean changes were calculated for men and women within 10 year age categories. Multiple imputation was used to adjust for potential selection bias due to missing data. RESULTS: The baseline sample included 6539 women and 2884 men. Loss to follow-up was 17% for women and 23% for men. Mean changes tended to be small, but there was an overall trend towards decreasing HRQOL over time. Changes were more pronounced in the older age groups and in the physically oriented domains. Younger age groups tended towards small mean improvements, particularly in the mentally oriented domains. Large standard errors suggest that on an individual level, large improvements in some participants are balanced by large declines in others. CONCLUSION: In general, the HRQOL of Canadians appears relatively stable over a 5 year period. However, care should be taken when assessing HRQOL longitudinally in certain age or gender groups, as changes associated with an intervention can potentially be confounded by the natural progression of HRQOL.

Adult↗
PubMed2005

Use of complementary and alternative therapies by patients with self-reported chronic back pain: a nationwide survey in Canada.

OBJECTIVE: Complementary and alternative medicine (CAM) is gaining popularity among patients with chronic back pain. We looked for factors associated with CAM use. METHODS: The data came from the cross-sectional household component of the 1996-1997 National Population Health Survey on the health status and behaviors of Canadians. The sample comprising 66.999 individuals aged 20 years or older represented 21 million adults. Cross tabulations were used to estimate the percentage of CAM use among adults with chronic back pain. Factors independently associated with CAM use during the year before the surveys were identified using multiple logistic regression. RESULTS: CAM use was highest in the subgroup of Canadian adults reporting chronic back pain (39.07%). CAM use was associated with younger age, being married, having a higher level of education, and earning a higher income. Overall, the CAM users reported less pain, greater analgesic use, more depression, and more co-morbidities. In addition to CAM, these patients used conventional medical services. CONCLUSION: Our results show that patients with chronic back pain who use CAM are more active, more involved in social life, and healthier, suggesting better management of their condition. They use CAM in addition to, rather than instead of, conventional care. CAM use in these patients may be ascribable to dissatisfaction with mainstream physicians.

Adult↗
PubMed2005

Bayesian modelling of imperfect ascertainment methods in cancer studies.

Tumour registry linkage, chart review and patient self-report are all commonly used ascertainment methods in cancer epidemiology. These methods are used for estimating the incidence or prevalence of different cancer types in a population, and for investigating the effects of possible risk factors for cancer. Tumour registry linkage is often treated as a gold standard, but in fact none of these methods is error free, and failure to adjust for imperfect ascertainment can lead to biased estimates. This is true both if the goal of the study is to estimate the properties of each ascertainment type, or if it is to estimate cancer incidence or prevalence from one or more of these methods. Although rarely applied in the literature to date, when cancer is ascertained by three or more methods, standard latent class models can be used to estimate cancer incidence or prevalence while adjusting for the estimated imperfect sensitivities and specificities of each ascertainment method. These models, however, do not account for variations in these properties across different cancer sites. To address this problem, we extend latent class methodology to include a hierarchical component, which accommodates different ascertainment properties across cancer sites. We apply our model to a data set of 169 lupus patients with three ascertainment methods and eight cancer types. This allows us to estimate the properties of each ascertainment method without assuming any to be a gold standard, and to calculate a standardized incidence ratio for cancer for lupus patients compared to the general population. As our data set is small, we also illustrate the effects as more data become available. We show that our model produces parameter estimates that are substantially different from the currently most popular method of ascertainment, which uses tumour registry data alone.

Bayes Theorem↗
PubMed2005

Fluctuating inflammatory markers in patients with stable ischemic heart disease.

BACKGROUND: C-reactive protein (CRP), a marker of inflammation, is increasingly measured to stratify coronary artery disease risk and guide clinical management. However, little is known about how inflammatory markers fluctuate over time in patients with stable ischemic heart disease. METHODS: We examined serial serum CRP values in 159 patients with histories spanning the clinical spectrum of ischemic heart disease. Two to 8 CRP measurements were made at intervals varying from 15 days to 6 years. Successive interleukin (IL)-6 values were examined in 1 subgroup. Blood samples were always taken when patients were clinically stable, in the absence of any potentially confounding inflammatory condition. RESULTS: C-reactive protein values in individual patients fluctuated considerably when examined in the following ranges: less than 1 mg/L, 1 to 3 mg/L, and greater than 3 mg/L, proposed to indicate low, average, and high risk. Sixty-four patients (40.3%) changed risk category between the first and the second measurement. Within-patient variances of CRP and IL-6 levels were 1.79 mg/L (95% confidence interval, 1.60-2.00) and 2.69 pg/mL (95% confidence interval, 2.29-3.18), respectively. The variability of CRP was consistent over different times and across clinical groups, and independent of body mass index, smoking status, medication, and clinical events. CONCLUSIONS: Relatively important fluctuations in CRP levels in patients with stable ischemic heart disease may be problematic for risk stratification and treatment monitoring. A similar IL-6 variability suggests that these patients have a dynamic inflammatory status whose kinetics may modulate acute coronary risk.

Aged↗
PubMed2005

Impact of a general practitioner educational intervention on osteoarthritis treatment in an elderly population.

PURPOSE: We examined whether a continuing medical education intervention increased general practitioners' ability to select the proper pharmacological treatment for patients with osteoarthritis. SUBJECTS AND METHODS: Eight towns in Quebec, Canada were randomly allocated to one of four intervention options, workshop and decision tree, workshop, decision tree, or no intervention. All general practitioners practicing in each town were eligible to participate. We evaluated all dispensed prescriptions for either a cyclooxygenase (COX)-2 inhibitor, nonselective nonsteroidal anti-inflammatory drug or acetaminophen written by eligible general practitioners between May 2000 and June 2001 to elderly patients suffering from osteoarthritis. We used a multi-level Bayesian hierarchical model to assess the impact of the interventions on prescription adequacy. RESULTS: We analyzed 5318 dispensed prescriptions written by 249 general practitioners in the five-month preintervention period and 4610 dispensed prescriptions written by the same physicians in the five-month postintervention period. A score of zero or one was given to every prescription, with one indicating prescription adequacy according to guidelines provided during the interventions. Bayesian hierarchical models showed some improvement in scores in the post- versus preintervention periods in all four groups. The probability of an improvement in the towns allocated the workshop and decision tree over the control was 94%, compared with 74% in the workshop group and 55% in the decision tree group. CONCLUSION: An interactive approach offered by peers and complemented by easy to use guidelines may enhance the general practitioner's ability to manage osteoarthritis patients.

Acetaminophen↗
PubMed2005

Sensitivities and specificities of spoligotyping and mycobacterial interspersed repetitive unit-variable-number tandem repeat typing methods for studying molecular epidemiology of tuberculosis.

The development of PCR-based genotyping modalities (spoligotyping and mycobacterial interspersed repetitive unit-variable-number tandem repeat [MIRU-VNTR] typing) offers promise for real-time molecular epidemiological studies of tuberculosis (TB). However, the utility of these methods depends on their capacity to appropriately classify isolates. To determine the operating parameters of spoligotyping and MIRU-VNTR typing, we have compared results generated by these newer tests to the standard typing method, IS6110 restriction fragment length polymorphism, in analyses restricted to high-copy-number IS6110 isolates. Sensitivities of the newer tests were estimated as the percentages of isolates with identical IS6110 fingerprints that had identical spoligotypes and MIRU-VNTR types. The specificities of these tests were estimated as the percentages of isolates with unique IS6110 fingerprints that had unique spoligotypes and MIRU-VNTR types. The sensitivity of MIRU-VNTR typing was 52% (95% confidence interval [CI], 31 to 72%), and the sensitivity of spoligotyping was 83% (95% CI, 63 to 95%). The specificity of MIRU-VNTR typing was 56% (95% CI, 51 to 62%), and the specificity of spoligotyping was 40% (95% CI, 35 to 46%). The proportion of isolates estimated to be due to recent transmission was 4% by identical IS6110 patterns, 19% by near-identical IS6110 patterns, 33% by MIRU-VNTR typing, and 53% by spoligotyping. The low calculated specificities of spoligotyping and MIRU-VNTR typing led to misclassification of cases, inflated estimates of TB transmission, and low positive predictive values, suggesting that these techniques have unsuitable operating parameters for population-based molecular epidemiology studies.

Bacterial Typing Techniques↗
PubMed2005

Estimating the intensity of infection with Schistosoma japonicum in villagers of leyte, Philippines. Part I: a Bayesian cumulative logit model. The schistosomiasis transmission and ecology project (STEP).

Intensity profiles for helminths are used to describe population infection status, monitor effectiveness of control programs, and provide accurate data to validate transmission models. This study aims to accurately predict age/gender specific intensity profiles of endemic schistosomiasis japonica infection in the Philippines. Poor sensitivity of the Kato-Katz test and large heterogeneity in infection levels across villages complicate these predictions. Data from 1,989 individuals living in three endemic villages were analyzed with a Bayesian cumulative-logit model adjusting for nonproportional odds, variation between villages, and measurement error. The posterior uncertainty regarding the proportion of individuals in each egg category was high compared with that estimated using a model ignoring measurement error and villages' heterogeneity. The intensity profiles were very different in children less than 7 years old compared with older children and adults. This model could easily be adapted to other parasitic infections or outcomes where an analysis by category would be recommended.

Animals↗
PubMed2004

Risk factors associated with incident clinical vertebral and nonvertebral fractures in postmenopausal women: the Canadian Multicentre Osteoporosis Study (CaMos).

Utilizing data from the Canadian Multicentre Osteoporosis Study (CaMos), we examined the association between potential risk factors and incident vertebral and nonvertebral fractures. A total of 5,143 postmenopausal women were enrolled. Information collected during the study included data from the CaMos baseline and annually mailed fracture questionnaires, the Short Form 36 (SF-36), the Health Utilities Index, and physical measurements. Participants were followed for 3 years. Postmenopausal women were classified into four groups according to their incident fracture status since baseline: those without a new fracture; those with a new clinically recognized vertebral fracture; those with an incident nonvertebral fracture at the wrist, hip, humerus, pelvis, or ribs (main nonvertebral fracture group); and those with any new nonvertebral fracture (any-nonvertebral-fracture group). We performed multivariate Cox proportional hazard analysis using all possible risk factors to determine the association between risk factors and the time to the first minimal trauma fracture. Best predictive models were also determined using variables that were included in the full models. The Bayesian information criterion was used for model selection. For all analyses, relative risks and associated 95% confidence intervals were calculated. During the follow-up period, 34, 163, and 280 women developed a vertebral, a main nonvertebral, or any nonvertebral fracture, respectively. The best predictive models indicated that a five point lower quality of life as measured by the SF-36 physical component summary score was associated with relative risks of 1.21 (95% CI, 1.02 to 1.44), 1.17 (95% CI, 1.07 to 1.28), and 1.19 (95% CI, 1.11 to 1.27) for incident vertebral, main nonvertebral, and all nonvertebral fractures, respectively. In addition, for a one standard deviation (SD=0.12) lower femoral neck BMD, the relative risks for incident vertebral, main nonvertebral, and any nonvertebral fractures increased by 2.73 (95% CI, 1.74 to 4.28), 1.39 (95% CI, 1.06 to 1.82), and 1.34 (95% CI, 1.09 to 1.65), respectively. Furthermore, various anthropometric measures, disease conditions, and medications are associated with a new fracture. Identifying postmenopausal women at risk is important given that fracture prevention therapies are now available.

Adult↗
PubMed2004

Diversity of Mycobacterium tuberculosis isolates in an immigrant population: evidence against a founder effect.

Population-based studies have used DNA typing of Mycobacterium tuberculosis organisms to estimate the extent of ongoing tuberculosis transmission in various communities and to characterize associated risk factors. The finding of matched DNA "fingerprints" among isolates from an immigrant subgroup may reflect transmission in the adopted country but could also reflect limited diversity among M. tuberculosis organisms within that immigrant community. The authors sought to determine which hypothesis is more likely to explain the high frequency of matched isolates among Haitian-born tuberculosis patients in Montreal, Quebec, Canada. The authors determined the number of different bacterial genotypes in this community as compared with other foreign-born tuberculosis patients and applied a recently described measure of genetic similarity between M. tuberculosis organisms ("genetic distance"). Among 76 Haitian-born tuberculosis patients diagnosed during 1996-1998, the authors identified 47 distinct genotypes on the basis of standard IS6110 DNA typing and categorical analysis. In genetic distance analysis, these 47 genotypes showed as great a genetic diversity as that observed among the 191 distinct genotypes identified in 216 other foreign-born tuberculosis patients. A mycobacterial "founder effect" is unlikely to account for the high proportion of shared isolates among Haitian-born Montrealers. Recent transmission remains the most likely explanation.

Adolescent↗
PubMed2004

Selection bias found in interpreting analyses with missing data for the prehospital index for trauma.

OBJECTIVE: To evaluate the effects of missing data on analyses of data from trauma databases, and to verify whether commonly used techniques for handling missing data work well in theses settings. STUDY DESIGN AND SETTING: Measures of trauma severity such as the Pre-Hospital Index (PHI) are used for triage and the evaluation of trauma care. As conditions of trauma patients can rapidly change over time, estimating the change in PHI from the arrival at the emergency room to hospital admission is important. We used both simulated and real data to investigate the estimation of PHI data when some data are missing. Techniques compared include complete case analysis, single imputation, and multiple imputation. RESULTS: It is well known that complete case analyses and single imputation methods often lead to highly misleading results that can be corrected by multiple imputation, an increasingly popular method for missing data situations. In practice, unverifiable assumptions may not hold, meaning that it may not be possible to draw definitive conclusions from any of the methods. CONCLUSION: Great care is required whenever missing data arises. This is especially true in trauma databases, which often have much missing data and where the data may not missing at random.

Database Management Systems↗
PubMed2004

Bayesian statistics for parasitologists.

Bayesian statistical methods are increasingly being used in the analysis of parasitological data. Here, the basis of differences between the Bayesian method and the classical or frequentist approach to statistical inference is explained. This is illustrated with practical implications of Bayesian analyses using prevalence estimation of strongyloidiasis and onchocerciasis as two relevant examples. The strongyloidiasis example addresses the problem of parasitological diagnosis in the absence of a gold standard, whereas the onchocerciasis case focuses on the identification of villages warranting priority mass ivermectin treatment. The advantages and challenges faced by users of the Bayesian approach are also discussed and the readers pointed to further directions for a more in-depth exploration of the issues raised. We advocate collaboration between parasitologists and Bayesian statisticians as a fruitful and rewarding venture for advancing applied research in parasite epidemiology and the control of parasitic infections.

Animals↗
PubMed2004

Health-related quality of life in cardiac patients with dyslipidemia and hypertension.

BACKGROUND: Hypertension is associated with lower health-related quality of life (HRQOL). Similar association may be found for dyslipidemia. However, controversies exist regarding the HRQOL with dyslipidemia. We evaluated the HRQOL of cardiac patients with and without dyslipidemia and hypertension. METHODS: In a cross-sectional study, 284 cardiac patients rated their HRQOL using SF-36 Health Survey (SF-36), and three preference-based measures (Rating Scale, Time Trade-off and Standard Gamble). RESULTS: Compared to those without dyslipidemia, those with dyslipidemia reported better HRQOL on all preference-based measures and most SF-36 scales particularly on the physical health scales. Adjusted mean differences and 95% confidence interval (95% CI) were equal to 4.5 (0.5, 8.5), 10.8 (2.8, 18.8), and 2.2 (0.2, 4.2) on the Physical Functioning, the Role-Physical and the Physical Component Summary scales, respectively. Exactly the opposite trends were observed among patients with hypertension. The adjusted mean differences (95% CI) were equal to -2.7 (-6.7, 1.4), -10.9 (-19.1, -2.8), and -2.9 (-4.9, -0.9) on the Physical Functioning, the Role-Physical and the Physical Component Summary scales, respectively. CONCLUSION: Cardiac patients with hypertension reported lower physical health than those without hypertension while cardiac patients with dyslipidemia reported better physical health than those without dyslipidemia. The reason for these different trends is not known. Possible explanations are discussed.

Adult↗
PubMed2004

Bayesian sample size determination for prevalence and diagnostic test studies in the absence of a gold standard test.

Planning studies involving diagnostic tests is complicated by the fact that virtually no test provides perfectly accurate results. The misclassification induced by imperfect sensitivities and specificities of diagnostic tests must be taken into account, whether the primary goal of the study is to estimate the prevalence of a disease in a population or to investigate the properties of a new diagnostic test. Previous work on sample size requirements for estimating the prevalence of disease in the case of a single imperfect test showed very large discrepancies in size when compared to methods that assume a perfect test. In this article we extend these methods to include two conditionally independent imperfect tests, and apply several different criteria for Bayesian sample size determination to the design of such studies. We consider both disease prevalence studies and studies designed to estimate the sensitivity and specificity of diagnostic tests. As the problem is typically nonidentifiable, we investigate the limits on the accuracy of parameter estimation as the sample size approaches infinity. Through two examples from infectious diseases, we illustrate the changes in sample sizes that arise when two tests are applied to individuals in a study rather than a single test. Although smaller sample sizes are often found in the two-test situation, they can still be prohibitively large unless accurate information is available about the sensitivities and specificities of the tests being used.

Bayes Theorem↗
PubMed2004

Antiphospholipid antibodies and thrombosis: association with acquired activated protein C resistance in venous thrombosis and with hyperhomocysteinemia in arterial thrombosis.

Although antiphospholipid antibodies (aPL) are associated with thrombosis, it is not known who with aPL is at higher risk for thrombosis. It was the aim of this cross-sectional study to investigate how thrombophilic factors contribute to venous or arterial thrombosis in aPL-positive individuals. In outpatient test centres at two tertiary care hospitals, two hundred and eight (208) persons requiring aPL testing were matched by age, gender and centre to 208 persons requiring a complete blood count. Persons were classified as aPL-positive (having anticardiolipin, lupus anticoagulant and/or anti-beta(2)-glycoprotein I antibodies) or aPL-negative. Several thrombophilic factors were studied using logistic regression modelling. Results showed that the aPL-positive group had three-fold more events (37%) than the aPL-negative group (12%). In unadjusted analyses, clinically important associations were observed between factor V Leiden and venous thrombosis, hyperhomocysteinemia and arterial thrombosis, and activated protein C resistance (APCR) and venous thrombosis (OR, 95% CI = 4.00, 1.35-11.91; 4.79, 2.03-11.33; and 2.03, 1.03-3.97, respectively). After adjusting for recruitment group, persons with both APCR and aPL had a three-fold greater risk (OR, 95% CI = 3.31, 1.30-8.41) for venous thrombosis than those with neither APCR nor aPL. Similarly, after adjusting for hypertension, family history of cardiovascular disease, gender and recruitment group, persons with both hyperhomocysteinemia and aPL had a five-fold increased risk (OR, 95% CI = 4.90, 1.37-17.37) for arterial thrombosis compared to those with neither risk factor. In conclusion, APCR phenotype and hyperhomocysteinemia are associated with a higher risk of venous and arterial thrombosis, respectively, in the presence of aPL.

Activated Protein C Resistance↗
PubMed2004

Risk factors for hospitalization and infection in Canadian Inuit infants over the first year of life--a pilot study.

OBJECTIVES: Inuit infants experience higher mortality and poorer health than other Canadian infants, and suffer disproportionately from bacterial and viral infections. A wide range of inter-related factors affect their health and susceptibility to infection. The objective of the study was to describe hospitalization and morbidity patterns in a cohort of 46 healthy Inuit infants from Iqaluit, Nunavut, over their first year of life. STUDY DESIGN: Risk factors for hospitalization and infections were assessed using multiple linear regression. RESULTS: Infants experienced an average of four respiratory tract infections (RTIs) annually, which accounted for half of the hospitalizations in the cohort. Some interesting trends were evident from the assessment of risk factors using multiple linear regression. Adoption was associated with adverse health effects in addition to those that would be expected due to lack of breast-freeding alone; among infants who were not breast-fed, adopted infants had three more RTIs per year than non-adopted infants. CONCLUSION: The results of this pilot study provide support for undertaking larger epidemiological studies in order to clarify the role of these risk factors, so that future preventive efforts can be informed and effective.

Adoption↗