Jacek A Kopec

University of British Columbia - Vancouver, Vancouver, British Columbia, Canada

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Publications (133)434.93 Total impact

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    ABSTRACT: To evaluate the validity (accuracy) and reliability of 2 commonly used clinical methods, 1 indirect (lifts) and 1 direct (tape measure), for assessment of leg length discrepancy (LLD) in comparison to radiograph.
    The Journal of rheumatology. 07/2014;
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    ABSTRACT: To calculate the incidence rates of osteoarthritis (OA) and to describe the changes in incidence using 18 years of administrative health records. We analyzed visits to health professionals and hospital admission records in a random sample (n = 640,000) from British Columbia, Canada, from 1991/1992 through 2008/2009. OA was defined in 2 ways: (1) at least 1 physician diagnosis or 1 hospital admission; and (2) at least 2 physician diagnoses in 2 years or 1 hospital admission. Crude and age-standardized rates were calculated, and the annual relative changes were estimated from the Poisson regression models. In 2008/2009, the overall crude incidence rate (95% CI) of OA using definition 1 was 14.6 (14.0-14.8); [12.5 (12.0-13.0) among men and 16.3 (15.8-16.8) among women] per 1000 person-years. The rates were lower by about 44% under definition 2. For the period 2000/2001-2008/2009, crude incidence rates based on definition 1 varied from 11.8 to 14.2 per 1000 person-years for men, and from 15.7 to 18.5 for women. Annually, on average, crude rates rose by about 2.5-3.3% for both men and women. The age-adjusted rates increased by 0.6-0.8% among men and showed no trend among women. Our study generated updated incidence rates of administrative OA for the Province of British Columbia. Physician-diagnosed overall incidence rates of OA varied with the case definitions used; however, trends were similar in both case definitions. Age-adjusted rates among men increased slightly during the period 2000/2001-2008/2009. These findings have implications for projecting future prevalence and costs of OA.
    The Journal of Rheumatology 04/2014; · 3.26 Impact Factor
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    ABSTRACT: Purpose To assess the association between subchondral sclerosis detected at baseline with MRI and cartilage loss over time in the same region of the knee in a cohort of subjects with knee pain. Methods 163 subjects with knee pain participated in a longitudinal study to assess knee osteoarthritis progression. Subjects received baseline knee radiographs as well as baseline and 3-year follow-up MRI examinations. Baseline subchondral sclerosis and bone marrow lesions (BMLs) were scored semiquantitatively on MRI in each region from 0 to 3. Cartilage morphology at baseline and follow-up was scored semiquantitatively from 0 to 4. The association between baseline subchondral sclerosis and cartilage loss in the same region of the knee was evaluated using logistic regression, adjusting the results for age, gender, body mass index, and the presence of concomitant BMLs. Results The prevalence of subchondral sclerosis detected by MRI in the regions of the knee varied between 1.6% (trochlea) and 17% (medial tibia). The occurrence of cartilage loss over time in regions varied between 6% (lateral tibia) and 13.1% (medial femur). The prevalence of radiographically-detected subchondral sclerosis in compartments varied from 2.9% (patellofemoral) to 14.2% (medial tibiofemoral). In logistic regression models, there were no significant associations between baseline subchondral sclerosis detected by MRI and cartilage loss in the same region of the knee. Conclusion Baseline subchondral sclerosis as detected by MRI did not increase the risk of cartilage loss over time.
    Osteoarthritis and Cartilage 01/2014; · 4.26 Impact Factor
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    ABSTRACT: Abstract Background: Recent research has identified younger women as an "at-risk" population with rising prevalence of cardiac risk factors and excess mortality risk following acute myocardial infarction (AMI). However, population-based data on trends in AMI hospitalization and early mortality post AMI among younger adults is scarce. We, therefore, aimed to provide a 10-year, descriptive analysis of these trends in a Canadian setting. Methods and Results: We assessed trends and sex differences in AMI hospitalization and 30-day mortality rates using negative binomial and logistic regression, respectively. From 2000 to 2009, there were 70,628 AMI hospitalizations in adults aged ≥20 years, in British Columbia, Canada, with 17.1% of cohort being younger adults ≤55 years. Overall, age-standardized AMI rates (per 100,000 population) declined similarly in men (295.8 to 247.7) and women (152.1 to 128.8) [sex-year interaction p=0.81]. However, these trends differed according to age (age-sex-year interaction p=0.02) with increased rates observed only in younger women (+1.7% per year; p=0.04). The 30-day mortality rates declined similarly for women (19.4% to 13.9%) and men (13.0% to 9.3%) (sex-year interaction p=0.33). Yet, younger women continued to have excess mortality risk, compared with younger men, even in the most recent period [odds ratio: 2008-09=1.61 (95% onfidence interval: 1.25, 2.08)]. Conclusion: While the overall AMI hospitalization and 30-day mortality rates significantly declined in women and men, hospitalization rates in women ≤55 years increased and their excess risk of 30-day mortality persisted. These findings highlight the need to intensify strategies to reduce the incidence of AMI and improve outcomes after AMI in younger women.
    Journal of Women s Health 11/2013; · 1.42 Impact Factor
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    ABSTRACT: Adaptive tests are increasingly being used to assess health-related quality of life in patients with a variety of medical conditions, including osteoarthritis (OA) of the knee. This approach has recently been used to assess health state utility valuations (HSUV) for use in quality-adjusted life-year calculations. To accurately assess incremental value for money, these tools must be responsive. Therefore, we examined the responsiveness of the Health Utilities Index mark 3 (HUI3) and Paper Adaptive Test-5D (PAT-5DQOL) in a group of patients with knee OA. We used patient-level data from a randomized controlled trial evaluating a pharmacist-initiated multidisciplinary intervention in newly diagnosed patients with knee OA. The mean change for utility scores from baseline to 6 months was calculated, as well as effect size (ES) and standardized response mean (SRM) for the HUI3 and PAT-5DQOL, and generalized additive model plots, using the Western Ontario and McMaster Osteoarthritis index as a reference standard. When patients were assessed based on whether their condition had improved, remained unchanged, or worsened over time, the PAT-5DQOL showed greater responsiveness in patients whose condition had either improved or worsened. ES and SRM were generally small for both instruments. The PAT-5DQOL is more responsive to change over time than the HUI3 in patients with knee OA.
    The Journal of Rheumatology 11/2013; · 3.26 Impact Factor
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    ABSTRACT: Knee injuries can lead to radiographic osteoarthritis (ROA). Injuries may be "specific" (SI) including ligament or meniscal tears or patellar trauma, or "nonspecific" (NSI). Our objective is to understand the effect of knee NSI on ROA incidence and progression. 163 people (sample-weighted for population representativeness) aged 40+ with history of knee pain had radiographs assessed on Kellgren Lawrence (KL) grade (0/1 collapsed) at baseline and follow-up (median 3.2 years apart). Progression was an increase in KL score. SIs and NSIs were labeled "severe" (walking aid for >=1 week) or "moderate". One model treated SI and NSI as dichotomous (yes/no), and another as trichotomous (none/moderate/severe). Models were adjusted for age, sex, BMI, KL grade and follow-up time. SI/NSI history was none, moderate (7.8/24.4%) or severe (11.0/10.8%). Duration at baseline since SI/NSI ranged from <1 year to several decades (SI/NSI mean 4.6/6.5 years). SI was significantly associated with ROA incidence and progression (odds ratio (OR) = 2.90; 95% CI = 1.04, 8.09), but NSI showed no significant effect (OR = 1.36; 95% CI = 0.61, 3.02). In the trichotomous model, severe SI was significant (OR = 4.35, 95% CI = 1.26, 15.02), while moderate SI was not (OR = 1.51, 95% CI = 0.33, 6.84). NSI showed no effect: moderate OR = 1.51, 95% CI = 0.61, 3.74; severe OR = 0.90, 95% CI = 0.24, 3.40. This study had 80% power to detect an NSI OR of 2.9. We find no evidence that history of NSI affects knee ROA incidence and progression in a population with knee pain, adjusting for SI, age, sex, BMI, KL grade and follow-up time.
    BMC Musculoskeletal Disorders 10/2013; 14(1):309. · 1.88 Impact Factor
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    ABSTRACT: Objective: Our objective was to determine the risk of cardiovascular disease (CVD) among osteoarthritis (OA) patients using population-based administrative data from British Columbia, Canada. Methods: The medical history of a random sample of 600,000 individuals from years 1991 to 2009 were analyzed. 12,745 OA cases and up to 3 non-OA individuals matched by age, sex, and year of diagnosis were followed for CVD events. Cox proportional hazards and Poisson regression models were used to estimate the relative risks (RR) of CVD, myocardial infarction (MI), ischemic heart disease (IHD), congestive heart failure (CHF), and stroke after adjusting for available socio-demographic and medical factors. Results: OA was an independent predictor of CVD. The adjusted RRs (95% CI) were 1.15 (1.04-1.27), 1.26 (1.13- 1.42), and 1.17 (1.07-1.26) among older men, younger women, and older women, respectively. Analyses were stratified by age and sex due to statistically significant interactions between OA and age and sex. RRs (95% CI) among older men, younger women, and older women, respectively, were 1.33 (1.11-1.62), 1.66 (1.37-2.01), and 1.45 (1.22-1.72) for IHD, and 1.25 (1.02-1.54), 1.29 (1.00-1.68), and 1.20 (1.03-1.39) for CHF. Compared to no-OA individuals, OA cases underwent total joint replacements had a 26% increased risk of CVD. Conclusion: This prospective longitudinal study suggests that OA is associated with the increased risk of CVD. Older men and adult women with OA had a higher risk of CVD, particularly IHD and CHF. Further studies are needed to confirm these results and to elucidate the potential biological mechanisms. © 2013 American College of Rheumatology.
    Arthritis care & research. 08/2013;
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    ABSTRACT: Waitlists are commonly used in Canada to manage access to surgical procedures such as elective surgical lumbar discectomy (ESLD). The timing of enrollment onto the waitlist is important as this is a proxy measure for the concordance of preferences for surgery between a patient and surgeon. After enrollment, the waiting time to actual surgery extends the duration of preoperative symptoms, which possibly affects the outcome of ESLD. Waiting time also specifically reflects the delay in service delivery imposed by the limited capacity of the health-care system. To determine if a system-imposed delay in treatment, that is, longer waiting time, for ESLD is associated with a higher odds of experiencing residual postoperative pain. Ambidirectional cohort study with 2-year retrospective and 3-year prospective components, conducted at a major tertiary care center serving a metropolitan area in Canada. Patients aged 16 years or older with sciatica because of herniated lumbar disc, confirmed on advanced imaging, were recruited at the time of waitlist enrollment for ESLD. Patients with significant comorbidity or emergency indications for surgery were excluded. Of 391 participants, 291 had complete follow-up information at 6 months postoperatively. Intensity of the predominant symptom (worse of either back or leg pain) was assessed on the 11-point numerical rating scale at waitlist enrollment and 6 months postoperatively. Pain scores were highly skewed and therefore categorized into four ordinal levels defined by quartiles. For the primary analysis, time to surgery from waitlist enrollment was dichotomized based on a predetermined clinically meaningful cut-point of 12 weeks. Ordinal logistic regression was used to compare the odds of experiencing higher pain intensity between wait groups. Control of confounders was achieved using both propensity scores and conventional multivariable modeling. In unadjusted analyses, long-wait patients were 80% more likely than short-wait patients to experience higher ordinal pain intensity at 6 months; unadjusted proportional odds ratio (POR)=1.8 (95% confidence interval [CI], 1.2-2.8). The association held after controlling for all imbalances in measured confounders, with long-wait patients still being 70% more likely to report worse pain; adjusted POR=1.7 (95% CI, 1.0-2.8). A waiting time of 12 weeks or more after waitlist enrollment for ESLD is associated with a modest likelihood of experiencing worse pain at 6 months postoperatively. This result was not because of differences in measured confounders. Future studies are encouraged to identify other, as-of-yet unmeasured, variables that might be associated with both longer waiting times and worse outcomes among ESLD patients. Until then, in jurisdictions where highly constrained access to ESLD is managed through waitlists, the expected waiting time for the operation could be an informative deciding criterion for patients with otherwise unresolved preferences for operative treatment.
    The spine journal: official journal of the North American Spine Society 07/2013; · 2.90 Impact Factor
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    ABSTRACT: Objective To compare the incidence and progression of radiographic osteoarthritis (OA) in the knee and hip among African Americans and whites. Methods Using the joint as the unit of analysis, we analyzed data from the Johnston County Osteoarthritis Project, a population-based prospective cohort study in rural North Carolina. Baseline and followup assessments were 3–13 years apart. Assessments included standard knee and hip radiographs read for Kellgren/Lawrence (K/L) radiographic grade. Weighted analyses controlled for age, sex, body mass index, level of education, and baseline K/L grade; bootstrap methods adjusted for lack of independence between left and right joints. Time-to-event analysis was used to analyze the data. ResultsFor radiographic knee OA, being African American had no association with incidence (adjusted hazard ratio [HRadj] 0.80, 95% confidence interval [95% CI] 0.53–1.22), but had a positive association with progression (HRadj 1.67, 95% CI 1.05–2.67). For radiographic hip OA, African Americans had a significantly lower incidence (HRadj 0.44, 95% CI 0.27–0.71), whereas the association with progression was positive but nonsignificant (HRadj 1.46, 95% CI 0.53–4.01). In sensitivity analyses, the association with hip OA incidence was robust to a wide range of assumptions. Conclusion African Americans are protected against incident hip OA, but may be more susceptible to progressive knee OA.
    Arthritis Care & Research. 06/2013; 65(6).
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    ABSTRACT: OBJECTIVES: To develop a paper-and-pencil semi-adaptive test for 5 domains of health-related quality of life (PAT-5D-QOL) based on item response theory (IRT). METHODS: The questionnaire uses items from previously developed item banks for 5 domains: (1) walking, (2) handling objects, (3) daily activities, (4) pain or discomfort, and (5) feelings. For each domain, respondents are initially classified into 4 functional levels. Depending on the level, they are instructed to respond to a different set of 5 additional questions. IRT scores for each domain and overall health utility scores are obtained using a simple spreadsheet. The questions were selected using psychometric and conceptual criteria. The format of the questionnaire was developed through focus groups and cognitive interviews. Feasibility was tested in two population surveys. A simulation study was conducted to compare PAT-5D-QOL with a computerized adaptive test (CAT-5D-QOL) and a fixed questionnaire, developed from the same item banks, in terms of accuracy, bias, precision, and ceiling and floor effects. RESULTS: Close to 90 % of the participants in feasibility studies followed the skip instructions properly. In a simulation study, scores on PAT-5D-QOL for all domains tended to be more accurate, more precise, less biased, and less affected by a ceiling effect than scores on a fixed IRT-based questionnaire of the same length. PAT-5D-QOL was slightly inferior to a fully adaptive instrument. CONCLUSIONS: PAT-5D-QOL is a novel, semi-adaptive, IRT-based measure of health-related quality of life with a broad range of potential applications.
    Quality of Life Research 05/2013; · 2.41 Impact Factor
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    The 10th International Congress on SLE: Lupus 2013, Buenos Aires, Argentina; 04/2013
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    ABSTRACT: Practice guidelines emphasize the use of exercise and weight reduction as the first line of management for knee osteoarthritis (OA). However, less than half of the people with mild OA participate in moderate intensity physical activity. Given that physical activities have been shown to reduce pain, improve quality of life, and have the potential to reduce the progression of joint damage, many people with OA are missing the benefits of this inexpensive intervention. The objectives of this study are (1) to develop a behavioral theory-informed Internet intervention called Osteoarthritis Physical Activity & Exercise Net (OPEN) for people with previously undiagnosed knee OA, and (2) to assess the efficacy of the OPEN website for improving physical activity participation through a proof-of-concept study. OPEN was developed based on the theory of planned behavior. Efficacy of this online intervention is being assessed by an ongoing proof-of-concept, single-blind randomized controlled trial in British Columbia, Canada. We are currently recruiting participants and plan to recruit a total of 252 sedentary people with previously undiagnosed knee OA using a set of validated criteria. Half of the participants will be randomized to use OPEN and receive an OA education pamphlet. The other half only will receive the pamphlet. Participants will complete an online questionnaire at baseline, 3 months, and 6 months about their participation in physical activities, health-related quality of life, and motivational outcomes. In addition, we will perform an aerobic fitness test in a sub-sample of participants (n=20 per study arm). In the primary analysis, we will use logistic regression to compare the proportion of participants reporting being physically active at or above the recommended level in the 2 groups, adjusting for baseline measurement, age, and sex. This study evaluates a theory-informed behavioral intervention at a time when people affected with OA tend to be more motivated to adopt an active lifestyle (ie, at the early stage of OA). Our approach, which consisted of the identification of early knee OA followed immediately by an online intervention that directly targets physical inactivity, can be easily implemented across communities. Our online intervention directly targets physical inactivity at a time when the joint damage tends to be mild. If OPEN is found to be effective in changing long-term physical activity behaviors, it opens further opportunities to promote early diagnosis and to implement lifestyle interventions. Clinicaltrial.gov: NCT01608282; http://clinicaltrials.gov/ct2/show/NCT01608282 (Archived by WebCite at http://www.webcitation.org/6G7sBBayI).
    JMIR research protocols. 01/2013; 2(1):e17.
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    ABSTRACT: OBJECTIVES: Our objective was to determine the relationship between osteoarthritis (OA) and heart diseases (myocardial infarction (MI), angina, congestive heart failure (CHF)) and stroke using population-based survey data. DESIGN: Cross-sectional study. SETTING: Canadian Community Health Survey (CCHS). PARTICIPANTS: Adult participants in the CCHS cycles 1.1, 2.1 and 3.1 were included. CCHS provides nationally representative data on health determinants, health status and health system utilisation. We have identified 40 817 self-reported OA subjects and selected 1:1 matched non-OA respondents by age, sex and CCHS cycles. MAIN OUTCOME MEASURES: Self-reported heart disease was the primary outcome and MI, angina, CHF and stroke were considered as secondary outcomes. Multivariable logistic regression models were used to estimate the ORs after adjusting for sociodemographic status, obesity, physical activity, smoking status, fruit and vegetable consumption, medication use, diabetes, hypertension and chronic obstructive pulmonary disease. RESULTS: The mean age of OA cases was 66 years and 71.6% were women. OA exhibited increased odds of prevalent heart disease, and adjusted overall OR (95% CI) was 1.45 (1.36 to 1.54), 1.35 (1.21 to 1.50) among men and 1.51 (1.39 to 1.64) among women with OA. OA showed increased ORs for angina and CHF in both men and women, and for MI in women. ORs (95% CI) for men and women, respectively, were 1.08 (0.91 to 1.28) and 1.49 (1.28 to 1.75) for MI, 1.76 (1.43 to 2.17) and 1.84 (1.59 to 2.14) for angina, 1.50 (1.13 to 1.97) and 1.81 (1.49 to 2.21) for CHF, and 1.08 (0.83 to 1.40) and 1.13 (0.93 to 1.37) for stroke. CONCLUSIONS: Prevalent OA was associated with self-reported heart disease, particularly angina, and CHF in both men and women, after controlling for established risk factors for these conditions. This study provides a rationale for further investigation of the association between OA and heart disease in longitudinal studies for investigating possible biological and behavioural mechanisms.
    BMJ Open 01/2013; 3(5). · 1.58 Impact Factor
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    American College of Rheumatology/ Association of Rheumatology Health Professionals, Washington, DC; 11/2012
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    ABSTRACT: Objective. Administrative data are increasingly being used for research and surveillance about rheumatic diseases. However, literature reviews have revealed a lack of consistency in methods for conducting observational rheumatic disease studies, a situation that can lead to findings that cannot be compared. Our purpose was to develop best-practice consensus statements about the use of administrative data for rheumatic disease research and surveillance in Canada. Methods. We convened 52 decision makers, epidemiologists, clinicians, and researchers to a 2-day workshop. Prior to this, participants formed working groups to examine 3 best-practice categories: case definitions, epidemiology methods, and comorbidity and outcomes measurement. The groups conducted systematic or scoping reviews on key topics. At the workshop, evidence from the reviews was presented and consensus-building techniques were used to develop the best-practice statements. The statements were presented, discussed, revised (as needed), and then subjected to voting. Results. Thirteen best-practice consensus statements were developed and endorsed by consensus. For the first category, these consensus statements addressed validation techniques for rheumatic disease case definitions and case ascertainment bias. The consensus statements for epidemiology methods focused on confounding and drug exposure measurement. For comorbidity and outcomes measurement, consensus statements were developed for multiple conditions, including osteoporosis and fragility fractures, cancer, infections, cardiovascular disease, and renal disease. Strengths and limitations of administrative data were identified in relation to each topic. Conclusion. Our best-practice consensus statements are consistent with other recent guidelines, including those for rheumatic disease biologics registries, but address additional issues specific to administrative data. Continuing work focuses on disseminating these consensus statements to multiple audiences.
    The Journal of Rheumatology 11/2012; 4040:66-73. · 3.26 Impact Factor
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    ABSTRACT: To evaluate the measurement properties of an Internet-based self-administered questionnaire in ascertaining cases of hip and knee osteoarthritis (OA). Questionnaire data from 4269 Canadian subjects aged 45-85 were collected on hip and knee joint health including self-reported items on medically-diagnosed hip and knee OA and joint replacement. A sub-cohort of 100 subjects was recruited for clinical examination. The self-reported outcomes were evaluated using the American College of Rheumatology clinical classification criteria for hip and knee OA as the gold standard for clinical verification. Analysis was at the joint level (200 knees, 200 hips). Validity was examined using sensitivity, specificity, and predictive values; to account for correlated joints of the same subject, bootstrapping was performed to yield valid 95% confidence interval (CI's). Self-reported measures for a medical diagnosis of knee OA had a positive predictive value of 86%, negative predictive value 91%, sensitivity 73% and specificity 96% for correctly identifying clinical knee OA. For hip OA, the values were 61%, 98%, 81% and 94% respectively. Internet self-report of medically-diagnosed hip and knee OA in metro Vancouver residents correctly identified most cases and non-cases of clinical OA when compared with the ACR clinical classification criteria gold standard. In particular, specificity was very high, important in risk factor studies due to the profound effect of even small losses in specificity on the measure of association. The findings provide evidence that these questionnaire case definitions have utility for identifying hip and knee OA in community and population-based studies when the purpose is to link potential risk factors with knee and hip health.
    Osteoarthritis and Cartilage 09/2012; 20(12):1568-73. · 4.26 Impact Factor
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    Arthritis Research & Therapy 09/2012; 14(3). · 4.30 Impact Factor
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    ABSTRACT: BACKGROUND: The impact of arm morbidity following breast cancer surgery on patient-observed changes in daily functioning and health-related quality of life (HRQoL) has not been well-studied. OBJECTIVE: To examine the association of objective measures such as range of motion (ROM) and lymphedema, with patient-reported outcomes (PROs) in the arm and breast, upper extremity function, activities, and HRQoL. METHODS: The National Surgical Adjuvant Breast and Bowel Project Protocol B-32 was a randomized trial comparing sentinel node resection (SNR) with axillary dissection (AD) in women with node-negative breast cancer. ROM and arm volume were measured objectively. PROs included symptoms; arm function; limitations in social, recreational, occupational, and other regular activities; and a global index of HRQoL. Statistical methods included cross-tabulations and multivariable linear regression models. RESULTS: In all, 744 women provided at least 1 postsurgery assessment. About one-third of the patients experienced arm mobility restrictions. A similar number of patients avoided the use of the arm 6 months after surgery. Limitations in work and other regular activities were reported by about a quarter of the patients. In this multivariable analysis, arm mobility and sensory neuropathy were predictors of patient-reported arm function and overall HRQoL. Predictors for activity limitations also included side of surgery (dominant vs nondominant). Edema was not significant after adjustment for sensory neuropathy and ROM. LIMITATIONS: Arm mobility and edema were measured simultaneously only once during the follow-up (6 months). CONCLUSION: Clinical measures of sensory neuropathy and restrictions in arm mobility following breast cancer surgery are associated with self-reported limitations in activity and reductions in overall HRQoL.
    The journal of supportive oncology 08/2012;
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    ABSTRACT: Objective. Uncertainty analysis (UA) is an important part of simulation model validation. However, literature is imprecise as to how UA should be performed in the context of population-based microsimulation (PMS) models. In this expository paper, we discuss a practical approach to UA for such models. Methods. By adapting common concepts from published UA guidelines, we developed a comprehensive, step-by-step approach to UA in PMS models, including sample size calculation to reduce the computational time. As an illustration, we performed UA for POHEM-OA, a microsimulation model of osteoarthritis (OA) in Canada. Results. The resulting sample size of the simulated population was 500,000 and the number of Monte Carlo (MC) runs was 785 for 12-hour computational time. The estimated 95% uncertainty intervals for the prevalence of OA in Canada in 2021 were 0.09 to 0.18 for men and 0.15 to 0.23 for women. The uncertainty surrounding the sex-specific prevalence of OA increased over time. Conclusion. The proposed approach to UA considers the challenges specific to PMS models, such as selection of parameters and calculation of MC runs and population size to reduce computational burden. Our example of UA shows that the proposed approach is feasible. Estimation of uncertainty intervals should become a standard practice in the reporting of results from PMS models.
    Epidemiology Research International. 07/2012; Volume 2012 (2012),(Article ID 610405):14 pages.
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    ABSTRACT: BACKGROUND: Neurotoxicity from adjuvant treatment with oxaliplatin has been studied in patients with colorectal carcinoma in short-term studies, but, to the authors' knowledge, the current article is the first long-term assessment which reports the National Surgical Adjuvant Breast and Bowel Project (NSABP) investigation of whether excess neurotoxicity persists beyond 4 years. METHODS: As part of a colorectal cancer long-term survivor study (LTS-01), long-term neurotoxicity was assessed in 353 patients on NSABP Protocol C-07 (cross-sectional sample). Ninety-two of these patients from LTS-01 also had longitudinal data and were reassessed 5 to 8 years (median, 7 years) after random assignment (longitudinal sample). Contingency tables compared cohorts, a mixed model compared neurotoxicity between treatments over time, and a Wilcoxon rank-sum test compared neurotoxicity between treatments (cross-sectional sample). RESULTS: In the cross-sectional sample, the increase in mean total neurotoxicity scores of 1.8 with oxaliplatin was statistically significant (P = .005), but not clinically significant (a minimally important difference of 4 was reported at the long-term assessment). Patients who received oxaliplatin had increased odds of numbness and tingling in hands (odds ratio, 2.00; P = .015) and feet (odds ratio, 2.78; P < .001) versus patients who did not receive oxaliplatin. The magnitude of the oxaliplatin effect varied with time (P < .001) in the longitudinal sample, such that the oxaliplatin-treated group did not have significantly greater total neurotoxicity scores by 7 years. CONCLUSIONS: At the long-term endpoint, there was no clinically significant increase in total neurotoxicity scores for patients who received oxaliplatin, but the specific neurotoxicities of numbness and tingling of the hands and feet remained significantly elevated for oxaliplatin-treated patients. Cancer 2012. © 2012 American Cancer Society.
    Cancer 05/2012; · 5.20 Impact Factor

Publication Stats

2k Citations
434.93 Total Impact Points

Institutions

  • 2001–2014
    • University of British Columbia - Vancouver
      • • Department of Medicine
      • • School of Population and Public Health
      • • Faculty of Medicine
      • • Department of Orthopaedics
      Vancouver, British Columbia, Canada
  • 2001–2013
    • Arthritis Research Centre of Canada
      Richmond, British Columbia, Canada
  • 2012
    • Brigham and Women's Hospital
      • Division of Rheumatology, Immunology, and Allergy
      Boston, MA, United States
  • 2004–2012
    • University of Pittsburgh
      • Department of Biostatistics
      Pittsburgh, PA, United States
    • The Arthritis Society
      Toronto, Ontario, Canada
  • 2011
    • University of Manitoba
      • Faculty of Medicine
      Winnipeg, Manitoba, Canada
    • St. Paul's Hospital
      Saskatoon, Saskatchewan, Canada
  • 2010–2011
    • Trinity Western University
      • School of Nursing
      Langley, British Columbia, Canada
  • 2009–2010
    • Vancouver General Hospital
      Vancouver, British Columbia, Canada
    • Simon Fraser University
      • Department of Statistics and Actuarial Sciences
      Burnaby, British Columbia, Canada
  • 2003
    • Toronto Rehabilitation Institute
      Toronto, Ontario, Canada
  • 2000–2003
    • Institute for Clinical Evaluative Sciences
      Toronto, Ontario, Canada
  • 1998
    • University of Toronto
      Toronto, Ontario, Canada
  • 1990–1996
    • McGill University
      • Department of Medicine
      Montréal, Quebec, Canada