[Show abstract][Hide abstract] ABSTRACT: The POpulation HEalth Model (POHEM) is a health microsimulation model that was developed at Statistics Canada in the early 1990s. POHEM draws together rich multivariate data from a wide range of sources to simulate the lifecycle of the Canadian population, specifically focusing on aspects of health. The model dynamically simulates individuals' disease states, risk factors, and health determinants, in order to describe and project health outcomes, including disease incidence, prevalence, life expectancy, health-adjusted life expectancy, quality of life, and healthcare costs. Additionally, POHEM was conceptualized and built with the ability to assess the impact of policy and program interventions, not limited to those taking place in the healthcare system, on the health status of Canadians. Internationally, POHEM and other microsimulation models have been used to inform clinical guidelines and health policies in relation to complex health and health system problems. This paper provides a high-level overview of the rationale, methodology, and applications of POHEM. Applications of POHEM to cardiovascular disease, physical activity, cancer, osteoarthritis, and neurological diseases are highlighted.
Population Health Metrics 09/2015; 13(1):24. DOI:10.1186/s12963-015-0057-x · 2.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective
To determine the association of body mass index (BMI) with incidence and progression of knee effusion on magnetic resonance imaging (MRI) and physical examination (PE) in a longitudinal cohort with knee pain.MethodsA population-based cohort was assessed at baseline and 3 years (N=163). BMI was categorized: normal (<25), overweight (25–29.9), obese (≥30). Knee effusion was graded 0-3 (absent/mild/moderate/severe) on MRI and 0-1 (absent/present) on PE. Progression of MRI effusion (MRIeff) was an increase of ≥1 grade in those with grade 1 or 2 at baseline. Incident MRIeff and PE effusion (PEeff) are any effusion at follow-up (>0) in those with grade 0 at baseline. A second type of incident MRIeff was effusion grade ≥2 at follow-up in those with grade <2 at baseline. Exponential regression analysis was used, adjusted for age, sex and radiographic severity.ResultsIncident MRIeff≥1, incident MRIeff≥2, incident PEeff, and progression of MRIeff were seen in 14/73 (19%), 18/140 (13%), 26/127 (20%) and 18/86 (21%), respectively. There was a borderline statistical association of obesity with progression of MRIeff (HR 3.3, 95%CI 1.0-11.2) and with incident MRIeff≥2 (HR 3.4, 95%CI 1.0-11.5). BMI was not associated with incident MRIeff≥1 (HR [95%CI] overweight: 1.1 [0.3-3.6]; obese 1.0 [0.2-5.0]). Overweight was associated with incident PEeff (HR 4.5, 95%CI 1.4-14.2), while obesity was not statistically significant (HR 3.1, 95%CI 0.9-11.1).Conclusion
Obesity was a risk factor for incident and progressive knee effusion in this population-based cohort. These findings highlight an important link between obesity and inflammation in knee OA. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Background Femoroacetabular impingement (FAI) and physical activity involving hip flexion have been suggested as key risk factors for hip pain among young and middle-aged individuals  but population studies have been lacking.
Objectives To determine if physical activity involving hip flexion is a risk factor for persistent or recurrent hip pain in young and middle-aged persons with and without FAI.
Methods A population sample of persons aged 20-49 with (cases) and without (controls) hip pain in Metro Vancouver, Canada, was selected through random digit dialing. Hip pain was defined as pain in the groin or upper thigh in the past 12 months that lasted 6 weeks or longer or occurred on 3 or more occasions. Subjects completed a lifetime physical activity questionnaire including domestic, occupational and sports/recreational activities. Flexion scores were calculated from reported total hours of activities involving hip flexion>70 degrees (e.g., squatting, kneeling, skiing, rowing, but excluding sitting). Data on peak hip flexion for various activities were derived from the literature. Standardized X-rays of the pelvis/hips with AP and Dunn views were obtained. FAI was defined as one or more of the following: lateral centre edge angle (LCE) >40°, alpha angle >55° and positive cross-over sign. We analyzed the relationship between flexion scores and hip pain among persons with and without FAI using logistic regression. In secondary analyses we a) used hip (rather than person) as the unit of analysis; b) considered only activities prior to the onset of pain. Odds ratios (OR) are reported for a one standard deviation difference in flexion scores.
Results Data were obtained for 500 subjects, 269 cases and 231 controls. Mean age was 43 years in both groups, 34% of the cases and 39% of the controls were male. Prevalence of radiographic FAI was 49% in the cases and 43% in the controls. Mean (SD, range) flexion scores were 78 (126, 0-1074) in the cases and 60 (112, 0-782) in the controls for work/domestic activities, and 25 (37, 0-198) and 24 (48, 0-306) for sports activities, respectively. After adjusting for age and sex, a higher flexion score for work/domestic activities was associated with hip pain in subjects with FAI (OR=1.54, 1.01-2.35) but not in those without FAI (OR=1.10, 0.89-1.36). For sports/recreational activities, flexion score was not significantly associated with pain in either group (OR=0.90, 0.71-1.14 and OR=1.25, 0.93-1.68 for those with and without FAI, respectively). The hip-based analysis and the analysis limited to activities prior to the onset of pain showed similar results.
Conclusions A one SD increase in the frequency of domestic and work-related activities involving hip flexion is associated with a 50% increase in the risk of persistent or recurrent hip pain in young and middle-aged persons with radiographic FAI. This finding may help understand the causes of hip osteoarthritis.
Acknowledgements The study was supported by a grant from the Canadian Institutes of Health Research.
Disclosure of Interest None declared
Annals of the Rheumatic Diseases 06/2015; 74(Suppl 2):86.1-86. DOI:10.1136/annrheumdis-2015-eular.2053 · 10.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objectives:
The CAT-5D-QOL is a previously reported item response theory (IRT)-based computerized adaptive tool to measure five domains (attributes) of health-related quality of life. The objective of this study was to develop and validate a multiattribute health utility (MAHU) scoring method for this instrument.
Study design and setting:
The MAHU scoring system was developed in two stages. In phase I, we obtained standard gamble (SG) utilities for 75 hypothetical health states in which only one domain varied (15 states per domain). In phase II, we obtained SG utilities for 256 multiattribute states. We fit a multiplicative regression model to predict SG utilities from the five IRT domain scores. The prediction model was constrained using data from phase I. We validated MAHU scores by comparing them with the Health Utilities Index Mark 3 (HUI3) and directly measured utilities and by assessing between-group discrimination.
MAHU scores have a theoretical range from -0.842 to 1. In the validation study, the scores were, on average, higher than HUI3 utilities and lower than directly measured SG utilities. MAHU scores correlated strongly with the HUI3 (Spearman ρ = 0.78) and discriminated well between groups expected to differ in health status.
Results reported here provide initial evidence supporting the validity of the MAHU scoring system for the CAT-5D-QOL.
Journal of clinical epidemiology 04/2015; DOI:10.1016/j.jclinepi.2015.03.020 · 3.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objectives. Our aim was to determine the risk of diabetes among osteoarthritis (OA) cases in a prospective longitudinal study. Methods. Administrative health records of 577,601 randomly selected individuals from British Columbia, Canada, from 1991 to 2009, were analyzed. OA and diabetes cases were identified by checking physician's visits and hospital records. From 1991 to 1996 we documented 19,143 existing OA cases and selected one non-OA individual matched by age, sex, and year of administrative records. Poisson regression and Cox proportional hazards models were fitted to estimate the effects after adjusting for available sociodemographic and medical factors. Results. At baseline, the mean age of OA cases was 61 years and 60.5% were women. Over 12 years of mean follow-up, the incidence rate (95% CI) of diabetes was 11.2 (10.90-11.50) per 1000 person years. Adjusted RRs (95% CI) for diabetes were 1.27 (1.15-1.41), 1.21 (1.08-1.35), 1.16 (1.04-1.28), and 0.99 (0.86-1.14) for younger women (age 20-64 years), older women (age ≥ 65 years), younger men, and older men, respectively. Conclusion. Younger adults and older women with OA have increased risks of developing diabetes compared to their age-sex matched non-OA counterparts. Further studies are needed to confirm these results and to elucidate the potential mechanisms.
International Journal of Rheumatology 11/2014; 2014:620920. DOI:10.1155/2014/620920
[Show abstract][Hide abstract] ABSTRACT: Identifying persons with early rheumatoid arthritis (RA) is a major challenge. The role of the Internet in making decisions about seeking care has not been studied. We developed a method for early diagnosis and referral using the Arthritis Foundation's website. A person with less than 3 months of joint pain symptom who has not yet sought medical attention was screened. Prescreened persons are linked to a self-scoring questionnaire and get a "likelihood" of RA statement. If "likely," the person is offered a free evaluation and biomarker testing performed by Quest Diagnostics. The system available only to Massachusetts's residents yielded a small steady flow of screen-positive individuals. Over 21 months, 43,244 persons took the Arthritis Foundation website prescreening questionnaire; 196 were from Massachusetts and 60 took the self-scoring algorithm. Of the 48 who screened positive, 29 set up an appointment for a free evaluation, but six never came in. Twenty-four subjects were evaluated and diagnosed independently by three rheumatologists. One met the 1987 American College of Rheumatology (ACR) criteria for RA and two met the 2010 ACR/EULAR RA criteria. The 24 examined individuals were contacted at a minimum of 1 year and asked to redo the case-finding questionnaire and asked about their health resource utilization during the interval. Seventeen of the 24 subjects responded, and 10 had seen a health professional. Three of the 17 had a diagnosis of RA; all were on at least methotrexate. Internet case finding was useful in identifying new potential RA cases. The system's performance characteristics are theoretically limited only by the number of study sites available. However, the major barrier may be that seeing a health professional is not a priority for many individuals with early symptoms.
[Show abstract][Hide abstract] ABSTRACT: Background Gestational Diabetes Mellitus (GDM) is a common health problem among pregnant women and may be associated with distress. Purpose The purpose of the study was to describe changes in patient-reported outcomes in women with GDM and identify factors associated with increased distress in these patients. Research Design The study was conducted in 205 women diagnosed with GDM. Study participants underwent a physical examination and completed a questionnaire two times during pregnancy. On average, the questionnaire was completed at 27 weeks of gestation at baseline and 36 weeks at follow-up. The questionnaire included socio-demographic and clinical variables, standardized patient-reported outcome measures, and questions about the impact of GDM on daily life, satisfaction with care, knowledge about GDM, and social and professional support. Our main outcome of interest was diabetes-related distress, measured by the Problem Areas in Diabetes (PAID) questionnaire. Data were analyzed using descriptive statistics and multivariable regression models. Results At baseline, 80 % of the women were satisfied with their diabetes care and 58 % said they managed their diabetes well. The proportion reporting little or no knowledge of GDM dropped from almost 50 % at baseline to 14 % at follow-up. However, the proportion reporting that GDM affected their social life increased from 26 to 35 %, and the proportion reporting interference with family life increased from 14 to 26 %. Insulin treatment, frequency of blood glucose measurements, lack of knowledge about GDM, and lack of support from family and health care providers were strongly and significantly associated with distress. Conclusion In women with GDM, intensified treatment and lack of informational and social support are associated with distress. These aspects of GDM care appear to be appropriate targets for future research and interventions aimed at reducing the level of distress in these patients.
International Journal of Behavioral Medicine 08/2014; 22(2). DOI:10.1007/s12529-014-9428-0 · 2.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective:
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.
Twenty subjects suspected of having LLD participated in this study. Two clinical methods, 1 direct using a tape measure and 1 indirect using lifts, were standardized and carried out by 4 examiners. Difference in height of the femoral heads on standing pelvic radiograph was measured and served as the gold standard.
The intraclass correlation coefficient assessing interobserver reliability was 0.737 for lifts and 0.477 for tape measure. The remainder of the analysis is based on the average of the measurements by the 4 examiners. Pearson correlation coefficients were 0.93 for the lifts and 0.75 for the tape measure method. Paired sample t tests showed difference in means of 2 mm (p = 0.051) for lifts and -5 mm (p = 0.007) for tape measure compared with radiograph. Sensitivity and specificity were 55% and 89% for lifts and 45% and 56% for tape measure, respectively, using > 5 mm as the definition for LLD. The wrong leg was identified as being shorter in 1 out of 20 subjects using lifts versus 7 out of 20 using tape measure.
The indirect standing method of LLD measurement using lifts had superior validity, interobserver reliability, and specificity in comparison with radiograph over the direct supine method using tape measure. Both clinical methods underestimated LLD compared with radiograph.
The Journal of Rheumatology 07/2014; 41(8). DOI:10.3899/jrheum.131089 · 3.19 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background Bone marrow lesions (BML) occur commonly in knee osteoarthritis (OA) and may be a target for intervention in randomized controlled trials. The potential benefit of therapeutic interventions in OA is likely enhanced if aimed at early stage disease. We have previously shown that knee effusion is associated with cartilage damage in early knee OA, but it is unknown whether knee effusion is associated with BML in early disease.
Objectives To evaluate whether knee effusion on physical examination is associated with prevalent BML and with progression of BML over 3 years.
Methods Population-based longitudinal cohort study of subjects, age 40-79, with knee pain. Subjects were evaluated at baseline and follow-up (mean 3.2 years) using standardized knee examination, fixed-flexion knee radiographs and MRI (1.5T). Only subjects with Kellgren-Lawrence (KL) radiographic grade 0-2 were included in this analysis. Knee effusion on examination was scored as present or absent. BML was scored on MRI on a 0-3 scale at 6 joint sites and the maximum score at any site was used in the analysis. Progression of BML was defined as worsening by ≥1 grade in those with BML 0-2 at baseline. Due to small numbers incidence and progression of BML could not be evaluated separately. MRI was read semi-quantitatively for cartilage damage (0-4 scale). Logistic regression analysis was used to evaluate the association of baseline knee effusion with BML prevalence and with BML progression. Analyses were adjusted for age, sex and body mass index.
Results At baseline (n=199), mean age was 56 years, 50% were female and 16% had a knee effusion. KL grade 0, 1 and 2 was present in 50%, 28% and 22%, respectively. Cartilage damage on MRI was seen in 88%. BML was present in 79/199 subjects (40%). Of those with BML, 23/79 (29.1%) had effusion, compared to those without BML, where 8/120 (6.7%) had effusions. Knee effusion on examination was significantly associated with prevalent BML (OR 5.41, 95% CI 2.20-13.28). In this model, age was also significant with the risk of BML increased in those aged ≥50 years, compared to those aged 40-49 (OR 3.33, 95% CI 1.65-6.70). At follow-up (n=124), progression of BML was seen in 25/124 subjects (20.2%). Of these, 9/72 (12.5%) progressed from BML 0 to higher grades, while 16/52 (30.8%) progressed from BML 1 or 2 to higher grades. Baseline knee effusion was associated with a significant risk of progression of BML at 3 years (OR 3.02, 95% CI 1.01-9.01).
Conclusions In this population-based cohort of early knee OA, the risk of prevalent BML and the risk of BML progression were both significantly increased in those with effusion compared to those without effusion on knee examination at baseline. Whether effusion is related to BML progression through common inflammatory signals or through other mechanisms requires further study. Evaluation for knee effusion may be a useful and inexpensive clinical test for potential identification of subjects with BML in clinical trials.
Disclosure of Interest : None declared
Annals of the Rheumatic Diseases 06/2014; 73(Suppl 2):259-259. DOI:10.1136/annrheumdis-2014-eular.4840 · 10.38 Impact Factor
[Show abstract][Hide abstract] 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; 41(6). DOI:10.3899/jrheum.131011 · 3.19 Impact Factor
[Show abstract][Hide abstract] 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.
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.
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.
Baseline subchondral sclerosis as detected by MRI did not increase the risk of cartilage loss over time.
Osteoarthritis and Cartilage 04/2014; 22(4). DOI:10.1016/j.joca.2014.01.006 · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to evaluate the validity and reliability of a radiographic diagnosis of femoroacetabular impingement (FAI) by a non-radiologist. Symptomatic FAI is prevalent and thought to be a cause of hip osteoarthritis. However, the diagnosis is often delayed by 1-2 years, in large part because radiographic findings are often subtle and clinicians have been unaware of their significance. The purpose of this study was to evaluate the validity of a radiographic diagnosis of FAI by a non-radiologist. A population-based sample of 701 subjects was recruited in Vancouver, Canada. For the current study, 50 subjects were selected-40 randomly from the population sample and 10 from an orthopedic practice with confirmed FAI. An anterior-posterior pelvis and bilateral Dunn radiographs were acquired and read by a fellowship-trained musculoskeletal radiologist and a third-year medical student who received basic training in radiographic signs of FAI. Three radiographic signs were evaluated: the lateral center edge angle, alpha angle and crossover sign. Validity was assessed using sensitivity and specificity, Bland-Altman limits of agreement and kappa. The sample contained 65 % women (n = 31), was 62 % Caucasian and 38 % Chinese and had a mean age of 38.3 years. For correctly diagnosing FAI, the non-radiologist reader had a sensitivity of 0.83 and specificity of 0.87. Intra-rater κ value was 0.72, and prevalence-adjusted bias-adjusted κ was 0.76. This study provides evidence that a non-radiologist can accurately and reliably identify FAI on plain films.
Osteoarthritis and Cartilage 04/2014; 22:S270-S271. DOI:10.1016/j.joca.2014.02.508 · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background Severity of knee malalignment is a risk factor for osteoarthritis (OA) progression. Currently the hip-knee-angle, assessed on a full-limb radiograph, is the gold standard. Direct measurement of the anatomic axis using standard knee radiographs has been validated as an alternative method (1).
Objectives The aim of the current study was to 1) evaluate the correlation of knee alignment angle measured by goniometer on physical examination with the anatomic angle measured on knee radiographs and 2) to evaluate whether the relationship is confounded by clinical variables that may affect goniometric measurements.
Methods A simple random sample was selected from the MoDEKO (Model for the Diagnosis of Early Knee Osteoarthritis) cohort, cohort of people with knee pain, age 40-79. Knee alignment was measured to the nearest degree by: 1) anatomic-axis on fixed-flexion PA knee radiographs and 2) standardized goniometer assessment on physical examination. Varus was defined as angle < 0, valgus > 0 and 0o as neutral. Anatomic axis was defined by the intersection of two lines originating from points bisecting the femur and tibia and converging at the centre of tibial spine tips. Inter- and intra-rater reliability of anatomic angle measurements from radiographs were determined by intraclass correlation coefficient (ICC) of two independent assessors. The correlation of radiographic anatomic angle with goniometer measurements was analyzed by linear regression. Western Ontario and McMaster Universities (WOMAC) pain score, body mass index (BMI) and flexion contracture were assessed as potential confounders. Analysis was weighted by stratum sampling weights.
Results Of 120 subjects, 52% were male, with mean (SD) age of 58 (11) years and BMI of 27 (5). The mean (SD) angle measured on PA radiographs and goniometer were 2 (3.6) and 3 (2.3) degrees respectively. Intra- and inter-rater ICC for radiographic measurements were 0.93 and 0.83 respectively. A significant correlation was found between radiographic and goniometer measurements (r = 0.48; P < 0.0001). A model was developed to predict anatomic angle based on goniometer angle: anatomic angle on PA radiographs = 0.410 + 0.749*goniometer angle. WOMAC pain score, BMI and flexion contracture were not significantly associated with PA radiographic angle and did not significantly change the correlation of radiographic and goniometric measurements, and were dropped from the model.
Conclusions In this study, knee alignment assessed by goniometer was significantly correlated with the anatomic axis angle on fixed-flexion PA knee radiographs. Moreover, factors such as pain, BMI and flexion contracture did not confound the relationship of goniometric with radiographic angle measurements. Given the ease of application, goniometric measurements may be preferable to x-ray, although the predictive utility of goniometric alignment measurement will require further assessment in longitudinal studies of knee OA.
Disclosure of Interest None Declared
Annals of the Rheumatic Diseases 01/2014; 72(Suppl 3):A695-A695. DOI:10.1136/annrheumdis-2013-eular.2056 · 10.38 Impact Factor