Guanmin Chen

Validation of a case definition to define hypertension using administrative data.

We validated the accuracy of case definitions for hypertension derived from administrative data across time periods (year 2001 versus 2004) and geographic regions using physician charts. Physician charts were randomly selected in rural and urban areas from Alberta and British Columbia, Canada, during years 2001 and 2004. Physician charts were linked with administrative data through unique personal health number. We reviewed charts of ≈50 randomly selected patients >35 years of age from each clinic within 48 urban and 16 rural family physician clinics to identify physician diagnoses of hypertension during the years 2001 and 2004. The validity indices were estimated for diagnosed hypertension using 3 years of administrative data for the 8 case-definition combinations. Of the 3362 patient charts reviewed, the prevalence of hypertension ranged from 18.8% to 33.3%, depending on the year and region studied. The administrative data hypertension definition of “2 claims within 2 years or 1 hospitalization” had the highest validity relative to the other definitions evaluated (sensitivity 75%, specificity 94%, positive predictive value 81%, negative predictive value 92%, and &kgr; 0.71). After adjustment for age, sex, and comorbid conditions, the sensitivities between regions, years, and provinces were not significantly different, but the positive predictive value varied slightly across geographic regions. These results provide evidence that administrative data can be used as a relatively valid source of data to define cases of hypertension for surveillance and research purposes.

Symptomatic in-hospital deep vein thrombosis and pulmonary embolism following hip and knee arthroplasty among patients receiving recommended prophylaxis: a systematic review

CONTEXT Symptomatic venous thromboembolism (VTE) after total or partial knee arthroplasty (TPKA) and after total or partial hip arthroplasty (TPHA) are proposed patient safety indicators, but its incidence prior to discharge is not defined. OBJECTIVE To establish a literature-based estimate of symptomatic VTE event rates prior to hospital discharge in patients undergoing TPHA or TPKA. DATA SOURCES Search of MEDLINE, EMBASE, and the Cochrane Library (1996 to 2011), supplemented by relevant articles. STUDY SELECTION Reports of incidence of symptomatic postoperative pulmonary embolism or deep vein thrombosis (DVT) before hospital discharge in patients who received VTE prophylaxis with either a low-molecular-weight heparin or a subcutaneous factor Xa inhibitor or oral direct inhibitor of factors Xa or IIa. DATA EXTRACTION AND SYNTHESIS Meta-analysis of randomized clinical trials and observational studies that reported rates of postoperative symptomatic VTE in patients who received recommended VTE prophylaxis after undergoing TPHA or TPKA. Data were independently extracted by 2 analysts, and pooled incidence rates of VTE, DVT, and pulmonary embolism were estimated using random-effects models. RESULTS The analysis included 44,844 cases provided by 47 studies. The pooled rates of symptomatic postoperative VTE before hospital discharge were 1.09% (95% CI, 0.85%-1.33%) for patients undergoing TPKA and 0.53% (95% CI, 0.35%-0.70%) for those undergoing TPHA. The pooled rates of symptomatic DVT were 0.63% (95% CI, 0.47%-0.78%) for knee arthroplasty and 0.26% (95% CI, 0.14%-0.37%) for hip arthroplasty. The pooled rates for pulmonary embolism were 0.27% (95% CI, 0.16%-0.38%) for knee arthroplasty and 0.14% (95% CI, 0.07%-0.21%) for hip arthroplasty. There was significant heterogeneity for the pooled incidence rates of symptomatic postoperative VTE in TPKA studies but less heterogeneity for DVT and pulmonary embolism in TPKA studies and for VTE, DVT, and pulmonary embolism in TPHA studies. CONCLUSION Using current VTE prophylaxis, approximately 1 in 100 patients undergoing TPKA and approximately 1 in 200 patients undergoing TPHA develops symptomatic VTE prior to hospital discharge.

Cardiovascular Outcomes in Framingham Participants With Diabetes: The Importance of Blood Pressure

We designed this study to explore to what extent the excess risk of cardiovascular events in diabetic individuals is attributable to hypertension. We retrospectively analyzed prospectively collected data from the Framingham original and offspring cohorts. Of the 1145 Framingham subjects newly diagnosed with diabetes mellitus who did not have a previous history of cardiovascular events, 663 (58%) had hypertension at the time that diabetes mellitus was diagnosed. During 4154 person-years of follow-up, 125 died, and 204 experienced a cardiovascular event. Framingham participants with hypertension at the time of diabetes mellitus diagnosis exhibited higher rates of all-cause mortality (32 versus 20 per 1000 person-years; P<0.001) and cardiovascular events (52 versus 31 per 1000 person-years; P<0.001) compared with normotensive subjects with diabetes mellitus. After adjustment for demographic and clinical covariates, hypertension was associated with a 72% increase in the risk of all-cause death and a 57% increase in the risk of any cardiovascular event in individuals with diabetes mellitus. The population-attributable risk from hypertension in individuals with diabetes mellitus was 30% for all-cause death and 25% for any cardiovascular event (increasing to 44% and 41%, respectively, if the 110 normotensive subjects who developed hypertension during follow-up were excluded from the analysis). In comparison, after adjustment for concurrent hypertension, the population-attributable risk from diabetes mellitus in Framingham subjects was 7% for all-cause mortality and 9% for any cardiovascular disease event. Although diabetes mellitus is associated with increased risks of death and cardiovascular events in Framingham subjects, much of this excess risk is attributable to coexistent hypertension.

Measuring agreement of administrative data with chart data using prevalence unadjusted and adjusted kappa.

BackgroundKappa is commonly used when assessing the agreement of conditions with reference standard, but has been criticized for being highly dependent on the prevalence. To overcome this limitation, a prevalence-adjusted and bias-adjusted kappa (PABAK) has been developed. The purpose of this study is to demonstrate the performance of Kappa and PABAK, and assess the agreement between hospital discharge administrative data and chart review data conditions.MethodsThe agreement was compared for random sampling, restricted sampling by conditions, and case-control sampling from the four teaching hospitals in Alberta, Canada from ICD10 administrative data during January 1, 2003 and June 30, 2003. A total of 4,008 hospital discharge records and chart view, linked for personal unique identifier and admission date, for 32 conditions of random sampling were analyzed. The restricted sample for hypertension, myocardial infarction and congestive heart failure, and case-control sample for those three conditions were extracted from random sample. The prevalence, kappa, PABAK, positive agreement, negative agreement for the condition was compared for each of three samples.ResultsThe prevalence of each condition was highly dependent on the sampling method, and this variation in prevalence had a significant effect on both kappa and PABAK. PABAK values were obviously high for certain conditions with low kappa values. The gap between these two statistical values for the same condition narrowed as the prevalence of the condition approached 50%.ConclusionKappa values varied more widely than PABAK values across the 32 conditions. PABAK values should usually not be interpreted as measuring the same agreement as kappa in administrative data, particular for the condition with low prevalence. There is no single statistic measuring agreement that captures the desired information for validity of administrative data. Researchers should report kappa, the prevalence, positive agreement, negative agreement, and the relative frequency in each cell (i.e. a, b, c and d) to enable the reader to judge the validity of administrative data from multiple aspects.

Trends in antihypertensive drug prescriptions and physician visits in Canada between 1996 and 2006

BACKGROUND In 1999, the Canadian Hypertension Education Program (CHEP) was launched to develop and implement evidence-based hypertension guidelines. OBJECTIVES To determine temporal trends in antihypertensive drug prescribing and physician visits for hypertension in Canada, and correlate these trends with CHEP recommendations. METHODS Longitudinal drug data (Intercontinental Medical Statistics [IMS] CompuScript database; IMS Health Canada) were used to examine prescriptions over an 11-year period (1996 to 2006) for five major cardiovascular drug classes. The IMS Canadian Disease and Therapeutic Index database was used to determine trends in physician office visits for hypertension. RESULTS Prescriptions for antihypertensive agents increased significantly over the 11-year period (4054% for angiotensin receptor blockers, 127% for thiazide diuretics, 108% for angiotensin-converting enzyme inhibitors, 87% for beta-blockers and 55% for calcium channel blockers). Time series analyses demonstrated increases in the growth rate for all drug classes, with the greatest annual change in prescriptions occurring during the 1999 to 2002 time period (except in angiotensin receptor blockers). An increase in prescriptions for fixed-dose combination products occurred, which was temporally related to the change in CHEP recommendations encouraging their use in 2001. The proportion of physician office visits for hypertension increased significantly from 4.9% in 1995 to 6.8% in 2005 (P<0.001). CONCLUSIONS The largest increase in antihypertensive drug prescribing occurred in the period immediately following implementation of CHEP (1999 to 2002). Although prescribing rates are still increasing, the rate of change has decreased, suggesting that the treatment market for hypertension may be becoming saturated. The impact of these changes on blood pressure control and clinical outcomes remains to be determined.

Incidence, cardiovascular complications and mortality of hypertension by sex and ethnicity

Objective To compare ethnic and sex difference in the incidence of newly diagnosed hypertension, and subsequent risk of cardiovascular disease outcomes among South Asian, Chinese and white patients. Methods We identified patients with newly diagnosed hypertension aged ≥20 years. Patients were followed for 1–9 years for all-cause mortality and cardiovascular disease with myocardial infarction, heart failure and stroke. Cox proportional hazard models stratified by sex and adjusted for age, median income and co-morbid conditions, were constructed to determine the independent association between ethnicity and the development of the combined cardiovascular endpoint as well as death. Results There were 39 175 South Asian (49.4% men, 34.4% age ≥65), 49 892 Chinese (48.1% men, 36.7% age ≥65) and 841 277 white (47.9% men, 38.8% age ≥65) patients with newly diagnosed hypertension. Age and sex adjusted incidence of hypertension was highest in South Asian patients and lowest in Chinese patients. Compared with white patients, South Asian and Chinese patients had a lower mortality (adjusted HR (aHR) 0.91 and 0.66) and risk of cardiovascular disease outcomes (aHR 0.94 and 0.49). Compared to men, women had significantly lower mortality (aHR: 0.83 for Chinese, 0.78 for South Asian and 0.77 for white) and cardiovascular disease outcomes (0.72 for Chinese, 0.63 for South Asian and 0.65 for white). Conclusions South Asian patients had higher rates of hypertension compared to the other ethnic groups. South Asian and Chinese patients had a lower risk of death and developing cardiovascular outcomes compared to whites. Women with hypertension have a better prognosis than men regardless of ethnicity.

Canadian Provincial Trends in Antihypertensive Drug Prescriptions Between 1996 and 2006

BACKGROUND Little is known regarding potential differences in antihypertensive prescribing practices at a Canadian provincial level. Our objective was to determine provincial differences in the use of antihypertensive drug therapy in Canada. METHODS Using longitudinal drug data (IMS CompuScript database; IMS Health Canada), we examined the increase in number of prescriptions dispensed for all antihypertensive agents for each province over an 11-year period (1996-2006). RESULTS Over the 11-year study period, antihypertensive prescriptions increased by 106.2% for single-drug therapy (from 35.8% in Prince Edward Island and Newfoundland to 167.2% in British Columbia) and by 112.8% (from 22.0% in New Brunswick to 216.0% in Québec) for combination-drug therapy. Among drug classifications, angiotensin receptor blockers had the largest increase for single-drug therapy and angiotensin-converting enzyme inhibitors-diuretics for combination-drug therapy. There were marked provincial differences in the increase in total antihypertensive therapy, ranging from British Columbia, with an increase of 262%, to Prince Edward Island and Newfoundland, where the increase was 134%. CONCLUSION Large increases in antihypertensive prescriptions occurred in all provinces of Canada, but the provinces varied substantially in the increase in total and drug-specific classes of antihypertensive drugs. The basis for provincial differences in antihypertensive prescriptions remains unknown and is likely multifactorial but may relate in part to initial provincial variations in diagnosis, treatment, and control of hypertension, as well as individual provincial drug policies.

Regional variations in not treating diagnosed hypertension in Canada

BACKGROUND Improvements in the diagnosis and treatment of hypertension have been documented in Canada following implementation of a national program to improve hypertension management. OBJECTIVE To determine whether there are regional variations in not treating diagnosed hypertension with drugs in Canada. METHODS Using data from the Canadian Community Health Survey (CCHS) cycle 3.1 (2005), regional variation in drug treatment of diagnosed hypertension was examined. Also, national drug data from the Intercontinental Medical Statistics CompuScript database were analyzed to determine regional trends in total antihypertensive prescriptions in the period before and following the CCHS cycle 3.1. RESULTS The overall rate of untreated hypertension among those diagnosed with hypertension in Canada was 12.7%. The highest untreated rate among those diagnosed with hypertension was in the Northern region (29.2%) and the lowest was in the Atlantic region (8.8%). Alberta (16.5%) and British Columbia (BC) (15.4%) also had higher untreated rates, while Ontario (13.2%) was similar to Canada overall. Younger age, single⁄never married status, larger household size, lack of access to a family physician and daily smoking were all associated with a higher likelihood of not receiving antihypertensive treatment. Adjusting for demographic characteristics, diagnosed hypertensive patients in Alberta (adjusted OR 1.35 [95% CI 1.14 to 1.61]) and BC (adjusted OR 1.64 [95% CI 1.40 to 1.91]) were more likely to be untreated than those in Ontario. The largest overall percentage increase in total antihypertensive prescriptions following the CCHS (ie, 2006) occurred in BC and Ontario. In Alberta, it remained almost unchanged and declined in Manitoba. CONCLUSIONS Among adult Canadians diagnosed with hypertension, there were regional variations in the likelihood of not receiving antihypertensive therapy. Further research is required to understand the reasons for these variations to regionally target interventions and improve hypertension management in Canada.

Meta-Analysis of Adverse Cardiovascular Outcomes Associated With Antecedent Hypertension After Myocardial Infarction

The aim of this study was to investigate the association of antecedent hypertension with adverse cardiovascular outcomes after myocardial infarction. A search of Medline and EMBASE was supplemented by manual searches of the bibliographies of key retrieved reports. The studies were included if they reported antecedent hypertension as a risk factor for adverse outcomes (death, stroke, congestive heart failure, recurrent myocardial infarction) in survivors of myocardial infarctions. Relative risks (RRs) were pooled using a random-effects model, and the robustness of the pooled RRs was evaluated in sensitivity analyses. Cumulative meta-analysis, by chronologic year of study beginning, was also performed. The search yielded 17 studies (n = 56,748 participants) that reported antecedent hypertension with adverse outcomes for survivors of myocardial infarctions. Randomized clinical trials (n = 8) were pooled separately from cohort studies (n = 9). For randomized clinical trials, the pooled RRs were 1.19 (95% confidence interval [CI] 1.13 to 1.26) for all-cause mortality and 1.29 (95% CI 1.09 to 1.53) for cardiovascular disease mortality. For cohort studies, the pooled RRs were 1.46 (95% CI 1.34 to 1.61) for all-cause mortality and 1.54 (95% CI 1.22 to 1.93) for cardiovascular disease mortality. Antecedent hypertension was also consistently associated with an increased risk for stroke, congestive heart failure, and recurrent myocardial infarction. Pooled estimates were robust in sensitivity analysis. In conclusion, antecedent hypertension was associated with adverse outcomes for survivors of myocardial infarctions, the association of antecedent hypertension with all-cause mortality outcomes decreased over time, and this decreased association reflects improved treatment and management of hypertension in more recent years.

Outcomes Among 3.5 Million Newly Diagnosed Hypertensive Canadians

BACKGROUND This population-based study assessed rates of all-cause mortality, myocardial infarction, heart failure, and stroke for up to 12 years of follow-up in 3.5 million Canadian adults newly diagnosed with hypertension. METHODS Hypertension cohort, outcomes, and covariates were defined using validated case definitions applied to inpatient and outpatient administrative health databases. Factors associated with each outcome were identified using Cox proportional hazards models. RESULTS Of 3,531,089 adults newly diagnosed with hypertension and without a previous history of cardiovascular disease, 29.4% were younger than 50 years of age; 48.2% were male, and 17.2% resided in a rural area. Over a median follow-up length of 6.1 years, the crude all-cause mortality rate was 22.4 per 1000 person-years. The incidence of hospitalized myocardial infarction (8.4 per 1000 person-years) and hospitalized heart failure (8.5 per 1000 person-years) was higher than stroke (6.9 per 1000 person-years). The incidence rate for any cardiovascular hospitalization was 19.3 per 1000 person-years. Older age, male sex, lower income, rural residence, and a higher number of Charlson comorbidities were each independently associated with a higher risk of mortality and incident cardiovascular disease hospitalizations. CONCLUSIONS In a nationally-representative incident cohort of hypertensive adults we have demonstrated higher mortality rates and poorer outcomes for the elderly, males, and those living in rural or low income locations. Innovative approaches to the provision of care for these high-risk individuals will lead to improved patient outcomes.