Quality of warfarin management in primary care: Determining the stability of international normalized ratios using a nationally representative prospective cohort.

OBJECTIVE: To determine the stability of warfarin anticoagulation using a nationally representative sample of Canadian primary care patients and providers. DESIGN: Prospective cohort study. SETTING: Primary care practices associated with the Canadian Primary Care Sentinel Surveillance Network. PARTICIPANTS: Adult warfarin users with 7 or more evaluable international normalized ratio (INR) readings. MAIN OUTCOMES MEASURES: International normalized ratio time in therapeutic range (TTR) determined using the Rosendaal method; TTR above 75% was considered good INR control and TTR below 60% was considered poor INR control. The primary outcome was the proportion of all warfarin users (using an INR target range of 2.0 to 3.5) with good INR control during their first year taking warfarin who have poor INR control the following year. Secondary outcomes included the TTR using an INR target of 2.0 to 3.0 when restricted to patients with known atrial fibrillation (AF) or venous thromboembolism (VTE); and the proportion of INR values below the target of 2.0 and above the targets of 3.0 and 3.5 in the year before the availability of other oral anticoagulants. RESULTS: Among 18 303 adult warfarin users (mean age of 71.0 years, 46.6% female), the median TTR (INR target range of 2.0 to 3.5) was 77.4% (interquartile range of 64.6% to 86.4%). The TTR was above 75% in 56.0% of patients and below 60% in 19.3% of patients. Of those exhibiting good INR control in year 1 of anticoagulation therapy, only 10.2% had poor control the following year. When restricted to patients with known AF or VTE (89.7% with AF and 13.5% with VTE), and assuming an INR target range of 2.0 to 3.0, the TTR was 67.8% (interquartile range of 54.8% to 77.9%). Of these patients, 27.9% had INR values below 2.0, and 19.4% and 8.6% had values above 3.0 and 3.5, respectively. CONCLUSION: Primary care warfarin management produces a TTR comparable to that in randomized trials, with out-of-range INR values 3 times more likely to predispose to thrombosis (INR of < 2.0) than to hemorrhage (INR of > 3.5). A history of good INR control does predict future INR stability and meaningfully informs decisions to switch established warfarin users onto newer agents.

From patient care to research: a validation study examining the factors contributing to data quality in a primary care electronic medical record database.

BACKGROUND: Electronic Medical Records (EMRs) are increasingly used in the provision of primary care and have been compiled into databases which can be utilized for surveillance, research and informing practice. The primary purpose of these records is for the provision of individual patient care; validation and examination of underlying limitations is crucial for use for research and data quality improvement. This study examines and describes the validity of chronic disease case definition algorithms and factors affecting data quality in a primary care EMR database. METHODS: A retrospective chart audit of an age stratified random sample was used to validate and examine diagnostic algorithms applied to EMR data from the Manitoba Primary Care Research Network (MaPCReN), part of the Canadian Primary Care Sentinel Surveillance Network (CPCSSN). The presence of diabetes, hypertension, depression, osteoarthritis and chronic obstructive pulmonary disease (COPD) was determined by review of the medical record and compared to algorithm identified cases to identify discrepancies and describe the underlying contributing factors. RESULTS: The algorithm for diabetes had high sensitivity, specificity and positive predictive value (PPV) with all scores being over 90%. Specificities of the algorithms were greater than 90% for all conditions except for hypertension at 79.2%. The largest deficits in algorithm performance included poor PPV for COPD at 36.7% and limited sensitivity for COPD, depression and osteoarthritis at 72.0%, 73.3% and 63.2% respectively. Main sources of discrepancy included missing coding, alternative coding, inappropriate diagnosis detection based on medications used for alternate indications, inappropriate exclusion due to comorbidity and loss of data. CONCLUSIONS: Comparison to medical chart review shows that at MaPCReN the CPCSSN case finding algorithms are valid with a few limitations. This study provides the basis for the validated data to be utilized for research and informs users of its limitations. Analysis of underlying discrepancies provides the ability to improve algorithm performance and facilitate improved data quality.