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Biomedical subjects

Philip Wells

Publications and source records attributed to Philip Wells.

5 recordsLinked to original sources
PubMed2006

The effect of hospitalization on oral anticoagulation control: a population-based study.

BACKGROUND: For patients taking oral anticoagulants (OAC), the proportion of time spent in the therapeutic range is strongly associated with bleeding and thromboembolic risk. Previous studies examining OAC control may not generalize because the patient population was select or INR capture was incomplete. OBJECTIVES: Measure OAC control for an entire population of elderly people and determine patient factors associated with OAC control. PATIENTS: People in Eastern Ontario without valve replacement aged 65 years or greater who were treated with warfarin between 1 September 1999 and 1 September 2000. DESIGN: Retrospective cohort study using population-based administrative databases. OAC control was measured as the proportion of days in therapeutic range (PDTR), defined as the number days with the INR between 2 and 3 divided by total number of days observation. Linear interpolation was used to determine INR levels between measures. Negative binomial regression was used to identify patient factors independently associated with PDTR. We also determined which factors were associated with proportion of days with a critically low (<1.5) or critically high (>/=5) INR. RESULTS: 7179 people were followed for a total of 3238 years. 15% of people were hospitalized during the study. Overall, PDTR was 59.2% (95% CI 59.1%-59.2%). Independent of all other significant factors, hospitalization was associated with a 15% decrease in the PDTR 15% (rate ratio 0.85, 95% CI 0.83-0.87). Hospitalization was also independently associated with greater proportion of time with a critically low INR (rate ratio 1.68, 95% CI 1.51-1.88) and a critically high INR (1.70, 95% CI 1.38-2.08). CONCLUSIONS: Elderly people in eastern Ontario taking warfarin were therapeutic 59.2% of the time. Independent of other patient factors, patients who are hospitalized have the greatest risk of poor anticoagulation control. Control for anticoagulated patients who get hospitalized should be reviewed to determine if and how it could be improved.

Aged↗
PubMed2006

An evaluation of D-dimer in the diagnosis of pulmonary embolism: a randomized trial.

BACKGROUND: It may be safe to omit additional diagnostic testing in selected patients with suspected pulmonary embolism (PE) who have a negative D-dimer test, but this approach has never been evaluated in a randomized, controlled trial. OBJECTIVE: To determine if additional diagnostic testing can be safely withheld in patients with suspected PE who have negative erythrocyte agglutination D-dimer test results. DESIGN: Randomized comparisons in 2 subgroups of a prospective multicenter study. SETTING: 7 university hospitals. PATIENTS: 1126 outpatients or inpatients with suspected PE; of these, 456 patients with negative erythrocyte agglutination D-dimer test results were randomly assigned to the intervention groups. Patients were classified into 2 clinical probability groups: those with a low clinical probability of PE (low-probability group) and those with a moderate or high clinical probability of PE, a nondiagnostic ventilation-perfusion lung scan, and no evidence of proximal deep venous thrombosis on bilateral ultrasonography (moderate- or high-probability group). INTERVENTIONS: The experimental intervention for both probability groups was no further diagnostic testing for PE. The control intervention for the low-probability group was a ventilation-perfusion lung scan followed by ultrasonography of the proximal deep veins of the legs on the same day. If the lung scan was nondiagnostic, ultrasonography of the legs was repeated 7 and 14 days later. The control intervention for the moderate- or high-probability group was ultrasonography of the proximal deep veins of the legs after 7 and 14 days. In the control and experimental groups, anticoagulation was withheld or withdrawn if PE was not diagnosed. MEASUREMENTS: Symptomatic venous thromboembolism (VTE) during 6 months of follow-up. RESULTS: Prevalence of VTE was 15.2% in the 1126 enrolled patients. In the low-probability group, VTE occurred during follow-up in 0 of 182 patients who had no additional diagnostic testing and in 1 of 185 patients who had additional testing (difference, -0.5 percentage point [95% CI, -3.0 to 1.6 percentage points]). In the moderate- or high-probability group, VTE occurred during follow-up in 1 of 41 patients who had no additional diagnostic testing and in 0 of 41 patients who had additional testing (difference, 2.4 percentage points [CI, -6.4 to 12.6 percentage points]). LIMITATIONS: The authors could not enroll 2000 patients as originally planned; 3 randomly assigned patients did not receive the allocated intervention, and 7 received inadequate follow-up. Personnel who performed follow-up evaluations were not blinded to the results of diagnostic testing at enrollment or to allocation group assignments. CONCLUSION: In patients with a low probability of PE who have negative D-dimer results, additional diagnostic testing can be withheld without increasing the frequency of VTE during follow-up. Low clinical probability and negative D-dimer results occur in 50% of outpatients and in 20% of inpatients with suspected PE.

Fibrin Fibrinogen Degradation Products↗
PubMed2004

Analytical validation of the tag-it high-throughput microsphere-based universal array genotyping platform: application to the multiplex detection of a panel of thrombophilia-associated single-nucleotide polymorphisms.

BACKGROUND: We have developed a novel, microsphere-based universal array platform referred to as the Tag-It platform. This platform is suitable for high-throughput clinical genotyping applications and was used for multiplex analysis of a panel of thrombophilia-associated single-nucleotide polymorphisms (SNPs). METHODS: Genomic DNA from 132 patients was amplified by multiplex PCR using 6 primer sets, followed by multiplex allele-specific primer extension using 12 universally tagged genotyping primers. The products were then sorted on the Tag-It array and detected by use of the Luminex xMAP system. Genotypes were also determined by sequencing. RESULTS: Empirical validation of the universal array showed that the highest nonspecific signal was 3.7% of the specific signal. Patient genotypes showed 100% concordance with direct DNA sequencing data for 736 SNP determinations. CONCLUSIONS: The Tag-It microsphere-based universal array platform is a highly accurate, multiplexed, high-throughput SNP-detection platform.

Genotype↗
PubMed2003

Comparison of low-intensity warfarin therapy with conventional-intensity warfarin therapy for long-term prevention of recurrent venous thromboembolism.

BACKGROUND: Warfarin is very effective in preventing recurrent venous thromboembolism but is also associated with a substantial risk of bleeding. After three months of conventional warfarin therapy, a lower dose of anticoagulant medication may result in less bleeding and still prevent recurrent venous thromboembolism. METHODS: We conducted a randomized, double-blind study, in which 738 patients who had completed three or more months of warfarin therapy for unprovoked venous thromboembolism were randomly assigned to continue warfarin therapy with a target international normalized ratio (INR) of 2.0 to 3.0 (conventional intensity) or a target INR of 1.5 to 1.9 (low intensity). Patients were followed for an average of 2.4 years. RESULTS: Of 369 patients assigned to low-intensity therapy, 16 had recurrent venous thromboembolism (1.9 per 100 person-years), as compared with 6 of 369 assigned to conventional-intensity therapy (0.7 per 100 person-years; hazard ratio, 2.8; 95 percent confidence interval, 1.1 to 7.0). A major bleeding episode occurred in nine patients assigned to low-intensity therapy (1.1 events per 100 person-years) and eight patients assigned to conventional-intensity therapy (0.9 event per 100 person-years; hazard ratio, 1.2; 95 percent confidence interval, 0.4 to 3.0). There was no significant difference in the frequency of overall bleeding between the two groups (hazard ratio, 1.3; 95 percent confidence interval, 0.8 to 2.1). CONCLUSIONS: Conventional-intensity warfarin therapy is more effective than low-intensity warfarin therapy for the long-term prevention of recurrent venous thromboembolism. The low-intensity warfarin regimen does not reduce the risk of clinically important bleeding.

Age Factors↗