INR control calculation: comparison of Dutch and international methods.

Results of trials with new oral anticoagulant drugs and vitamin K antagonists (VKA) might not be directly applicable to Dutch clinical practice due to the high level of control of anticoagulation in the Netherlands. In addition, the Dutch method for assessing anticoagulation control uses cross-sectional international normalised ratio (INR) test results while the method used in the trials is based on person-time. To enable comparisons, the two calculation methods were applied to INR data of a cohort of 5422 atrial fibrillation patients treated with VKA. Overall, 74% of test results and 77% of person-time were in the therapeutic range [2.0-3.5]. For the narrower target INR interval [2.5-3.5], 59% of test results and 61% of person-time were in range. It was only between two and six months after the start of treatment that the percentage of person-time in range was lower than the percentage of test results in range. Control of anticoagulation, expressed as a percentage of person-time spent in range, in this Dutch dataset was similar to recent trials with new oral anticoagulants, although it should be noted that the Dutch INR target is higher than the target in these trials. INR control as estimated by the two calculation methods (cross-sectional and longitudinal) was similar.

Daily mortality and air pollution along busy streets in Amsterdam, 1987-1998.

Time-series studies on the association between daily mortality and air pollution levels have been criticized because they use background air pollution measurement sites to estimate exposure of the whole population, including those living along busy roads. To evaluate whether the exposure of people living along busy roads is estimated with error, we calculated separate effect estimates with separate exposure estimates using background and traffic-influenced measurement stations. We used Poisson regression analysis with generalized additive models to correct for long-term trends, influenza, ambient temperature and relative humidity, and day of the week. Black smoke and nitrogen dioxide were associated with mortality (relative risk of 1.38 and 1.10, respectively, for an increase of 100 microg/m3 on the previous day). Effect estimates were larger in the summer and in the population living along busy roads. Effect estimates were also larger using background stations rather than traffic stations. Overall, we found differences in the association between mortality and air pollution using different methods of exposure assessment; these differences are attributable to exposure misclassification for populations living along busy roads.

Differences among black smoke, PM(10), and PM(1.0) levels at Urban Measurement Sites.

n Amsterdam, the Netherlands, we measured airborne particulate matter (PM) during winter 1998-1999, taking daily average measurements at an urban background site, at a busy street, and at a motorway. Comparison of black smoke, PM(10), and PM(1.0) levels showed that daily averages were highly correlated over time. Median daily concentrations were elevated at sites affected by traffic. The highest increase relative to the background in median daily concentration was noted for black smoke at the motorway (300%), whereas for PM(10) and PM(1.0) the increase was only 37% and 30%. These results indicate that mass measurements of ambient particulate matter underestimate the exposure to particles generated by traffic.