Patient Registries of Acute Coronary Syndrome Assessing or Biasing the Clinical Real World Data?
ABSTRACT The risk of selection bias in registries and its consequences are relatively unexplored. We sought to assess selection bias in a recent registry about acute coronary syndrome and to explore the way of conducting and reporting patient registries of acute coronary syndrome.
We analyzed data from patients of a national acute coronary syndrome registry undergoing an audit about the comprehensiveness of the recruitment/inclusion. Patients initially included by hospital investigators (n=3265) were compared to eligible nonincluded (missed) patients (n=1439). We assessed, for 25 exposure variables, the deviation of the in-hospital mortality relative risks calculated in the initial sample from the actual relative risks. Missed patients were of higher risk and received less recommended therapies than the included patients. In-hospital mortality was almost 3 times higher in the missed population (9.34% [95% CI, 7.84 to 10.85] versus 3.9% [95% CI, 2.89 to 4.92]). Initial relative risks diverged from the actual relative risks more than expected by chance (P<0.05) in 21 variables, being higher than 10% in 17 variables. This deviation persisted on a smaller degree on multivariable analysis. Additionally, we reviewed a sample of 129 patient registries focused on acute coronary syndrome published in thirteen journals, collecting information on good registry performance items. Only in 38 (29.4%) and 48 (37.2%) registries was any audit of recruitment/inclusion and data abstraction, respectively, mentioned. Only 4 (3.1%) authors acknowledged potential selection bias because of incomplete recruitment.
Irregular inclusion can introduce substantial systematic bias in registries. This problem has not been explicitly addressed in a substantial number of them.
Full-textDOI: · Available from: Héctor Bueno, Feb 28, 2014
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ABSTRACT: A switched stiffness semi-active vibration attenuation method implemented with a simple relay-type control logic for flexible mechanical structures is presented. A single degree of freedom system is considered for validation of the switched stiffness concept. The method is then applied to a flexible beam with moving base, representing the last link of a Cartesian-type robot manipulator. A piezoelectric actuator, attached on the top surface of the flexible beam, is switched between open and short circuit configurations. This switching introduces a change in stiffness, which, in turn, can remove energy from the overall system by directly affecting the stored potential energy in the flexible beam. The control logic for switching stiffness is based on the position and velocity feedback of the tip of the flexible beam. Implementation of this control logic is hindered by the lack of velocity sensors. A numerical differentiator may be utilized, but may degrade the vibration suppression performance due to the phase lag introduced by filters utilized for conditioning the resultant noisy signal. In order to remedy this, a novel output feedback variable structure velocity observer scheme applicable for a general nonlinear mechanical system with unknown system dynamics is utilized. Simulation results show superior vibration attenuation for both the single degree of freedom oscillator and the cantilever flexible beam systems with velocity observer.American Control Conference, 2004. Proceedings of the 2004; 01/2004
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