Abstract
Background
Immortal time bias is a possible confounding factor in cohort studies. In this investigation,
we assessed mortality with inferior vena cava (IVC) filters in unstable patients with
pulmonary embolism using a design to control for immortal time bias.
Methods
Data were from the Premier Healthcare Database, 2010-2014. International Classification
of Diseases-Ninth Revision-Clinical Modification codes were used. Unstable patients
with pulmonary embolism and an admitting diagnosis of pulmonary embolism, as well
as a primary diagnosis of pulmonary embolism, were included. A time-dependent analysis
was used according to the day of insertion of the IVC filter to control for immortal
time bias.
Results
Among all unstable patients, irrespective of the use of thrombolytic therapy, in-hospital
all-cause mortality was 35 of 180 (19.4%) in those who received an IVC filter vs 122
of 299 (40.8%) with no filter (P < .0001). Mortality was lower in patients in whom the IVC filter was inserted on
days 1 or 2 (on day 1, 21.4% compared with 40.8%, P = .017, and on day 2, 14.8% compared with 29.2%, P = .023), but it was not lower in those in whom the filter was inserted on subsequent
days.
Conclusions
Mortality in unstable patients with pulmonary embolism appeared to be reduced with
IVC filters only when the filter was inserted on the first or second day of admission.
The design used for these analyses controlled for immortal time bias as a cause of
the lower mortality with IVC filters.
Keywords
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Article info
Publication history
Published online: June 12, 2018
Footnotes
Funding: None.
Conflict of Interest: None.
Authorship: All authors had access to the data and a role in writing this manuscript.
Identification
Copyright
© 2018 Elsevier Inc. All rights reserved.
