Interrupted time series designs in health technology assessment: lessons from two systematic reviews of behavior change strategies
International journal of technology assessment in health care, 2003•cambridge.org
Objectives: In an interrupted time series (ITS) design, data are collected at multiple instances
over time before and after an intervention to detect whether the intervention has an effect
significantly greater than the underlying secular trend. We critically reviewed the
methodological quality of ITS designs using studies included in two systematic reviews (a
review of mass media interventions and a review of guideline dissemination and
implementation strategies). Methods: Quality criteria were developed, and data were …
over time before and after an intervention to detect whether the intervention has an effect
significantly greater than the underlying secular trend. We critically reviewed the
methodological quality of ITS designs using studies included in two systematic reviews (a
review of mass media interventions and a review of guideline dissemination and
implementation strategies). Methods: Quality criteria were developed, and data were …
Objectives
In an interrupted time series (ITS) design, data are collected at multiple instances over time before and after an intervention to detect whether the intervention has an effect significantly greater than the underlying secular trend. We critically reviewed the methodological quality of ITS designs using studies included in two systematic reviews (a review of mass media interventions and a review of guideline dissemination and implementation strategies).
Methods
Quality criteria were developed, and data were abstracted from each study. If the primary study analyzed the ITS design inappropriately, we reanalyzed the results by using time series regression.
Results
Twenty mass media studies and thirty-eight guideline studies were included. A total of 66% of ITS studies did not rule out the threat that another event could have occurred at the point of intervention. Thirty-three studies were reanalyzed, of which eight had significant preintervention trends. All of the studies were considered “effective” in the original report, but approximately half of the reanalyzed studies showed no statistically significant differences.
Conclusions
We demonstrated that ITS designs are often analyzed inappropriately, underpowered, and poorly reported in implementation research. We have illustrated a framework for appraising ITS designs, and more widespread adoption of this framework would strengthen reviews that use ITS designs.
Cambridge University Press