Examining the Internal Validity and Statistical Precision of the Comparative Interrupted Time Series Design by Comparison With a Randomized Experiment

Clair, Travis St.; Cook, Thomas D.; Hallberg, Kelly

doi:10.1177/1098214014527337

Cited by 79 publications

(68 citation statements)

References 22 publications

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“…Controlled interrupted time series designs are among the most robust for causal inference, and accumulating evidence suggests that matching on baseline trend generates effect estimates similar to randomized clinical trials. 38 …”

Section: Discussionmentioning

confidence: 99%

Comparing Medical Costs and Use After Laparoscopic Adjustable Gastric Banding and Roux-en-Y Gastric Bypass

et al. 2015

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IMPORTANCE There is conflicting evidence about how different bariatric procedures impact health care use. OBJECTIVE To compare the impact of laparoscopic adjustable gastric banding (AGB) and laparoscopic Roux-en-Y gastric bypass (RYGB) on health care use and costs. DESIGN, SETTING, AND PARTICIPANTS Retrospective interrupted time series with comparison series study using a national claims data set. The data analysis was initiated in September 2011 and completed in January 2015. We identified bariatric surgery patients aged 18 to 64 years who underwent a first AGB or RYGB between 2005 and 2011. We propensity score matched 4935 AGB to 4935 RYGB patients according to baseline age group, sex, race/ethnicity, socioeconomic variables, comorbidities, year of procedure and baseline costs, emergency department (ED) visits, and hospital days. Median postoperative follow-up time was 2.5 years. MAIN OUTCOMES AND MEASURES Quarterly and yearly total health care costs, ED visits, hospital days, and prescription drug costs. We used segmented regression to compare pre-to-post changes in level and trend of these measures in the AGB vs the RYGB groups and difference-in-differences analysis to estimate the magnitude of difference by year. RESULTS Both AGB and RYGB were associated with downward trends in costs; however, by year 3, AGB patients had total annual costs that were 16% higher than RYGB patients (P < .001; absolute change: $818; 95% CI, $278 to $1357). In postoperative years 1 and 2, AGB was associated with 27% to 29% fewer ED visits than RYGB (P < .001; absolute changes: −0.6; 95% CI, −0.9 to −0.4 and −0.4; 95% CI, −0.6 to −0.1 visits/person, respectively); however, by year 3, there were no detectable differences. Postoperative annual hospital days were not significantly different between the groups. Although both procedures lowered prescription costs, annual postoperative prescription costs were 17% to 32% higher for AGB patients than RYGB patients (P < .001). CONCLUSIONS AND RELEVANCE Both laparoscopic AGB and RYGB were associated with flattened total health care cost trajectories but RYGB patients experienced lower total and prescription costs by 3 years postsurgery. On the other hand, RYGB was associated with increased ED visits in the 2 years after surgery. Clinicians and policymakers should weigh such differences in use and costs when making recommendations or shaping regulatory guidance about these procedures.

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Section: Discussionmentioning

confidence: 99%

Comparing Medical Costs and Use After Laparoscopic Adjustable Gastric Banding and Roux-en-Y Gastric Bypass

et al. 2015

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“…We also matched on baseline quarterly numbers of high-priority (defined below) primary care and specialist visits, preventable acute diabetes complication visits (defined below), ED visits, hospitalization days, and baseline quarterly total out-of-pocket spending per member. 8,9 Compared with the unmatched sample, our propensity score matching approach increased the similarity of the HDHP and control groups with respect to age, gender, neighborhood poverty level, morbidity score, baseline outpatient copayment, and employer size (Table 1). Our final group included 12,084 HDHP members with diabetes and their 1:1 matched controls.…”

Section: Methodsmentioning

confidence: 99%

Diabetes Outpatient Care and Acute Complications Before and After High-Deductible Insurance Enrollment

et al. 2017

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High-deductible health plans (HDHPs) have expanded under the Affordable Care Act and are expected to play a major role in the future of US health policy. The effects of modern HDHPs on chronically ill patients and adverse outcomes are unknown.OBJECTIVE To determine the association of HDHP with high-priority diabetes outpatient care and preventable acute complications.DESIGN, SETTING, AND PARTICIPANTS Controlled interrupted-time-series study using a large national health insurer database from January 1, 2003, to December 31, 2012. A total of 12 084 HDHP members with diabetes, aged 12 to 64 years, who were enrolled for 1 year in a low-deductible (Յ$500) plan followed by 2 years in an HDHP (Ն$1000) after an employer-mandated switch were included. Patients transitioning to HDHPs were propensity-score matched with contemporaneous patients whose employers offered only low-deductible coverage. Low-income (n = 4121) and health savings account (HSA)-eligible (n = 1899) patients with diabetes were subgroups of interest. Data analysis was performed from February 23, 2015, to September 11, 2016.EXPOSURES Employer-mandated HDHP transition.MAIN OUTCOMES AND MEASURES High-priority outpatient visits, disease monitoring tests, and outpatient and emergency department visits for preventable acute diabetes complications. RESULTSIn the 12 084 HDHP members included after the propensity score match, the mean (SD) age was 50.4 (10.0) years; 5410 of the group (44.8%) were women. The overall, low-income, and HSA-eligible diabetes HDHP groups experienced increases in out-of-pocket medical expenditures of 49.4% (95% CI, 40.3% to 58.4%), 51.7% (95% CI, 38.6% to 64.7%), and 67.8% (95% CI, 47.9% to 87.8%), respectively, compared with controls in the year after transitioning to HDHPs. High-priority primary care visits and disease monitoring tests did not change significantly in the overall HDHP cohort; however, high-priority specialist visits declined by 5.5% (95% CI, −9.6% to −1.5%) in follow-up year 1 and 7.1% (95% CI, −11.5% to −2.7%) in follow-up year 2 vs baseline. Outpatient acute diabetes complication visits were delayed in the overall and low-income HDHP cohorts at follow-up (adjusted hazard ratios, 0.94 [95% CI, 0.88 to 0.99] for the overall cohort and 0.89 [95% CI, 0.81 to 0.98] for the low-income cohort). Annual emergency department acute complication visits among HDHP members increased by 8.0% (95% CI, 4.6% to 11.4%) in the overall group, 21.7% (95% CI, 14.5% to 28.9%) in the low-income group, and 15.5% (95% CI, 10.5% to 20.6%) in the HSA-eligible group.CONCLUSIONS AND RELEVANCE Patients with diabetes experienced minimal changes in outpatient visits and disease monitoring after an HDHP switch, but low-income and HSA-eligible HDHP members experienced major increases in emergency department visits for preventable acute diabetes complications.

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“…The second method is comparative/controlled interrupted time series (CITS). The method has been proved to be valid and precise, and is considered more flexible than DD, rendering it superior under certain conditions. More specifically, while the DD method assumes that outcome trends are similar, that is, “common,” between the intervention and the non‐intervention groups, the CITS method relaxes the assumption and allows those trends to diverge .…”

Section: Methodsmentioning

confidence: 99%

Effectiveness of antimalarial interventions in Nigeria: Evidence from facility‐level longitudinal data

Witvorapong

Yakubu²

2019

Health Services Research

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Objective To evaluate the effectiveness of a program of antimalarial interventions implemented in 2010‐2013 in Niger State, Nigeria. Data Sources Utilization reports from 99 intervention and 51 non‐intervention health facilities from the Niger State Malaria Elimination Program, supplemented by data on facility‐level characteristics from the Niger State Primary Health Care Development Agency and Local Government Malaria Control units. Study Design Estimated with mixed‐effects negative binomial modeling, a difference‐in‐differences method was used to quantify the impact of the program on the number of febrile illness cases and confirmed malaria cases. Potential confounding factors, non‐stationarity, seasonality, and autocorrelation were explicitly accounted for. Data Extraction Methods Data were retrieved from hard copies of utilization reports and manually inputted to create a panel of 5550 facility‐month observations. Principal Findings The program was implemented in two phases. The first phase (August 2010‐June 2012) involved the provision of free artemisinin‐based combination therapies, long‐lasting insecticidal nets, and intermittent preventive treatments. In the second phase (July 2012‐March 2013), the program introduced an additional intervention: free parasite‐based rapid diagnostic tests. Compared to the pre‐intervention period, the average number of monthly febrile illness and malaria cases increased by 20.876 (P < 0.01) and 22.835 (P < 0.01) in the first phase, and by 19.007 (P < 0.05) and 19.681 (P < 0.05) in the second phase, respectively. The results are consistent across different evaluation methods. Conclusions This study suggests that user‐fee removal leads to increased utilization of antimalarial services. It motivates future studies to cautiously select their investigative methods.

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Examining the Internal Validity and Statistical Precision of the Comparative Interrupted Time Series Design by Comparison With a Randomized Experiment

Cited by 79 publications

References 22 publications

Comparing Medical Costs and Use After Laparoscopic Adjustable Gastric Banding and Roux-en-Y Gastric Bypass

Comparing Medical Costs and Use After Laparoscopic Adjustable Gastric Banding and Roux-en-Y Gastric Bypass

Diabetes Outpatient Care and Acute Complications Before and After High-Deductible Insurance Enrollment

Effectiveness of antimalarial interventions in Nigeria: Evidence from facility‐level longitudinal data

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