Calendar time as an instrumental variable in assessing the risk of heart failure with antihyperglycemic drugs

Low-Dose Prasugrel vs. Standard-Dose Clopidogrel for Patients Undergoing Percutaneous Coronary Intervention

BACKGROUND

Low-dose prasugrel (3.75 mg) is used as maintenance therapy for percutaneous coronary intervention; however, data on long-term outcomes are scarce.

METHODS AND RESULTS

We analyzed 5,392 participants in the KiCS-PCI registry who were administered low-dose prasugrel or clopidogrel at discharge between 2008 and 2018 and for whom 2-year follow-up data were available. We adjusted for confounders using matching weight analyses and multiple imputations. Similarly, we used inverse probability- and propensity score-weighted analyses. We also performed instrumental variable analyses. The primary outcomes were acute coronary syndrome (ACS) and bleeding requiring readmission. Secondary outcomes were all-cause death and a composite outcome of ACS, bleeding, heart failure, stroke, coronary bypass requiring admission, and all-cause death. In this cohort, 12.2% of patients were discharged with low-dose prasugrel. Compared with clopidogrel, low-dose prasugrel was associated with a reduced risk of ACS (hazard ratio [HR] 0.58; 95% confidence interval [CI] 0.39-0.85), bleeding (HR 0.62; 95% CI 0.40-0.97), and the composite outcome (HR 0.71; 95% CI 0.59-0.86). Inverse probability-weighted analysis yielded similar results; however, matching weight analysis without multiple imputations and propensity score-matched analyses showed similar outcomes in both groups. Instrumental variable analyses showed reduced risks of ACS and composite outcome for those on low-dose prasugrel. All-cause mortality did not differ in all analyses.

CONCLUSIONS

Low-dose prasugrel demonstrates comparable outcomes to clopidogrel in terms of ACS and bleeding.

Association of Remote Patient Monitoring with Mortality and Healthcare Utilization in Hypertensive Patients: a Medicare Claims-Based Study

BACKGROUND

Hypertension management is complex in older adults. Recent advances in remote patient monitoring (RPM) have warranted evaluation of RPM use and patient outcomes.

OBJECTIVE

To study associations of RPM use with mortality and healthcare utilization measures of hospitalizations, emergency department (ED) utilization, and outpatient visits.

DESIGN

A retrospective cohort study.

PATIENTS

Medicare beneficiaries aged ≥65 years with an outpatient hypertension diagnosis between July 2018 and September 2020. The first date of RPM use with a corresponding hypertension diagnosis was recorded (index date). RPM non-users were documented from those with an outpatient hypertension diagnosis; a random visit was selected as the index date. Six months prior continuous enrollment was required.

MAIN MEASURES

Outcomes studied within 180 days of index date included (i) all-cause mortality, (ii) any hospitalization, (iii) cardiovascular-related hospitalization, (iv) non-cardiovascular-related hospitalization, (v) any ED, (vi) cardiovascular-related ED, (vii) non-cardiovascular-related ED, (viii) any outpatient, (ix) cardiovascular-related outpatient, and (x) non-cardiovascular-related outpatient. Patient demographics and clinical variables were collected from baseline and index date. Propensity score matching (1:4) and Cox regression were performed. Hazard ratios (HR) and 95% confidence intervals (CI) are reported.

KEY RESULTS

The matched sample had 16,339 and 63,333 users and non-users, respectively. Cumulative incidences of mortality outcome were 2.9% (RPM) and 4.3% (non-RPM), with a HR (95% CI) of 0.66 (0.60-0.74). RPM users had lower hazards of any [0.78 (0.75-0.82)], cardiovascular-related [0.79 (0.73-0.87)], and non-cardiovascular-related [0.79 (0.75-0.83)] hospitalizations. No significant association was observed between RPM use and the three ED measures. RPM users had higher hazards of any [1.10 (1.08-1.11)] and cardiovascular-related outpatient visits [2.17 (2.13-2.19)], while a slightly lower hazard of non-cardiovascular-related outpatient visits [0.94 (0.93-0.96)].

CONCLUSIONS

RPM use was associated with substantial reductions in hazards of mortality and hospitalization outcomes with an increase in cardiovascular-related outpatient visits.

Optimal P2Y12 inhibitor durations in older men and older women following an acute myocardial infarction: A nationwide cohort study using Medicare data

Study objective

Identify optimal P2Y12 inhibitor durations balancing ischemic-benefit and bleeding-risk outcomes after acute myocardial infarction (AMI) in older men and women.

Design

Observational retrospective cohort with 2 years of follow-up, using clone-censor-weight marginal structural models to emulate randomization.

Setting

20 % sample of US Medicare administrative claims data.

Participants

P2Y12 inhibitor new users ≥66 years old following 2008-2013 AMI hospitalization.

Exposures

12- to 24-month P2Y12 inhibitor durations in 1-month intervals.

Main outcome measures

Effectiveness outcome (composite of all-cause mortality, recurrent AMI, ischemic stroke), safety outcome (hospitalized bleed), and negative control outcome (heart failure hospitalization).

Results

Of 28,488 P2Y12 inhibitor new users, 51 % were female, 50 % were > 75 years old, 88 % were White/non-Hispanic, and 93 % initiated clopidogrel. Negative control outcome results for 16- through 24-month durations appeared most likely to meet assumptions of no unmeasured confounding. Compared to men taking 24-month therapy, men taking 16-month therapy had higher 2-year risks of the composite effectiveness outcome (relative risk [RR] = 1.08; 95 % confidence interval [95%CI]:1.00-1.15) with similar bleeding risks (RR = 0.98; 95%CI:0.85-1.13). Compared to women taking 24-month therapy, women taking 16-month therapy had similar 2-year risks of the composite effectiveness outcome (RR = 0.98; 95%CI:0.92-1.04) and lower bleeding risks (RR = 0.88; 95%CI:0.80-0.96).

Conclusions

Older men taking 24-month P2Y12 inhibitor therapy had the lowest composite effectiveness outcome risk with no increased bleeding risk compared to shorter durations. Women taking 16-month versus 24-month P2Y12 inhibitor therapy had similar composite effectiveness outcome risks but a substantially lower hospitalized bleeding risk, suggesting durations beyond 15-17 months lacked benefit while increasing bleeding risk.

Conducting Real-world Evidence Studies on the Clinical Outcomes of Diabetes Treatments

Real-world evidence (RWE), the understanding of treatment effectiveness in clinical practice generated from longitudinal patient-level data from the routine operation of the healthcare system, is thought to complement evidence on the efficacy of medications from randomized controlled trials (RCTs). RWE studies follow a structured approach. (1) A design layer decides on the study design, which is driven by the study question and refined by a medically informed target population, patient-informed outcomes, and biologically informed effect windows. Imagining the randomized trial we would ideally perform before designing an RWE study in its likeness reduces bias; the new-user active comparator cohort design has proven useful in many RWE studies of diabetes treatments. (2) A measurement layer transforms the longitudinal patient-level data stream into variables that identify the study population, the pre-exposure patient characteristics, the treatment, and the treatment-emergent outcomes. Working with secondary data increases the measurement complexity compared to primary data collection that we find in most RCTs. (3) An analysis layer focuses on the causal treatment effect estimation. Propensity score analyses have gained in popularity to minimize confounding in healthcare database analyses. Well-understood investigator errors, like immortal time bias, adjustment for causal intermediates, or reverse causation, should be avoided. To increase reproducibility of RWE findings, studies require full implementation transparency. This article integrates state-of-the-art knowledge on how to conduct and review RWE studies on diabetes treatments to maximize study validity and ultimately increased confidence in RWE-based decision making.

Inference without randomization or ignorability: A stability-controlled quasi-experiment on the prevention of tuberculosis

The stability-controlled quasi-experiment (SCQE) is an approach to study the effects of nonrandomized, newly adopted treatments. While covariate adjustment techniques rely on a "no unobserved confounding" assumption, SCQE imposes an assumption on the change in the average nontreatment outcome between successive cohorts (the "baseline trend"). We provide inferential tools for SCQE and its first application, examining whether isoniazid preventive therapy (IPT) reduced tuberculosis (TB) incidence among 26 715 HIV patients in Tanzania. After IPT became available, 16% of untreated patients developed TB within a year, compared with only 0.5% of patients under treatment. Thus, a simple difference in means suggests a 15.5 percentage point (pp) lower risk (p ≪ .001). Adjusting for covariates using numerous techniques leaves this effectively unchanged. Yet, due to confounding biases, such estimates can be misleading regardless of their statistical strength. By contrast, SCQE reveals valid causal effect estimates for any chosen assumption on the baseline trend. For example, assuming a baseline trend near 0 (no change in TB incidence over time, absent this treatment) implies a small and insignificant effect. To argue IPT was beneficial requires arguing that the nontreatment incidence would have risen by at least 0.7 pp per year, which is plausible but far from certain. SCQE may produce narrow estimates when the plausible range of baseline trends can be sufficiently constrained, while in every case it tells us what baseline trends must be believed in order to sustain a given conclusion, protecting against inferences that rely upon infeasible assumptions.

Decreased Antihyperglycemic Drug Use Driven by High Out-of-Pocket Costs Despite Medicare Coverage Gap Closure

OBJECTIVE

Using the 2016 Medicare Part D coverage gap as an example, we explored effects of increased out-of-pocket costs on adherence to branded dipeptidyl peptidase 4 inhibitors (DPP-4i) in patients without financial subsidies relative to subsidized patients who do not experience increased spending during the gap. We also explored seasonality of reinitiation, because discontinuers may be more likely to reinitiate in January when benefits reset.

RESEARCH DESIGN AND METHODS

We identified DPP-4i or sulfonylurea initiators, aged ≥66 years, from a 20% sample of 2015-2016 Medicare claims. Difference-in-differences Poisson regression was used to compare adherence before and after entering the coverage gap between nonsubsidized and subsidized patients. Among discontinuers, monthly hazard ratios (HRs) for reinitiation relative to January 2016 were derived with Cox models. As a second control, we repeated analyses using sulfonylureas, generic low-cost alternatives.

RESULTS

In 2016, 8,096 subsidized and 6,173 nonsubsidized DPP-4i initiators entered the coverage gap. For nonsubsidized patients, copayment in the coverage gap was 45% ($227 per DPP-4i prescription), and adherence decreased from 68.4% to 49.0% after gap entry. Accounting for adherence differences in subsidized patients, nonsubsidized patients demonstrated reduced adherence to DPP-4i (difference-in-difference: -16.9%; 95% CI -18.7%, -15.1%) but not sulfonylureas (-1.6%; 95% CI -3.4%, 0.2%). Reinitiation was lowest in the months before January (HR 0.4-0.5) among nonsubsidized DPP-4i patients, demonstrating a strong seasonal pattern.

CONCLUSIONS

Increased out-of-pocket costs negatively affect adherence and reinitiation of branded antihyperglycemic drugs among patients without financial subsidies. Despite closure of the coverage gap, affordability remains a concern given increasing list prices for many drugs on Medicare and the growing use of deductibles and coinsurance by commercial health plans.

Impact of metformin use on the cardiovascular effects of dipeptidyl peptidase-4 inhibitors: An analysis of Medicare claims data from 2007 to 2015

AIMS

To examine the outcomes of dipeptidyl peptidase-4 (DPP-4) inhibitor initiation with and without concurrent metformin treatment.

MATERIALS AND METHODS

We identified Medicare enrollees initiating a DPP-4 inhibitor, a sulphonylurea or a thiazolidinedione. Using propensity-score-weighted Poisson models, we evaluated 1-year cardiovascular (CV) outcome incidence among initiators of DPP-4 inhibitors versus comparators in subgroups with and without concurrent metformin use, and assessed the interaction between initiation drug and metformin. Outcomes included mortality, non-fatal myocardial infarction (MI), stroke, and a composite outcome.

RESULTS

For the DPP-4 inhibitor (n = 13 391) versus sulphonylurea (n = 33 206) comparison, rate differences in composite outcome incidence favoured DPP-4 inhibitors: -2.0/100 person-years among metformin users (95% confidence interval [CI] -2.7 to -1.3) and - 1.0/100 person-years (95% CI -1.8 to -0.2) among metformin non-users. Similar rate difference trends among metformin users and non-users were seen for mortality (-1.5/100 person-years [95% CI -2.1 to -0.9] and -0.7/100 person-years [95% CI -1.4 to 0.0]) and non-fatal MI (-0.5/100 person-years [95% CI -0.8, -0.3] and 0.1/100 person-years [95% CI -0.2 to 0.4]). The interaction between DPP-4 inhibitor initiation and metformin was statistically significant for non-fatal MI (P = 0.008). For the DPP-4 inhibitor (n = 22 210) versus thiazolidinedione (n = 9517) comparison, rate differences in composite outcome incidence for DPP-4 inhibitor initiation were -0.6/100 person-years (95% CI -1.5 to 0.2) among metformin users and 1.0 (95% CI 0.0 to 2.0) among metformin non-users. Similar rate difference trends among metformin users and non-users were seen for mortality (-0.5/100 person-years [95% CI -1.3 to 0.1] and 0.8/100 person-years [95% CI -0.0 to 1.7]) and non-fatal MI (-0.1/100 person-years [95% CI -0.4 to 0.2] and 0.2/100 person-years [95% CI -0.1 to 0.6]). The interaction between DPP-4 inhibitor initiation and metformin was statistically significant for the composite outcome (P = 0.024) and mortality (P = 0.023).

CONCLUSION

Incidence rate differences in multiple CV outcomes appeared more favourable when DPP-4 inhibitor initiation occurred in the presence of metformin, suggesting a possible interaction between DPP-4 inhibitors and metformin.

Estimating Causal Effects of New Treatments Despite Self-Selection: The Case of Experimental Medical Treatments

Providing terminally ill patients with access to experimental treatments, as allowed by recent "right to try" laws and "expanded access" programs, poses a variety of ethical questions. While practitioners and investigators may assume it is impossible to learn the effects of these treatment without randomized trials, this paper describes a simple tool to estimate the effects of these experimental treatments on those who take them, despite the problem of selection into treatment, and without assumptions about the selection process. The key assumption is that the average outcome, such as survival, would remain stable over time in the absence of the new treatment. Such an assumption is unprovable, but can often be credibly judged by reference to historical data and by experts familiar with the disease and its treatment. Further, where this assumption may be violated, the result can be adjusted to account for a hypothesized change in the non-treatment outcome, or to conduct a sensitivity analysis. The method is simple to understand and implement, requiring just four numbers to form a point estimate. Such an approach can be used not only to learn which experimental treatments are promising, but also to warn us when treatments are actually harmful - especially when they might otherwise appear to be beneficial, as illustrated by example here. While this note focuses on experimental medical treatments as a motivating case, more generally this approach can be employed where a new treatment becomes available or has a large increase in uptake, where selection bias is a concern, and where an assumption on the change in average non-treatment outcome over time can credibly be imposed.

Implications of Removing Rosiglitazone's Black Box Warning and Restricted Access Program on the Uptake of Thiazolidinediones and Dipeptidyl Peptidase-4 Inhibitors Among Patients with Type 2 Diabetes

BACKGROUND

Medications are increasingly being approved with limited, short-term evidence regarding safety. Regulatory safety concerns may emerge for these drugs but later may be reversed if additional evidence suggests no warning is indicated.

OBJECTIVE

To describe trends over time in the initiation of rosiglitazone and pioglitazone-both in the thiazolidinedione (TZD) class-and medications from the dipeptidyl peptidase-4 (DPP-4) inhibitor class before and after the FDA removed a black box warning and restricted access program for rosiglitazone regarding an increased risk of myocardial infarction.

METHODS

This retrospective study evaluated initiation of TZDs and DPP-4 inhibitors using 2001-2015 administrative claims data from a U.S. commercially insured population. Patients were aged 18-64 years and were new users of either a TZD or DPP-4 inhibitor. Among all patients who were new users of either a TZD or a DPP-4 inhibitor during each quarter-year (Q), the percentage of patients who initiated rosiglitazone, pioglitazone, and DPP-4 inhibitors were calculated.

RESULTS

There were 630,977 patients eligible for the study. During 2007, rosiglitazone initiators decreased from 39.1% to 8.0% in 2007 Q4 when the black box warning was implemented. During 2010, rosiglitazone initiators decreased from 7.6% to 1.0%, as safety evidence accumulated and the restricted access program requirement was announced. Rosiglitazone initiation remained below 1.0%, even after regulatory restrictions were removed in November 2013. Pioglitazone initiation decreased from 46.4% in 2010 Q1 to 14.8% in 2011 Q4 and remained relatively constant between 14.5% and 17.8% after regulatory restrictions for rosiglitazone were removed. After DPP-4 inhibitors first became available in 2006 Q3, initiation of this medication class increased rapidly, stayed relatively constant between 42.8% and 45.5% in 2009, and then quickly rose and remained above 80% from 2012 through 2015.

CONCLUSIONS

This case study provides some evidence that adding and later reversing drug safety warnings-particularly those with restricted access requirements-may affect the uptake of the targeted product into the population when multiple clinically relevant treatment alternatives are available (such as type 2 diabetes). Once a treatment falls out of favor, removal of safety warnings and/or restricted access programs may not lead to increased use.

DISCLOSURES

This project was not directly supported by any funding. Hickson was supported by the National Heart, Lung, and Blood Institute through a National Research Service Award (NRSA) training grant (4T32HL007055-41) as a postdoctoral research fellow with the Cardiovascular Disease Epidemiology Program at The University of North Carolina at Chapel Hill (UNC-CH). Cole was supported by a NRSA Predoctoral Traineeship from the Agency for Healthcare Research and Quality sponsored by The Cecil G. Sheps Center for Health Services Research, UNC-CH (grant no. T32-HS000032) and a predoctoral fellowship from the American Foundation for Pharmaceutical Education. Unrelated to this project, Cole was a part-time employee of Truven Health Analytics/IBM Watson Health. Dusetzina has nothing to disclose.