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Spillovers Within and Between Physicians: Evidence from a Randomized Overprescribing Letter in Medicare

Last registered on December 28, 2018

Pre-Trial

Trial Information

General Information

Title
Spillovers Within and Between Physicians: Evidence from a Randomized Overprescribing Letter in Medicare
RCT ID
AEARCTR-0003209
Initial registration date
September 20, 2018

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
September 21, 2018, 12:15 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
December 28, 2018, 11:59 AM EST

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Region

Primary Investigator

Affiliation
Columbia University

Other Primary Investigator(s)

PI Affiliation
Columbia University
PI Affiliation
Harvard T.H. Chan School of Public Health

Additional Trial Information

Status
In development
Start date
2015-04-20
End date
2021-01-01
Secondary IDs
Abstract
In a fragmented healthcare system, efforts to change a physician’s practice patterns for the publicly insured may have implications for healthcare delivery that go beyond just the targeted physicians and insurers. Specifically, these efforts could change how physicians treat privately insured patients, and they could also influence the practice patterns of other physicians through peer effects. In this work, we aim to generate credible estimates of these spillovers by exploiting a randomized intervention that sought to reduce antipsychotic prescribing to publicly insured older and disabled adults. The original trial sent letters to high volume prescribers of the antipsychotic quetiapine in Medicare. The letters contained a peer comparison message and warned prescribers that they were under review by Medicare, and they reduced antipsychotic prescribing to Medicare patients by 16% over two years. We will estimate two spillovers. First, using commercial insurance data, we will estimate the effect of the letters on antipsychotic prescribing in private insurance, a within-prescriber spillover. Second, using Medicare data linked to practice and referral data, we will estimate the effect on antipsychotic prescribing by peers of the original study physicians, a between-prescriber spillover.

Registration Citation

Citation
Barnett, Michael, Andrew Olenski and Adam Sacarny. 2018. "Spillovers Within and Between Physicians: Evidence from a Randomized Overprescribing Letter in Medicare." AEA RCT Registry. December 28. https://doi.org/10.1257/rct.3209-2.0
Former Citation
Barnett, Michael, Andrew Olenski and Adam Sacarny. 2018. "Spillovers Within and Between Physicians: Evidence from a Randomized Overprescribing Letter in Medicare." AEA RCT Registry. December 28. https://www.socialscienceregistry.org/trials/3209/history/39665
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
Placebo Arm: The placebo arm received a letter describing a coming rule in Medicare that required prescribers to enroll in Medicare. The placebo arm then received a correction letter clarifying the rule. None of the letters mentioned prescribing of quetiapine.

Treatment Arm: The treatment arm prescribers received three letters, spaced roughly 3 months apart, about their quetiapine prescribing. Each letter included a peer comparison message and a notification that the prescriber was under review by Medicare.
Intervention Start Date
2015-04-20
Intervention End Date
2015-10-20

Primary Outcomes

Primary Outcomes (end points)
Days of quetiapine supplied during the intervention period of April 20, 2015 to December 31, 2016
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
In the original randomized trial, an analysis was conducted to identify outlier general-care prescribers of quetiapine in Medicare Part D. This analysis identified 5,055 prescribers, and they were then randomly allocated to the treatment or the control group. These prescribers are the "original study prescribers". The treatment prescribers were sent peer comparison review letters about their quetiapine prescribing; the control prescribers were sent placebo letters about an unrelated regulation.
This follow-up analysis considers two forms of spillover effects of the original letters. First, we examine whether the intervention altered prescribing by original study prescribers to patients covered by commercial insurance. For this analysis, we compare commercial prescribing in the original treatment and control groups.
Second, we examine whether the intervention influenced Medicare prescribing by peers of the original study participants. Peers are defined as either members of the same group practice as the original study prescribers or as those who share patients with original study prescribers. For this analysis, we study the Medicare prescribing of peers of physicians in the original treatment and control groups, exploiting the random assignment of the original study participants as a source of exogenous exposure to peer effects.
Experimental Design Details
Randomization Method
In the original study: randomization done by computer (in Stata)
Randomization Unit
Prescriber
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
5,055
Sample size: planned number of observations
Spillovers onto commercial insurance: 5,055 Spillovers onto peers: TBD
Sample size (or number of clusters) by treatment arms
Spillovers onto commercial insurance: 2,528 control arm, 2,527 treatment arm
Spillovers onto peers: TBD
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB

Institutional Review Boards (IRBs)

IRB Name
Columbia University Human Research Protection Office
IRB Approval Date
2018-06-17
IRB Approval Number
AAAR9368(M00Y01)
Analysis Plan

Analysis Plan Documents

Commercial Insurance Analysis Plan 1 (Dec 28, 2018)

MD5: 66923ac438da51b283357e11bd2a7a5a

SHA1: 21b34b49c843826524918f6984909d31b1e59321

Uploaded At: December 28, 2018

Peer Effects Analysis Plan v1 (Dec 4, 2018)

MD5: e5b9c1e622ef2766bd2535e78395cecd

SHA1: bcaecc6284c84fb0082dc9c8427166bce5342074

Uploaded At: December 04, 2018

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials