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Effects of introducing then removing cost-sharing for drugs among people with schizophrenia in Quebec: A natural experiment. Eric Latimer, Ph.D . Canadian Health Economics Study Group May 27 2010. Co- authors. Willy Wynant , M.S. 1 Adonia Naidu, M.Sc. 2 Robin Clark, Ph.D. 3

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Effects of introducing then removing cost-sharing for drugs among people with schizophrenia in Quebec: A natural experiment

Eric Latimer, Ph.D.

Canadian HealthEconomicsStudy Group

May 27 2010

co authors
  • Willy Wynant, M.S.1
  • Adonia Naidu, M.Sc.2
  • Robin Clark, Ph.D.3
  • Ashok Malla, M.D.2,4
  • Erica Moodie, Ph.D.1
  • Robyn Tamblyn, Ph.D.1

1 Department of Epidemiology, Biostatstics and OccupationalHealth, McGill University

2 Douglas Mental HealthUniversity Institute

3 Department of Psychiatry, McGill University

4 FamilyMedicine and CommunityHealth, Center for Health Policy and Research, University of Massachusetts MedicalSchool

Acknowledgement: Michal Abrahamowicz for contribution to original study design

study funding
Study funding
  • Fonds de la recherche en santé du Québec
  • Disabling mental illness
    • Severalsubtypes
    • Positive and negativesymptoms
  • Usuallydevelopsaround 18 for males, 25 for females (plus or minus severalyears)
  • About 1% of the population
  • Help control positive symptoms (psychoticepisodes)
  • Reducere-hospitalisations
  • Significantside-effects
  • Ineffective for 20 to 30% of people withschizophrenia
introduction of cost sharing in august 1996
Introduction of cost-sharing in August 1996
  • For welfarerecipients and seniors
    • Welfarerecipients: ceiling of $50 per quarter
      • $16.67 per month for people with mental illness
  • Tamblyn et al. 2001:
    • Reduction in use of medications
    • Increase in adverse events (deaths, hospitalizations and nursing homes) and ER visits
consistent with other studies
Consistent withotherstudies
  • Ward et al. 06 (and others): Antipsychoticscompliance:
    • Hospitalisations
    • Suicides, mortality
  • Soumerai et al. 94: Capping prescriptions for people withschizophrenia in NH:
    • Antipsychotics
    • Emergency psychiatric services
    • Governmentcosts
selective removal of cost sharing in october 1999
Selectiveremoval of cost-sharing in October 1999
  • For welfarerecipientsclassified as disabled
  • Includes people withschizophreniaclassified as disabled, whotypically consume antipsychotics
  • No studies of effects of removingcost-sharing for antipsychoticsidentified
qualitative interviews1
Qualitative interviews
  • In 2004-2005, 23 interviews withpsychiatrists, nurses and social workerswereconductedat 8 different sites in 6 Québec cities or towns
  • Consumersconsidered, but not included for reasons of efficiency (many interviews needed to obtainrepresentativesample)
  • Urban and rural, teaching and non-teaching sites included
  • Questions on varioustopics, including of relevance here: Effects of introducing, thenremovingcost-sharing on people withschizophrenia
main comments from qualitative interviews
Main commentsfrom qualitative interviews
  • Someschizophrenia patients more closelyfollowedthanothers – cost-sharing would have bigger impact on them
  • Removal of cost-sharing expected to have smaller impact
  • Re-evaluate impact of introducingcost-sharing on use of medications, for people withschizophrenia, withlargersample
  • Evaluate impact of removingcost-sharing 39 monthslater
identification of patients
Identification of patients
  • Data extracted for people who had at least one prescription of antipsychotics between Jan, 1st 1993 and Dec, 31st2004 while on welfare status
    • 107,005 individuals
  • Extracted from RAMQ:
    • Welfare status
    • Prescription data (DIN, duration, dose, charge, etc.)
    • Medical service data (type of service, Dx, etc.)
  • Extracted from Med-Echo:
    • Hospitalization data (Adm. & discharge dates, Dx, etc.)
data cleaning procedures on prescription data
Data cleaning procedures on prescription data
  • Conservative methods to ensure that all the corrections are plausible.
    • When a value seems incorrect, either:
      • At least 2 arguments concur to correct a value and we make this correction
      • Or we drop this prescription
    • Focus on cost, quantity and duration fields
numbers of prescriptions affected by data cleaning based on 03 and 04 data only
Numbers of prescriptions affected by data cleaning (based on 03 and 04 data only)
  • Problems of duration of prescription (number of days) = 0

& quantity of drug (i.e., total number of pills or ml) = 0

& drug cost = 0 when all not equal to zero but at least one equal to zero

 442 (0.02%) prescriptions are concerned

  • Duration of prescription > 270 days

 131 (0.01%) prescriptions, only 7 could be corrected

  • Problem with the ratio cost to quantity

 91 (<0.01%) prescriptions were concerned, no one could be corrected

  • Problem of low dose

 34 (<0.01%) prescriptions were concerned, only 4 could be corrected

Patients with prescriptions that could not be corrected were eliminated from the study

adjustments of the prescriptions why
Adjustments of the prescriptions: why?
  • If we draw successions of prescriptions for some patients we observe different patterns:

Jan, 1st

Jan, 15th


2 prescriptions of the same DIN:

Jan, 1st

Could be

Pills are lost

Jan, 14th

Jan, 1st


Jan, 25th

Jan, 12th

interpreted as

Jan, 12th


2 pills these days

bases for adjustment of the prescription start dates and durations
Bases for adjustment of the prescription start dates and durations
  • Consulted community pharmacist near Douglas Institute
  • A renewal less than 20% ahead of end of previous prescription is assumed to be an early refill
  • But, since a pharmacist must justify to the RAMQ why s/he would have accepted to fill a renewal prescription if the patient asks for a refill more than 20% too early, we do not do this automatically in such a case.
    • Consecutive refills that are more than 20% too early suggest a problem – normally such events, if accepted by the pharmacist, are rare (e.g., going on vacation, lost pills)
    • It could be an increase in dose
    • It could be an early renewal, concurrent with a new prescription, to synchronize the prescriptions
adjustment of the prescriptions algorithm
Adjustment of the prescriptions: algorithm
  • Two prescriptions of the same DIN and the same dosage overlapped (even by more than 20%): we moved the start date of the prescription forward, to make the prescription begin when the previous one ended

Except if it was a too early renewal for the second time: we supposed that this prescription began when it was filled and that the remaining pills were lost.

  • Synchronized prescriptions = if there was a synchronization (two or more DINs filled on the same day) the prescription was considered as beginning when filled and the previous one was stopped (considered as if the pills were lost)
adjustments of the prescriptions hospitalizations
Adjustments of the prescriptions: hospitalizations
  • Sometimes a patient was supposed to fill a prescription during a hospitalization (even when the hospitalization was for a psychiatric reason).
    • We supposed that all these pills were lost
  • When a hospitalization occurred at a time when the patient was on a prescription we supposed that all the pills from that prescription were not taken anymore and were considered as lost
construction of the cohort
Construction of the cohort
  • On welfare from 1993 to 2004 (ignoring interruptions < 1 month)
  • 18+ in 1995 and alive in 2004
  • At least one prescription of antipsychotics every 180 days from Jan 1st 1993 to July 31st1996, removing hospitalization days
  • Schizophrenia Dx either on hospitalization records OR medical records one or more times in the period 1993 – July 31st1996
  • N=4,401
proportion of days in month patient had access to antipsychotics
Proportion of days in month patient had access to antipsychotics
  • Proportion of days in month that antipsychotics available while in community
    • Adjustment for hospitalisations
  • < 10 days in community : Proportion undefined
first 9 months of 1993 excluded
First 9 months of 1993 excluded
  • No data from 1992
  • Don’t know when 1992 prescriptions end
  • Maximum prescription duration is 9 months
estimation strategy
Estimation strategy
  • Test for fixedeffects or randomeffects
  • Allow for differentintercepts, linear and quadratic time trends duringpre-cost-sharing, cost-sharing, and post-cost-sharing periods

Average APR in 6 months prior to cost-sharing introduction minus average APR in 6 months after cost- sharing introduced(N=4401)

Median difference= 0.005 Mean difference= 0.046


Average APR during 6 months after cost- sharing

removed minus average APR during 6 months prior

to cost-sharing removal (N=4401)

Median difference= 0 Mean difference= .0174596

hausman test
Hausman test
  • Rejectedat p<0.01
    • Use fixedeffects
sensitivity analysis
  • Remove values 3 monthsbefore and 3 monthsafter August 1 1996 and October 1 1999
    • To mitigateanyeffects of stockpiling or delayingpurchasing of medications in anticipation of policy change
  • Resultsqualitativelysimilar
  • High-stability group: Permanent reduction in APR, smalleffect of removingcost-sharing
  • Other groups:
    • Long-term trends towardsincreasedconsumption
    • Apparentlygreatereffect of removingcost-sharing
  • Non-experimental design: possible confounding
  • CV classification crude
  • SchizophreniaDx identification
  • Fixedcohort – drop-outs (welfare exit, death) ignored, possible bias
  • Removingcost-sharing was effective policy
  • Permanent effect of havingintroducedcost-sharing – especially for highstability group
  • Furtherevidencethatcost-sharing for antipsychoticsundesirable