On the evaluation of drug benefits policy changes with longitudinal claims data: the policy maker's versus the clinician's perspective

Effects of a 3-Tier Pharmacy Benefit Design on the Prescription Purchasing Behavior of Individuals With Chronic Disease

OBJECTIVE

To evaluate the impact of 3-tier (copayment) pharmacy benefit structures on medication utilization behavior.

METHODS

A pretest-posttest quasi-experimental design was employed. Chronic disease sufferers (N=8,132) from a health plan were classified into the following groups: (a) 2-tier copayment moving to a 3-tier structure, ("converting" group), (b) 2-tier staying in a 2-tier structure and, (c) 3-tier staying in a 3-tier structure. The latter 2 were "comparison" groups. Two 7-month time periods were determined: the "preperiod" (June through December 2000) and the "postperiod" (January through July 2001) for a change in pharmacy benefit structure. Pharmacy claims data were used for data collection. Statistical analyses included bivariate tests to evaluate predifferences and postdifferences across study groups. Maximum likelihood estimates from a repeated measures model were used to examine changes in formulary compliance and generic use rates. Discontinuation of nonformulary medications was evaluated using logistic regression.

RESULTS

Controlling for demographics, number of comorbidities, disease state, and pharmacy benefit structure, the formulary compliance rate increased by 5.6% for the converting group. No significant increases were seen for the comparison groups. Generic use rates increased by 6 to 8 absolute percentage points for all groups (3.3% to 4.9 % adjusted rates). Converting group members were 1.76 times more likely to discontinue their nonformulary medication than those in the 2-tier comparison group and 1.49 times more likely than those in the 3-tier comparison group.

CONCLUSIONS

These findings suggest that shifting individuals from a 2-tier to a 3-tier drug benefit copayment structure resulted in changes in medication utilization. Decision makers need to balance these changes with the potential dissatisfaction that members may express in paying higher copayments.

DISCLOSURES

Funding for this research was provided by Merck and Company through the Academic Medicine and Managed Care Forum and was obtained by authors Kavita V. Nair, Robert J. Valuck, Pamela Wolfe, Julie M. Ganther, and Marianne M. McCollum. Nair served as principal author of the study. Study concept and design was contributed by Nair, Valuck, Wolfe, Ganther, McCollum, and author Sonya J. Lewis. Analysis and interpretation of data and drafting of the manuscript were primarily the work of Nair and Wolfe, and all authors contributed to the critical revision of the manuscript. Statistical expertise was contributed by Wolfe. Administrative, technical, and/or material support was provided by Mark Enders.

Near Real-time Surveillance for Consequences of Health Policies Using Sequential Analysis

BACKGROUND

New health policies may have intended and unintended consequences. Active surveillance of population-level data may provide initial signals of policy effects for further rigorous evaluation soon after policy implementation.

OBJECTIVE

This study evaluated the utility of sequential analysis for prospectively assessing signals of health policy impacts. As a policy example, we studied the consequences of the widely publicized Food and Drug Administration's warnings cautioning that antidepressant use could increase suicidal risk in youth.

METHOD

This was a retrospective, longitudinal study, modeling prospective surveillance, using the maximized sequential probability ratio test. We used historical data (2000-2010) from 11 health systems in the US Mental Health Research Network. The study cohort included adolescents (ages 10-17 y) and young adults (ages 18-29 y), who were targeted by the warnings, and adults (ages 30-64 y) as a comparison group. Outcome measures were observed and expected events of 2 possible unintended policy outcomes: psychotropic drug poisonings (as a proxy for suicide attempts) and completed suicides.

RESULTS

We detected statistically significant (P<0.05) signals of excess risk for suicidal behavior in adolescents and young adults within 5-7 quarters of the warnings. The excess risk in psychotropic drug poisonings was consistent with results from a previous, more rigorous interrupted time series analysis but use of the maximized sequential probability ratio test method allows timely detection. While we also detected signals of increased risk of completed suicide in these younger age groups, on its own it should not be taken as conclusive evidence that the policy caused the signal. A statistical signal indicates the need for further scrutiny using rigorous quasi-experimental studies to investigate the possibility of a cause-and-effect relationship.

CONCLUSIONS

This was a proof-of-concept study. Prospective, periodic evaluation of administrative health care data using sequential analysis can provide timely population-based signals of effects of health policies. This method may be useful to use as new policies are introduced.

An Evaluation of a Clinical Pre-Exposure Prophylaxis Education Intervention among Men Who Have Sex with Men

OBJECTIVE

To evaluate the impact of an HIV pre-exposure prophylaxis (PrEP) education intervention on PrEP awareness and use among men who have sex with men (MSM) attending a sexually transmitted diseases (STD) clinic.

DATA SOURCES/STUDY SETTING

Men who have sex with men STD clinic patients.

STUDY DESIGN

We estimated a difference-in-differences linear regression model, comparing MSM whose first visit to the clinic was before ("control") or after ("treatment") intervention implementation and controlling for patient.

DATA COLLECTION/EXTRACTION

We used self-reported data on PrEP awareness and use from STD clinic intake forms.

PRINCIPAL FINDINGS

Pre-exposure prophylaxis awareness between first and second clinic visits increased 27.2 percentage points (pp) in the treatment group, relative to 13.7 pp in the control group. Similarly, PrEP use increased 7.1 pp in the treatment group versus 2.4 pp in the control group. Based on adjusted estimates, the PrEP intervention increased PrEP awareness by 24 pp (p < .01) and PrEP use by 5 pp (p = .01), increases of 63 percent and 159 percent relative to the 6 months prior to the intervention.

CONCLUSION

A brief, scalable STD clinic PrEP education intervention led to significantly increased PrEP awareness and use among MSM. Health care providers should consider implementing brief PrEP education interventions in sexual health care settings.

A framework to evaluate the effects of small area variations in healthcare infrastructure on diagnostics and patient outcomes of rare diseases based on administrative data

INTRODUCTION

Small area variations in healthcare infrastructure may result in differences in early detection and outcomes for patients with rare diseases.

METHODS

It is our aim to provide a framework for evaluating small area variations in healthcare infrastructure on the diagnostics and health outcomes of rare diseases. We focus on administrative data as it allows (a) for relatively large sample sizes even though the prevalence of rare diseases is very low, and (b) makes it possible to link information on healthcare infrastructure to morbidity, mortality, and utilization.

RESULTS

For identifying patients with a rare disease in a database, a combination of different classification systems has to be used due to usually multiple diseases sharing one ICD code. Outcomes should be chosen that are (a) appropriate for the disease, (b) identifiable and reliably coded in the administrative database, and (c) observable during the limited time period of the follow-up. Risk adjustment using summary scores of disease-specific or comprehensive risk adjustment instruments might be preferable over empirical weights because of the lower number of variables needed.

CONCLUSION

The proposed framework will help to identify differences in time to diagnosis and treatment outcomes across areas in the context of rare diseases.

Medicare part D's impact on antipsychotic drug use and costs among elderly patients without prior drug insurance

Medicare part D's implementation improved access to and affordability of prescription drugs for the elderly without prior drug insurance. Effects for specific drugs and drug classes are less well understood. We assessed part D's impact on antipsychotic medication (APM) utilization and out-of-pocket costs among elderly without prior drug insurance. Retail pharmacy claims from 3 nationwide pharmacy chains were used to analyze 2 time-series designs: (1) a policy model, to obtain a policymaker's perspective: what was the overall impact of part D on APM use and costs among elderly without drug insurance in 2005 with the opportunity to enroll? And (2) a clinical model, to obtain a clinician's perspective: what would happen to elderly without drug insurance in 2005 who did enroll in part D--would they be able to get APMs? At what cost? Subgroup analyses among part D enrollees evaluated potentially different effects for patients who received a subsidy and patients who used antidementia drugs. In the policy model, part D implementation was associated with a 5% increase in APM use and a 37% reduction in out-of-pocket costs, suggesting a modest need for APMs among all previously uninsured elderly. Patients who did enroll in part D (clinical model) had a 97% increase in APM use and a 62% decrease in out-of-pocket costs, suggesting that patients who needed APMs were able to access them at low cost through the part D program. Part D implementation was associated with increased use and affordability of APMs for the elderly without prior drug insurance.

The impact of reference pricing on switching behaviour and healthcare utilisation: the case of statins in Germany

This paper analyses (1) the impact of the inclusion of statins in the German reference pricing scheme in 2005 on the statin market, and (2) the effect of switching behaviour subsequent to the policy change on healthcare utilisation and costs. Patients with prescriptions for statins in 2004 were observed for 1 year before and 1 year after the policy change, which went into effect on 1 January 2005. Data on outpatient and inpatient visits, pharmaceutical consumption, and cost to the sickness fund were collected from a sickness fund with more than 5.8 million insured members in 2005. Compared to patients who were not affected by the policy change, patients treated previously with atorvastatin experienced higher non-adherence and increased discontinuation of treatment (P < 0.0001). Compared to patients who continued treatment with atorvastatin (non-switchers), patients who switched to another statin were hospitalised more often (P = 0.0439). However, difference-in-differences in hospitalisation due to coronary heart disease (P = 0.8751) and emergency visits (P = 0.5624) did not differ significantly between the two groups. Patients who switched more than once experienced a significant increase in hospital visits (P = 0.0061) and hospital visits due to cardiovascular disease (P = 0.0096) compared to non-switchers. Difference-in-differences in outpatient healthcare utilisation did not differ between non-switchers and switchers. Total savings resulting from the policy change ranged from <euro> 94.4 million to <euro> 108.7 million. Although manufacturers usually comply with reference pricing by reducing their retail prices to the reference price, regulators have to be aware of the consequences in cases where manufacturers react as in this situation.

Good research practices for comparative effectiveness research: defining, reporting and interpreting nonrandomized studies of treatment effects using secondary data sources: the ISPOR Good Research Practices for Retrospective Database Analysis Task Force Report--Part I

OBJECTIVES

Health insurers, physicians, and patients worldwide need information on the comparative effectiveness and safety of prescription drugs in routine care. Nonrandomized studies of treatment effects using secondary databases may supplement the evidence based from randomized clinical trials and prospective observational studies. Recognizing the challenges to conducting valid retrospective epidemiologic and health services research studies, a Task Force was formed to develop a guidance document on state of the art approaches to frame research questions and report findings for these studies.

METHODS

The Task Force was commissioned and a Chair was selected by the International Society for Pharmacoeconomics and Outcomes Research Board of Directors in October 2007. This Report, the first of three reported in this issue of the journal, addressed issues of framing the research question and reporting and interpreting findings.

RESULTS

The Task Force Report proposes four primary characteristics-relevance, specificity, novelty, and feasibility while defining the research question. Recommendations included: the practice of a priori specification of the research question; transparency of prespecified analytical plans, provision of justifications for any subsequent changes in analytical plan, and reporting the results of prespecified plans as well as results from significant modifications, structured abstracts to report findings with scientific neutrality; and reasoned interpretations of findings to help inform policy decisions.

CONCLUSIONS

Comparative effectiveness research in the form of nonrandomized studies using secondary databases can be designed with rigorous elements and conducted with sophisticated statistical methods to improve causal inference of treatment effects. Standardized reporting and careful interpretation of results can aid policy and decision-making.

Effects of prescription coinsurance and income-based deductibles on net health plan spending for older users of inhaled medications

BACKGROUND

Health plans that increase prescription cost-sharing for their patients may increase overall plan costs. We analyzed the impact on health plan spending of a switch in public drug insurance from full coverage to a prescription copayment (copay), and then to income-based deductibles plus coinsurance (IBD).

METHODS

We studied British Columbia residents 65 years of age or older who were dispensed inhaled steroids, beta2 agonists or anticholinergics on or after January 1996. Multivariable linear regression was used to estimate health plan costs for the population using inhalers by the Ministry of Health (MOH) during the copay and IBD policies. We estimated costs for excess physician visits and emergency hospitalizations based on data from a previously published cohort study and cost data from the MOH. We estimated the net change in MOH spending as the sum of changes in spending for inhalers, physician visits, hospitalizations, and policy administration costs.

RESULTS

Net health plan spending increased by C$1.98 million per year during the copay policy [95% confidence interval (CI): 0.10-4.34], and C$5.76 million per year during the first 10 months of the IBD policy (95% CI: 1.75-10.58). Out-of-pocket spending by older patients increased 30% during the copay policy (95% CI: 24-36) and 59% during the IBD policy (95% CI: 56-63).

CONCLUSIONS

British Columbia's experience indicates that cost containment focused on cost-shifting to patients may increase net expenditures for the treatment of some diseases. Health plans should consult experts to anticipate the potential cross-program impacts of policy changes.

The effect of Medicare Part D coverage on drug use and cost sharing among seniors without prior drug benefits

This study evaluates the effect of Medicare Part D among seniors who previously lacked drug coverage, using time-trend analyses of patient-level dispensing data from three pharmacy chains. Of 114,766 seniors without drug benefits, 55 percent initiated drug insurance under Part D. After the penalty-free Part D enrollment period, use of statins, clopidogrel, and proton pump inhibitors stabilized at levels ranging from 11 percent to 37 percent above the trend that would have been expected if Part D had not been implemented. Patients reaching the Part D coverage gap (12 percent) experienced a decrease in essential medication use ranging from 5.7 percentage points per month for warfarin to 6.3 percentage points for statins.

Bridging bench and practice: translational research for schizophrenia and other psychotic disorders

Translational research is urgently needed to turn basic scientific discoveries into widespread health gains and nowhere are these needs greater than in conditions such as schizophrenia and other psychotic disorders. In this article, we discuss one type of translational research--called T1--which is needed to take advantage of developments in the basic neurosciences and translate them into more efficacious diagnostic, preventive, and therapeutic interventions. However, ensuring that interventions from T1 research actually benefit patients will require a second form of translational research--called T2--to turn innovations into everyday clinical practice and health decision-making. Recent examples of T1 and T2 research in schizophrenia and other psychotic disorders as well as strategies for better linking T1 and T2 research agendas are covered.

Cardiovascular outcomes after a change in prescription policy for clopidogrel

BACKGROUND

Drug-reimbursement policies may have an adverse effect on patient outcomes if they interfere with timely access to efficacious medications for acute medical conditions. Clopidogrel in combination with aspirin is the recommended standard of care for patients receiving coronary stents to prevent thrombosis. We examined the population-level effect of a change by a Canadian provincial government in a pharmacy-benefits program from a prior-authorization policy to a less restrictive, limited-use policy on access to clopidogrel among patients undergoing percutaneous coronary intervention (PCI) with stenting after acute myocardial infarction.

METHODS

We conducted a population-based, retrospective, time-series analysis from April 1, 2000, to March 31, 2005, of all patients 65 years of age or older with acute myocardial infarction who underwent PCI with stenting in Ontario, Canada. The primary outcome was the composite rate of death, recurrent acute myocardial infarction, PCI, and coronary-artery bypass grafting at 1 year, with adjustment for sex and age. The secondary outcome was major bleeding.

RESULTS

The rate of clopidogrel use within 30 days after hospital discharge following myocardial infarction increased from 35% in the prior-authorization period to 88% in the limited-use period. The median time to the first dispensing of a clopidogrel prescription decreased from 9 days in the first period to 0 days in the second period. The 1-year composite cardiovascular outcome significantly decreased from 15% in the prior-authorization group to 11% in the limited-use group (P=0.02). Rates of bleeding in the two groups did not change.

CONCLUSIONS

The removal of a prior-authorization program led to improvement in timely access to clopidogrel for coronary stenting and improved cardiovascular outcomes.

Effects of a consumer driven health plan on pharmaceutical spending and utilization

OBJECTIVES

To compare pharmaceutical spending and utilization in a consumer driven health plan (CDHP) with a three-tier pharmacy benefit design, and to examine whether the CDHP creates incentives to reduce pharmaceutical spending and utilization for chronically ill patients, generic or brand name drugs, and mail-order drugs.

STUDY DESIGN

Retrospective insurance claims analysis from a large employer that introduced a CDHP in 2001 in addition to a point of service (POS) plan and a preferred provider organization (PPO), both of which used a three-tier pharmacy benefit.

METHODS

Difference-in-differences regression models were estimated for drug spending and utilization. Control variables included the employee's income, age, and gender, number of covered lives per contract, election of flexible spending account, health status, concurrent health shock, cohort, and time trend. Results. CDHP pharmaceutical expenditures were lower than those in the POS cohort in 1 year without differences in the use of brand name drugs. We find limited evidence of less drug consumption by CDHP enrollees with chronic illnesses, and some evidence of less generic drug use and more mail-order drug use among CDHP members.

CONCLUSIONS

The CDHP is cost-neutral or cost-saving to both the employer and the employee compared with three-tier benefits with no differences in brand name drug use.

What is required to evaluate the impact of pharmaceutical reference pricing?

OBJECTIVE

To describe empirical studies evaluating the impact of reference pricing (RP) interventions in pharmaceutical markets in order to discuss the requirements for these evaluations.

METHODS

Ten studies were included in this review. For each study, the nature of the intervention, the nature of the data available, the nature of the question to be answered and the requirements of the evaluation method were examined through a questionnaire. The most frequently used evaluation method was the conventional before-after estimator, and only three studies used the difference-in-differences method.

RESULTS

Nine studies evaluated a therapeutic RP system and one evaluated a generic RP system. All of the papers reported how the reference price level was established, but only one study directly reported the updating frequency and criteria of the RP system. In four studies, details of simultaneous interventions were not reported. There is no paper providing evidence on overall social welfare impact. Four papers estimated the impact of intervention on the consumer price of drugs covered by the RP system. Only one provided information about the impact on the price of related drugs not covered by the system. Three studies included an outcome variable for the use of health services. The impact of RP intervention on the level of competition in the market for those medicines covered by the system was reported in only three of ten papers.

DISCUSSION/CONCLUSION

Despite the rigorous effort made to evaluate the impact of RP policies in some countries, several limitations may affect both their internal validity (the nature of the data available, statistical problems common to non-experimental data, etc.) and their external validity (heterogeneity in the nature of the intervention).

Net Health Plan Savings From Reference Pricing for Angiotensin-Converting Enzyme Inhibitors in Elderly British Columbia Residents

BACKGROUND

Reference drug pricing (RP) is a cost-sharing strategy commonly used to control drug expenditures. Under RP, a benefit plan fully reimburses medications that are equally or less expensive than the reference price, and requires patients to pay the extra cost of therapeutically equivalent but higher priced drugs. Critics argued that drug plan savings are offset by administrative costs and increased spending on other health services.

OBJECTIVE

We evaluated net healthcare savings in beneficiaries >or=65 years from the perspective of the British Columbia provincial health insurance system after it applied RP to angiotensin-converting enzyme (ACE) inhibitors in 1997.

METHODS

We estimated savings in new users of antihypertensives after the start of RP plus associated administrative costs and savings from reductions in retail drug prices. Findings were integrated with earlier results on the consequences of RP on expenditures for drugs, physicians, and hospitalizations among all seniors who used ACE inhibitors before the introduction of RP.

RESULTS

During the first year after the implementation of RP, savings for continuous users were CAN dollars 6.0 million. Savings for new users were dollars 0.2 million. Approximately five sixths thereof were achieved by utilization changes and one sixth by cost shifting to patients. There were no savings through drug price changes. Administering RP cost dollars 0.42 million. Overall net savings were estimated to be dollars 5.8 million during the first year after the start of RP. The magnitude of these savings is equal to 6% of all cardiovascular drug expenditures in seniors. After 10 years, approximately 50% of savings will be achieved by new users.

CONCLUSION

We observed substantial net savings from RP for ACE inhibitors for the provincial health insurance system in British Columbia, although there were generous exemptions from the policy. In other jurisdictions, savings could be higher if drug prices decline after the start of reference pricing.

A decade of growth in public and private pharmaceutical expenditures: the case of Belgium 1990-1999

OBJECTIVE

To make a systematic, transparent, internationally comparable description of trends (1990-1999) in total, public and private (co-payment + out-of-pocket) spending on pharmaceuticals in Belgium.

SETTING

Belgium, a western European country, with a Bismarck-type universal coverage healthcare system. NATURE OF THE STUDY: Descriptive analysis of time-series.

METHODS

Collaborative data gathering effort between academic and private research institutes and IMS health.

RESULTS

Mean annual growth rate was 3.9% for total, 5.3% for public, and 2.0% for private drug expenditures (expressed in constant 1999 EUR). The ratio of public to private spending shifted from 53.4% to 60.3%. Of the private spending, one third was co-payment for reimbursed medication and two thirds was out-of-pocket payment for non-reimbursed medication.

CONCLUSION

Co-operation between several data gathering constituencies within one country was necessary to achieve completeness and detail in data collection on out-of-pocket payments for non-reimbursed medicines, and hence in total drug expenditures. Discrepancies were found between the estimate of the public/private mix and OECD health data 2000 for public drug spending.

Approaches to pharmacy benefit management and the impact of consumer cost sharing

BACKGROUND

Numerous mechanisms have been introduced to deliver prescription drug benefits while controlling pharmaceutical costs. An understanding of the most prominent mechanisms of benefit management is an important step in determining the most effective approach to take in future years.

OBJECTIVES

The aims of this review were to illustrate the mechanisms by which managed care has attempted to efficiently and equitably deliver pharmacy benefits and to discuss the impact of such programs, including consumer cost sharing.

METHODS

A review of the literature was conducted using the PreMedline and MEDLINE databases from the years 1966 to 2002, reference lists from relevant articles, and online sources, including news releases, conference materials, and pharmacy benefit management reports.

RESULTS

Numerous pharmacy benefit management tools and their impact on utilization, expenditures, and health outcomes are reviewed, including disease state management; utilization management (ie, quantity limitations and prior authorization); drug utilization review; formulary management (ie, open and closed); delivery systems (ie, retail and mail order); and mechanisms for implementing consumer cost sharing (ie, generic incentives, multitiered copayments, and co-insurance). Although there is some evidence to suggest that certain benefit management tools have been successful in reducing health plan expenditures, a more thorough investigation of their potential unintended consequences is needed.

CONCLUSIONS

Implementing adequate levels of consumer cost sharing is necessary if employers and health plans are to continue offering prescription drug benefits. It is important to remember, however, that quality health care cannot be forfeited for the sake of short-term cost savings.

Quasi-experimental longitudinal designs to evaluate drug benefit policy changes with low policy compliance

A causal relation between drug benefit policy change and the increase in adverse outcomes can be tested by comparing the experience of a group of patients affected by the policy vs. the (counterfactual) experience of the same patients if the policy had not been implemented. Because counterfactual experiences cannot be observed, it must be assumed that the counterfactual is correctly described by extrapolating from the same population's previous experience. The null hypothesis of no policy effect can be empirically tested using quasi-experimental longitudinal designs with repeated measures. If compliance to a policy is low, results may be biased towards the null, but a subgroup analysis of compliers may be biased by nonignorable treatment selection. Using the example of reference drug pricing in British Columbia we discuss assumptions for causal interpretations of such analyses, and provide supplementary analyses to assess and improve the validity of findings. Results from nonrandomized comparisons of subgroups defined by their compliance to a policy change should generally be interpreted cautiously, and several biases should be explored.

Outcomes of reference pricing for angiotensin-converting-enzyme inhibitors

BACKGROUND

In January 1997, reference pricing for angiotensin-converting-enzyme (ACE) inhibitors for patients 65 years of age or older was introduced in British Columbia, Canada. For medications within a specific class, insurance covers the cost up to the reference price, and patients pay the extra cost of more expensive medications. Although reference pricing may reduce the costs of prescription drugs, there is concern that patients may switch to less effective medications or stop treatment.

METHODS

We analyzed data from the Ministry of Health on all 37,362 residents of British Columbia who were 65 or older and were enrolled in the provincial health insurance program, received ACE inhibitors priced higher than the reference price of $27 a month in 1996, and were potentially affected by the new policy. We identified 5353 residents who switched to an ACE inhibitor not subject to cost sharing during the first six months and compared them with 27,938 residents who received only ACE inhibitors subject to cost sharing.

RESULTS

Reference pricing for ACE inhibitors was not associated with changes in the rates of visits to physicians, hospitalizations, admissions to long-term care facilities, or mortality. The probability of stopping antihypertensive therapy decreased as compared with the probability before the change in policy (relative risk, 0.76; 95 percent confidence interval, 0.65 to 0.89). Eighteen percent of patients who had been prescribed ACE inhibitors subject to cost sharing switched to lower-priced alternatives. As compared with patients who did not switch, those who did had a moderate transitory increase in the rates of visits to physicians (rate ratio, 1.11; 95 percent confidence interval, 1.07 to 1.15) and hospital admissions through the emergency room (rate ratio, 1.19; 95 percent confidence interval, 0.99 to 1.42) during the two months after switching, but not subsequently.

CONCLUSIONS

We found little evidence that when reference pricing for ACE inhibitors was introduced in British Columbia, patients stopped treatment for hypertension or that health care utilization and costs increased.

Prescription duration after drug copay changes in older people: methodological aspects

OBJECTIVES

Impact assessment of drug benefits policies is a growing field of research that is increasingly relevant to health care planning for older people. Some cost-containment policies are thought to increase noncompliance. This paper examines mechanisms that can produce spurious reductions in drug utilization measures after drug policy changes when relying on pharmacy dispensing data. Reference pricing, a copayment for expensive medications above a fixed limit, for angiotensin-converting enzyme(ACE) inhibitors in older British Columbia residents, is used as a case example.

DESIGN

Time series of 36 months of individual claims data. Longitudinal data analysis, adjusting for autoregressive data.

SETTING

Pharmacare, the drug benefits program covering all patients aged 65 and older in the province of British Columbia, Canada.

PARTICIPANTS

All noninstitutionalized Pharmacare beneficiaries aged 65 and older who used ACE inhibitors between 1995 and 1997 (N = 119,074).

INTERVENTION

The introduction of reference drug pricing for ACE inhibitors for patients aged 65 and older.

MEASUREMENTS

Timing and quantity of drug use from a claims database.

RESULTS

We observed a transitional sharp decline of 110% t a standard error of 30% (P = .02) in the overall utilization rate of all ACE inhibitors after the policy implementation; five months later, utilization rates had increased, but remained under the predicted prepolicy trend. Coinciding with the sharp decrease, we observed a reduction in prescription duration by 31% in patients switching to no-cost drugs. This reduction may be attributed to increased monitoring for intolerance or treatment failure in switchers, which in turn led to a spurious reduction in total drug utilization. We ruled out the extension of medication use over the prescribed duration through reduced daily doses (prescription stretching) by a quantity-adjusted analysis of prescription duration.

CONCLUSION

The analysis of prescription duration after drug policy interventions may provide alternative explanations to apparent short-term reductions in drug utilization and adds important insights to time trend analyses of drug utilization data in the evaluation of drug benefit policy changes.