Date of Award

2012

Document type

Thesis

Degree Name

PhD (Doctor of Philosophy)

First Supervisor

Professor Tom Fahey

Second Supervisor

Dr Kathleen Bennett

Third Supervisor

Dr Conor Teljeur

Keywords

Drug Prescriptions, Ireland, Inappropriate Prescribing, Aged.

Abstract

Objectives

This thesis aimed to assess indicators of prescribing appropriateness and efficiency in those aged > 70 years in Ireland by: (i) estimating the prevalence and cost of potentially inappropriate prescribing (PIP); (ii) estimating the potential cost savings, by applying clinical guidelines, for the PIP indicator with the highest prevalence rate; (iii) examining the variation in PIP between GPs; and (iv) assessing the association between PIP and adverse health outcomes.

Methods

A retrospective national population study determined the prevalence and cost of PIP in the national population aged > 70 years in Ireland in 2007 by applying a modified version of the recently developed Screening Tool of Older Person’s potentially inappropriate Prescriptions (STOPP) to the Health Services Executive Primary Care Reimbursement Services (HSE-PCRS) pharmacy claims database. The PIP indicator with the highest prevalence rate was identified and potential cost savings were estimated for a one year period by examining different scenarios in prescribing patterns according to clinical and cost-effectiveness guidelines. The variation between GPs in the prevalence of PIP and patient and GP characteristics associated with PIP were examined in a multilevel logistic regression model. A retrospective cohort study examined the association between PIP and adverse health outcomes (adverse drug events (ADEs), health related quality of life (HRQOL) and hospitalisation) in community dwelling older patients across 15 general practices.

Results

The prevalence of PIP was 36% in those aged > 70 years in 2007. PIP had a significant impact on the national prescribing budget in 2007 (9% of overall expenditure for those aged > 70 years). The most prevalent PIP indicator was the prescription of proton pump inhibitors at maximum therapeutic dosage > 8 weeks. Regular review of patients and implementation of generic substitution and step-down therapy offered substantial cost savings.

Ninety-eight percent of GPs had at least one patient with PIP. There was evidence of significant variation in PIP between GPs but after adjustment for patient level variables this variation was no longer significant.

The STOPP criteria were significantly associated with patient reported adverse health outcomes. The expected number of ADEs and hospitals visits increased by 21% and 35% respectively after adjusting for confounders. The mean HRQOL utility was also significantly lower and patients were twice as likely to be classified as vulnerable and at risk of death, functional decline and greater health service use.

Conclusion

There is a high prevalence of PIP in those aged ^ 70 years in Ireland with significant cost consequences. PIP was significantly associated with patient reported adverse health outcomes. Studies of PIP are important to facilitate the design of better interventions to improve medication safety in older patients.

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Comments

Submitted for the Award of Doctor of Philosophy (PhD) to the Royal College of Surgeons, 2012.

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