Variability within general practitioner prescribing over time

Area of Science:

• Health Economics
• General Practice
• Pharmaceutical Policy

Background:

• General practitioner (GP) prescribing patterns exhibit variability over time.
• Understanding this intra-GP prescribing variability is crucial for accurate pharmaceutical budget forecasting.

Purpose of the Study:

• To quantify the intra-GP prescribing variability in New Zealand general practice.
• To analyze variability in prescription volume, total cost, and average item cost over time.

Main Methods:

• Longitudinal analysis of prescription data from two GP samples (regional and national) in New Zealand (1992-94).
• Utilized reimbursement data and PreMeC prescription analysis (PAS) data.
• Employed the coefficient of variation to measure intra-GP variability.

Main Results:

• Median intra-GP variability was 9% for total cost, 9% for volume, and 5% for average item cost (reimbursement data).
• Variability was higher with PAS data: 16% for cost, 17% for volume, and 8% for average item cost.
• Year-on-year variability was estimated at 9% for cost, 9-10% for volume, and 5-6% for average item cost.

Conclusions:

• Intra-GP prescribing variability is a significant factor in pharmaceutical cost and volume.
• Pharmaceutical budget estimates should incorporate an approximate 9% variability.
• Findings highlight the need for dynamic budgeting that accounts for prescribing fluctuations.