Variation in the pharmaceutical costs of New Zealand general practices: a national database linkage study

J Public Health (Oxf). 2016 Mar;38(1):138-46. doi: 10.1093/pubmed/fdu116. Epub 2015 Jan 18.


Background: Variation in prescription costs between general practices and within practices over time is poorly understood.

Methods: From New Zealand's national health data collections, we extracted dispensed medicines data for 1045 general practices in 2011 and 917 practices continuously existing 2008-11. Using indirect standardization to account for patient demographics and morbidity, a standardized prescribing cost ratio (SPR: the ratio of actual : expected prescription costs) was calculated for each practice in each year. Case studies of three outlier clinics explored reasons for their status.

Results: SPRs ranged from 0.53 to 2.28 (median = 0.98). Of 469 practices with higher than expected costs (SPR > 1.0) in 2011, 204 (43.5%) had a single medicine or therapeutic drug class accounting for >15% of total costs. Case studies contrasted practices with overall pharmaceutical expenditure influenced strongly by a few patients needing high-cost medicines, more patients using medicines in one high-cost therapeutic drug class (antiretrovirals), and high medicine use across all therapeutic drug classes.

Conclusions: Routine data collections can measure inter-practice variation in prescription costs, adjusted for differences in the demography and morbidity profile of each practice's patients. Small groups of patients using high-cost medicines influence general practices' expenditure on pharmaceuticals.

Keywords: New Zealand; data collection; general practice; health expenditures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Child
  • Child, Preschool
  • Databases, Factual
  • Drug Costs / statistics & numerical data*
  • Female
  • General Practice / economics*
  • General Practice / statistics & numerical data
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Middle Aged
  • New Zealand
  • Prescription Drugs / economics
  • Sex Factors
  • Young Adult


  • Prescription Drugs