Of all activities in general practice, prescribing has the greatest potential to produce health benefits or harm, the latter, particularly in the elderly. Among the many factors suggested to influence prescribing quality is socio-economic status.From July 1^st 2001, a change in government health policy in Ireland entitled all persons aged 70 and over to become eligible for the General Medical Services (GMS) Scheme irrespective of income and thus receive free medical and pharmaceutical services. Prior to this, eligibility for the GMS scheme was determined by means testing of income.

We compared the quality of prescribing, using prescribing indicators, between the relatively affluent ("new" n=25,945) and the relatively deprived ("old" n=62,254) over 70 year olds in the Eastern Region Health Authority (ERHA) in Ireland. We examined whether socio-economic status (as defined by GMS eligibility prior to and post July 2001) influenced the quality of prescribing between these patient groups during July 2001-June 2002.

Prescribing indicators (Beers 1997; Osborne et al 1997; Campell et al 2001) were applied to the prescription data and were classified as: (1) descriptive e.g. number of prescription items/patient (2) assessing potentially harmful prescribing (3) evidence based indicators e.g. secondary prevention therapies in ischaemic heart disease (IHD) patients. All prescription items were coded using the WHO Anatomical Therapeutic Classification (ATC). The results are expressed as odds ratio (OR) adjusted for gender and 95% confidence intervals using logistic regression. All analysis was carried out using the SAS statistical software package version 8 (SAS Institute Inc).

The "old" over 70's were more likely to be exposed to major polypharmacy ( 5 drugs; OR=1.63; 95% CI 1.56,1.70) and to receive potentially harmful drugs such as thioridazine (OR=2.0; 1.56,2.5), cerebral vasodilators (OR 1.54; 1.34,1.72) and long acting sulphonyulrea (chlorpropamide; OR=1.56; 1.30,1.95). In addition, a greater proportion of the "old" over 70's (32.8%) were prescribed cimetidine as a percentage of the total H₂ receptor antagonist compared to the "new" over 70's (27.3%; p<0.05). In terms of evidence based prescribing, old over 70's who had IHD (based on the co-prescription of nitrates and aspirin) were less likely to receive secondary prevention therapies such as statins (OR 0.78; 0.69, 0.86) and ACE inhibitors (OR 0.61; 0.50,0.75).

These results suggest that differences in socio-economic status (such as income) may influence the prescribing behaviour of physicians and subsequently the quality of prescribing. The less affluent would appear to receive more therapies, which may in part be attributable to greater morbidity, but the choice of agents and lesser use of secondary prevention may indicate a bias towards the more affluent. Indicators measuring the quality of prescribing may help improve the standard of care patients receive irrespective of income.

Beers MH. (1997) Arch Intern Med 47:948-9532.
Oborne CA et al (1997) Br J Clin Pharmacol 43:91-73.
Campbell SM et al (2000) BMJ 321:1-5.