Are recommendations for prescribing applied for older people with reduced kidney function in primary care? A mixed methods study to explore and improve implementation.

Background
Kidney function reduces with age, increasing the risk of harm and hospital admission from medicines. This project aimed to investigate the extent to which recommendations for prescribing drugs are applied for older people with reduced kidney function in primary care, and what needs to change to improve patient safety.
Research design and methods
A pragmatic sequential mixed methods design was used:
1. Cross-sectional case-note review.
2. Scoping literature review.
3. Primary Care Trust (PCT) wide cross-sectional survey of prescribing data.
4. GP interview study using the Theoretical Domains Framework.
5. Expert and stakeholder consensus group study.
Results
For 8 study drugs across a large PCT, a kidney function too low for recommended use was found for 3.5-39.6% in ≥65 year olds, and 24.2-79.5% in ≥85 years. The Cockcroft Gault equation provides a more accurate estimate of kidney function when prescribing for older people; 68.9-95.3% of patient drug events where kidney function was too low would have been missed if an estimated glomerular filtration rate had been used.
GPs expressed a lack of awareness and knowledge about prescribing when kidney function is reduced. Although they monitored kidney function, it was not thought of when prescribing. Not having warnings and prompts at medication review was a particular barrier identified by GPs, and that the British National Formulary information on prescribing in renal impairment information needs to be clarified.
The priorities for intervention and research agreed were to increase awareness of the need to assess kidney function in the prescribing process for older people, and to provide patient and drug specific warnings and prompts at medication review as well as initiation.
Conclusion
Many older people were taking medication that needed altering, or stopping, because of their reduced kidney function. This research has mapped the prevalence of inappropriate prescribing, and explored the behaviour determinants of GP prescribing, in reduced kidney function in primary care, identified what needs to change in practice, policy, and further research required, to improve patient safety.