The impact of pay for performance on the control of blood pressure in people with chronic kidney disease stage 3-5

Background: The implementation of national estimated glomerular filatration rate reporting and the inclusion of renal-specific indicators in a primary care pay for performance (P4P) system since April 2006 has promoted identification and better management of risk factors related to chronic kidney disease (CKD). In the UK, the P4P framework is known as the Quality and Outcomes Framework (QOF). One of the key targets for intervention in primary care was hypertension. It is clear that hypertension is a major predictor of development and progression of CKD; thus, targeting better blood pressure control is likely to have a positive impact on outcomes in CKD. The aim of this study was to evaluate the effectiveness of renal indicators outlined in P4P on the management of hypertension in primary care. To estimate the cost implications of the resulting changes in prescribing patterns of antihypertensive medication following introduction of such indicators.

Methods: We performed a prospective cohort study using a large primary care database. This cohort was taken from a database collated as part of a clinical decision support system used to assist the management of CKD in primary care. We investigated a total population of 90 250 individuals on general practitioner (GP) registers with a valid serum creatinine estimation in the 6-year study period. A total of 10 040 patients had confirmed stage 3-5 CKD in the 2 years pre-QOF and formed the study cohort. Patients were studied over three time periods, pre-QOF (1 April 2004 to 31 March 2006), 2 years post-QOF (1 April 2006 to 31 March 2008) and finally the two subsequent years (1 April 2008 to 31 March 2010). The mean systolic and diastolic blood pressures (BP) together with antihypertensive medication were analysed over the three time periods. Cost calculation was based on 2009 British National Formulary list prices for antihypertensives.

Results: The mean age of the cohort at the start of the study period was 64.8 years, 55% were female. In those patients with stage 3-5 CKD 83.9% were hypertensive, defined by a pre-P4P BP of >140/85 or currently taking antihypertensive medication. The proportion of patients with CKD 3-5 attaining the BP target of 145/80 increased from 41.5% in the pre-QOF period to 50.0% in the post-QOF period. This increase was even more marked for those with hypertension in the pre-QOF period (28.8-45.1%). In the hypertensive patients, mean BP fell from 146/79 mmHg to 140/76 in the first 2 years post-P4P [P < 0.01, analysis of variance (ANOVA)]. This BP reduction was sustained in the last 2 years of the study, 139/75 (P < 0.01, ANOVA). The proportion of hypertensive patients taking angiotensin-converting enzyme inhibitors or angiotensin blockers increased, this was also sustained in the third time period. An increase in the prescribing of diuretics, calcium channel blockers and β-blockers was also observed. The additional cost of increased prescribing was calculated to be €25.00 per hypertensive patient based on GP prescription data.

Conclusions: Population BP control has improved since the introduction of P4P renal indicators, and this improvement has been sustained. This was associated with a significant increase in the use of antihypertensive medication, resulting in increased prescription cost. Longer-term follow-up will establish whether or not this translates to improved outcomes in terms of progression of CKD, cardiovascular disease and patient mortality.