6th October 2017, Volume 130 Number 1463

Thomas Robinson, Rod Jackson, Susan Wells, Andrew Kerr, Roger Marshall

Many international guidelines and national health policies for the prevention of cardiovascular disease (CVD) advocate using estimates of patients’ absolute CVD risk, generated from multifactor risk prediction equations, to inform…

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Summary

Ninety percent of New Zealanders who are in the NZ Guidelines target group have had a CVD risk assessment. There is little information on how this information is used by doctors and their patients. The decision to start cholesterol lowering medications (statins) might be driven mainly by cholesterol levels, or (as NZ Guidelines suggest) by a comprehensive assessment of the person’s overall risk. This paper suggests that the latter approach is more likely, but that the decision process is complex and takes into account other factors.

Abstract

Aim

Cardiovascular disease (CVD) risk assessment is commonly recommended in guidelines, but there is uncertainty about how clinicians use this information. Our objective was to understand how New Zealand primary care clinicians use CVD risk assessment estimates to inform new statin prescribing.

Method

We used a cohort of patients seen in primary care who have had a CVD risk estimated on the basis of a New Zealand modified Framingham risk equation. These patients were linked to national pharmaceutical dispensing records to determine new statin use in the following six months. Regression discontinuity and logistic regression analysis, and graphical approaches, were used to explore associations between estimated CVD risk and primary clinicians’ decisions to initiate statin treatment.

Results

There were 76,571 patients aged 35 to 75 who were not on a statin, had a first recorded CVD risk assessment between July 2007 and June 2011, and for whom national guidelines recommended management on the basis of estimated CVD risk. Statin dispensing increased with increasing CVD risk. There was no evidence of sudden jumps in the proportions of patients dispensed statins at guideline recommended treatment threshold values of 15% and 20% CVD risk (P=0.314 and 0.731). A logistic regression model using the CVD risk score predicted statin initiation better than models using lipid measures (Area Under the Curve 0.725 versus 0.682). However, further modelling and graphical analysis suggested clinicians were using a range of other information to inform the initiation of statins.

Conclusion

New Zealand primary care clinicians’ statin prescribing decisions appear to be influenced by patients’ predicted CVD risk. However, other factors are associated with increased statin dispensing independent of CVD risk score.

Author Information

Thomas Robinson, Health Systems, School of Population Health, University of Auckland, Auckland;
Rod Jackson, Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland; Susan Wells, Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland; Andrew Kerr, Cardiology, Middlemore Hospital, Auckland;
Roger Marshall, Epidemiology and Biostatistics, University of Auckland, Auckland.

Acknowledgements

The authors would also like to thank members of the PREDICT Māori Advisory Group and the PREDICT Pacific Advisory Group, as well as general practitioners, practice nurses and patients affiliated with contributing primary health organisations (PHOs). PREDICT was developed by a collaboration of clinical epidemiologists at the University of Auckland, IT specialists at Enigma Publishing (a private provider of online health knowledge systems), primary health care organisations, non-governmental organisations (New Zealand Guidelines Group, National Heart Foundation, Diabetes New Zealand, Diabetes Auckland), several district health boards and the Ministry of Health. The PREDICT software platform is owned by Enigma Publishing (PREDICT is a trademark of Enigma Publishing).

Correspondence

Dr Thomas Robinson, Health Systems, School of Population Health, University of Auckland, 261 Morrin Rd, Auckland 1072.

Correspondence Email

tomrobnz@gmail.com

Competing Interests

Dr Jackson reports grants from Health Research Council of NZ during the conduct of the study. Dr Wells reports grants from Health Research Council of New Zealand and The Stevenson Foundation during the conduct of the study; grants from Roche Diagnostics Ltd, and National Heart Foundation of New Zealand outside the submitted work. Dr Kerr reports grants from HRC during the conduct of the study.

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