Strengths and limitations of the study
The greatest strength of this pragmatic trial is that it gives evidence of effectiveness of cardiovascular risk management in day-to-day clinical practice. In addition, the large sample size ensured that those patients included were representative of the GP population. Furthermore, no dropout took place among the participating healthcare centres. Following this trial, five of the six centres continued to employ practice nurses for cardiovascular risk management.
The study also has limitations. First, it is limited to patients with a risk of at least 10% on the SCORE function,7 whereas the Dutch guideline for cardiovascular risk management suggested treatment at 5%.5 This is due to the previous studies in the region,16,25,26 where high-risk patients with at least 20% on the Framingham scale were selected, as it had been argued that high-risk patients will benefit most from preventive strategies.9
Second, post-randomisation exclusion took place while information about the exclusion criteria was not always available before initial assessment. It was decided not to randomise patients after passing the inclusion criteria because otherwise the practice nurse group would have to visit the centre twice, and this would have meant asking too much of patients. The difference in exclusion rates between the groups (53% versus 61%) might be slightly suspect. However, of all the exclusion criteria, only ‘diabetics’ and ‘other reasons’ (Figure 1) might have been influenced by the study group, because of the more systematic treatment by the practice nurse. Because the baseline characteristics of the study groups are the same, risking bias in the analyses is not expected.27
The third limitation of the study is that smoking behaviour and BMI were partly self-reported, mostly in the GP group. This could be considered a limitation, but the notion of poor reliability of self-reported smoking history was contradicted by a meta-analysis in which the sensitivity was found to be 88% and the specificity 89%.28 For BMI, a significant correlation between self-reported and recorded values was found (P<0.01); this is also confirmed by other studies.29 Self-reported weight in the GP group was corrected with a factor of 1.011.
Fourth, the intervention was directed at healthcare centres, with the result that some transfer of effect from the practice nurse to the GP might have taken place, resulting in reduced effectiveness. However, since 2006, much attention has been paid to cardiovascular prevention in primary care by Dutch medical and patient organisations, the government, and the Dutch Heart Foundation.30
Finally, the results will depend on the individual experiences of GPs and practice nurses who cooperated in the trial. Most GPs in this trial were already acquainted with risk management, while this task is new for practice nurses. It is therefore expected that, in the future experienced practice nurses will be achieving even better health outcomes than found in the present trial.
Comparison with existing literature
A recent Australian review on the efficacy of practice nurses for cardiovascular prevention has also shown improved results for cholesterol, blood pressure, and weight.31 Similar conclusions were drawn in the EuroAction survey, partly focusing on primary prevention by practice nurses for patients with ≥5% risk,7 and for their families.23 Other studies on nurse-led secondary prevention in primary care show similar results.32,33
No difference was found in patient characteristics between the participants and the non-attenders, although more missing measurements were found among males and older people. This finding corresponds with other studies: low blood pressure control is associated with increasing age, male sex, low education, non-white race, previous CVDs, living alone, decreased physical activity, or depression.34,35
Many high-risk patients did not achieve the treatment targets for the risk factors. The proportion is comparable with data from the Dutch Heart Foundation,36 and the EUROASPIRE studies.37 Comparison of the study population with data from the Registration Network Family Practices of Maastricht University Medical Centre reveals a similar distribution of sex and age.38
In the present study, patients received a postal invitation from the healthcare centre for risk assessment. Although this is not common in primary care in the Netherlands, the response rate was high: 83% and 75% of the patients had lipids and blood pressure measured at initial and final assessment. This is comparable with the 70% attendance rates in response to invitations by the national prevention programme for influenza, breast cancer, and cervical cancer.39
Implications for future research and clinical practice
The present findings support the involvement of practice nurses in cardiovascular risk management at the primary care level in the Netherlands. Because of the high and increasing volume of patients requiring cardiovascular risk management, this finding is likely to have important implications nationally for the organisation of primary care cardiovascular prevention. As many patients still did not achieve the treatment targets, cardiovascular risk management should be improved. Research is needed into the improvement and long-term effect of cardiovascular risk management, with a focus on reaching non-attenders and decreasing the patient dropout rate.