Abstract
Background Many programmes to detect and prevent cardiovascular disease (CVD) have been performed, but the optimal strategy is not yet clear.
Aim To present a systematic review of cardiometabolic screening programmes performed among apparently healthy people (not yet known to have CVD, diabetes, or cardiometabolic risk factors) and mixed populations (apparently healthy people and people diagnosed with risk factor or disease) to define the optimal screening strategy.
Design and setting Systematic review of studies performed in primary care in Western countries.
Method MEDLINE, Embase, and CINAHL databases were searched for studies screening for increased cardiometabolic risk. Exclusion criteria were studies designed to assess prevalence of risk factors without follow-up or treatment; without involving a GP; when fewer than two risk factors were considered as the primary outcome; and studies constrained to ethnic minorities.
Results The search strategy yielded 11 445 hits; 26 met the inclusion criteria. Five studies (1995–2012) were conducted in apparently healthy populations: three used a stepwise method. Response rates varied from 24% to 79%. Twenty-one studies (1967–2012) were performed in mixed populations; one used a stepwise method. Response rates varied from 50% to 75%. Prevalence rates could not be compared because of heterogeneity of used thresholds and eligible populations. Observed time trends were a shift from mixed to apparently healthy populations, increasing use of risk scores, and increasing use of stepwise screening methods.
Conclusion The optimal screening strategy in primary care is likely stepwise, in apparently healthy people, with the use of risk scores. Increasing public awareness and actively involving GPs might facilitate screening efficiency and uptake.
INTRODUCTION
Cardiovascular diseases (CVD) are the leading causes of death and disability worldwide.1 Early detection and treatment of cardiometabolic risk factors can prevent development of CVD. GPs could play a central role in primary prevention as they are easily accessible to patients. Performing screening in a familiar setting — inside the general practice — is likely to enhance participation.2 In addition, counselling and treatment could easily follow screening, as these are already part of usual care.
Screening programmes can be performed among apparently healthy individuals (not yet known to have CVD, diabetes, or cardiometabolic risk factors) and in mixed populations (including apparently healthy people and people already diagnosed with a risk factor or established disease). Screening entire populations could lead to considerable unnecessary testing, with a fairly low yield, as most people screened will be healthy. Other ways of screening have been advocated, for example, targeted or stepwise screening methods.3 In targeted screening, a presumed high-risk group is considered, for example, people with central (abdominal) obesity. Stepwise methods can be used to identify high-risk groups, thereby limiting the number of people qualifying for further examinations.
Even though many screening programmes have been conducted in primary care over recent decades, no attempt had been made to compare the various approaches and define lessons. In the authors’ opinion, the optimal screening strategy should identify all people with an increased cardiometabolic risk, with a minimum effort to detect these people. Therefore, this study was a systematic review of cardiometabolic screening programmes in a primary care setting. The aim was to define the optimal screening strategy, by focusing on the population in which the screening was performed, the approach taken with patients, the different screening steps, the uptake, and the yield of screening.
METHOD
Criteria for considering studies for this review
In this study, the focus was on screening studies that were aimed at detecting an increased cardiometabolic risk, performed in primary care. Studies were excluded when they assessed only the prevalence of risk factors without further follow-up or treatment; those without involving a GP in the screening process; when fewer than two cardiometabolic risk factors (hypertension, dyslipidaemia, impaired glucose tolerance, diabetes, overweight/obesity) were considered as the primary outcome; and those with study populations constrained to an ethnic minority.
It was assumed that people with established disease or risk factors already receive extensive care through existing pathways, although this probably only applies to countries with a well-established primary care system. Therefore, only studies performed in Western countries were included: European countries, Australia, New Zealand, Canada, and the US.
How this fits in
Screening programmes can identify cardiometabolic risk factors that, when treated, can prevent development of cardiovascular disease. Several strategies, settings, and populations can be eligible. This study defines that the optimal screening strategy in primary care could be a stepwise approach, using, for example, risk scores to select people qualifying for further screening examinations. Increasing public awareness and actively involving GPs may facilitate screening efficiency and uptake.
Search methods
The MEDLINE, Embase, and CINAHL databases were searched for synonyms for primary care, screening, and cardiometabolic risk factors, on 27 January 2013. For the detailed search strategy see Appendix 1 (available from the authors on request). Language was restricted to English.
Data collection and analysis
Two reviewers independently checked all titles and abstracts. Potentially relevant articles were retrieved full-text, and subsequently assessed for inclusion by two reviewers independently. When a full-text article was not available, the author and/or editor was contacted. In cases of disagreement between two reviewers, these were discussed and resolved by the third reviewer.
For included studies, relevant data were extracted using a standardised template. Data were extracted on the screened population, screening method, patient approach, response rates, and yield of screening in terms of detected cardiometabolic risk factors. When more than one article reported on the same study population, the article with the most information on the method was included.
DISCUSSION
Summary
To the best of the authors’ knowledge, this is the first systematic review, having systematically searched and assessed the literature, of screening programmes to identify individuals with an increased cardiometabolic risk in primary care. The screening studies were published between 1967 and 2012. Over the past 50 years the attitude towards screening for an increased cardiometabolic risk has changed. Earlier studies focus on the benefits of screening, whereas later publications search for the best way to screen. With increasing knowledge of benefits of treating cardiometabolic risk factors, the cut-off values for the separate risk factors have become stricter.
A time trend in eligible populations was also observed. Not until 1995 was the first study focusing on an apparently healthy population published.12 In the last 8 years, four of the five existing studies on apparently healthy populations were performed and only two studies in mixed populations were published.19,20 This finding supports the authors’ assumption that people with established CVD, diabetes, hypertension, or dyslipidaemia already receive further risk assessment and treatment through existing pathways; therefore screening among them should not be necessary.
Most published screening programmes were performed in England; no studies were found performed in the US. This might be because of the requirement for actively involving GPs, as the GP has a less strong gatekeeper function in the US.
The first stepwise screening was published in 1993;22 the other three studies using a stepwise method were published in or after 2008.9,11,13 The latter studies all concerned apparently healthy populations. Particularly in these populations a stepwise method can be useful, as a substantial part of them will be healthy. A stepwise method will limit the number of people qualifying for elaborate examinations. A first step that requires action from the invited participants does not seem to influence the response rate compared with being invited for a total risk assessment at once. As only one study also invited a sample of people who did not qualify for further examinations after the first step, it was not possible to compare the discriminative ability of the different stepwise methods.
Sending reminders resulted in a higher screening uptake in apparently healthy populations. As expected, with an opportunistic approach the highest response rate was found with the longest study period.
Public awareness seems to be an important determinant of screening uptake. The highest response rate (93%) was found by Weinehall et al who describe the results of the first 8 years of the Västerbotten Intervention Programme in Sweden.27 The individual screening strategy was combined with a population strategy by creating a local health promotion collaboration to raise public awareness. The opportunistic screening by Cope et al lasted 1 week, but the screening uptake was 39%.4 The investigators advertised their health week in advance, within the general practice and by giving talks.
Devroey et al had an active approach but also the lowest response rate; people were invited by the local authorities to visit their GP for a health check.20 In most studies, people were invited by their GP; in no other study were the authorities responsible for inviting people. Six of the seven studies published in or after 2004 calculated a risk score; this reflects the increased use of risk scores in clinical practice. One might expect lower prevalence rates in an apparently healthy population than in a population with participants already diagnosed with risk factors. When comparing prevalence rates of hypertension, diabetes, or dyslipidaemia between healthy and mixed populations, no substantial differences were observed. From this, it can be concluded that a substantial part of the apparently healthy people have an increased cardiometabolic risk, which makes screening among this population worthwhile.
Strengths and limitations
Before discussing the yield of the screening programmes, some limitations of this systematic literature review need to be considered. As mentioned above, the cut-off values for risk factors have become stricter over the years, hindering the comparison of the yield over time. As a result of heterogeneity of used thresholds and risk scores, it was not possible to compare prevalence rates of cardiometabolic risk factors, nor relate the yield of the different studies to programme characteristics. Because most of the studies performed in mixed populations did not provide information about the composition of their study population, it was not possible to compare the yield of screening between healthy and mixed populations.
A systematic review often includes a risk of bias assessment of quality items like randomisation, selection bias, blinding, and loss-to-follow-up. The main interest in this study were cross-sectional aspects of screening; the focus was on the eligible population, screening method used, patient approach, response rate, and yield of screening. Because the focus was on ‘how’ rather than ‘how well’, no critical appraisal was performed on the above-mentioned items.
Another limitation of this study is that five articles were missed in the analyses as it was not possible to retrieve them full-text.
Comparison with existing literature
Ultimately, it is not the yield of the screening that makes sense, but the reduction of cardiovascular morbidity and mortality by early treatment of risk factors. Si et al examined the effect of screening versus no screening in general practice on surrogate endpoints, and found significant improvement in several cardiovascular risk factors, especially in high-risk populations.29 A Cochrane review, however, found no effect of health checks on total and cardiovascular mortality.30 The studies included in these reviews all started in the 20th century. As shown here, much has changed over the years, not only with regard to the characteristics of the screening programmes, but also with regard to new treatment insights.
Before implementing a screening programme it is first necessary to identify optimal programme efficiency, with regard to method and targeted population. This may influence the effects of screening on morbidity and mortality. In the authors’ opinion, the optimal screening strategy should identify all people with an increased cardiometabolic risk, with a minimum effort to detect these people. Defining ‘optimal’ in such a way, the authors realise that not all the Wilson and Jungner criteria are taken into account,31 such as cost-effectiveness, or psychological harm. Screening might reduce the costs for treating diseases, but screening programmes are also expensive. Therefore, it is important to use the available resources as efficiently as possible. A stepwise approach is likely to be the best way to reduce these costs through selection of a high-risk population, reducing the number of further examinations. Future research will have to prove whether stepwise screening methods are indeed more cost-effective.
Implications for research and practice
As people with established disease or risk factors are likely to receive extensive care through existing chronic care pathways, screening programmes should focus on apparently healthy people.
Stepwise methods can limit the number of people qualifying for further examinations; a stepwise method, in which the first step requires action from the invited participants, does not seem to influence response rate.
An invitation, and if necessary reminders, sent by the GP, appears to increase screening uptake.
Increased public awareness of the opportunity and relevance of screening seem to lead to a higher screening uptake.
In this review, 26 screening programmes are described for detecting people with an increased cardiometabolic risk, performed in primary care. Observed time trends were the shift in focus from a mixed population to an apparently healthy population, an increased use of risk scores, and an increasing use of stepwise methods, especially in apparently healthy populations.
In apparently healthy populations a substantial number of people were detected with an increased cardiometabolic risk, stressing the need for ongoing detection. Stepwise methods, increasing public awareness, and actively involving GPs could improve screening efficiency and uptake.
