Correspondence
Non-diabetic patients (n=64)
Diabetic patients (n=64)
ACC/AHA calculator vs other calculators3
64·4% (65·6)
65·2% (60·2)
Overall agreement among 25 calculators (18 for diabetics) excluding the ACC/AHA calculator2
64·3% (64)
72·6% (73)
Reynold’s Risk Score
82·8%
N/A
UK Prospective Diabetes Study
71·9%
81·3%
QRISK2-2011
78·1%
87·5%
Calculators with >75% categorisation agreement in either non-diabetics or diabetics with the ACC/AHA calculator
Australian Absolute CVD Risk
79·7%
76·6%
New Zealand CV Risk Charts
81·3%
78·1%
Australian Risk Charts
87·5%
73·4%
New Zealand Know Your Numbers
79·7%
57·8%
PROCAM (Health Check)
65·6%
79·7%
Data are average (median) or average. ACC/AHA=American College of Cardiology/American Heart Association.
Table: Agreement of the ACC/AHA risk calculator with a sample of other commonly used risk calculators
might well be, but how does this new calculator compare with other similar calculators? We decided to compare how this new calculator categorises patients into risk levels compared with other commonly used cardiovascular disease risk calculators. We used risk categorisation data from our previous study3 of 25 calculators in which 128 standardised patients over a broad range of risk (each of seven risk factors variably dichotomised to high and low values) were categorised and we compared these data with the risk categorisation obtained if one used the ACC/AHA calculator. To allow for easy comparison, we used the standard 10-year risk categories of less than 10%, between 10% and 20%, and more than 20%. The calculator agreement results are shown in the table. For non-diabetic patients, the agreement of the ACC/AHA calculator was very similar to the risk categorisation agreement for all calculators. For patients with diabetes, the average agreement was 7% lower and the median agreement 13% lower, with a tendency to assign lower risk slightly more often than would most other calculators. It seems that the ACC/AHA risk calculator categorises patients in a similar way to many of the other available calculators. www.thelancet.com Vol 383 February 15, 2014
Importantly, calculations of risk are estimates and categorisations are relatively arbitrary. Any risk estimate should only be used as a tool to facilitate the initial discussion of benefits and harms of treatments as part of shared decision making. We declare that we have no conflicts of interest.
*James McCormack, Hoan Linh Banh, G Micheal Allan [email protected] University of British Columbia, Faculty of Pharmaceutical Sciences, Vancouver V6T1Z3, BC Canada (JMcC); and Department of Family Medicine, University of Alberta, Edmonton, AB, Canada (HLB, GMA). 1
2
3
Ridker PM, Cook NR. Statins: new American guidelines for prevention of cardiovascular disease. Lancet 2013; 382: 1762–65. Goff DC, Lloyd-Jones DM, Bennett G, et al. 2013 ACC/AHA guideline on the assessment of cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2013; published online Nov 13. DOI:10.1016/j.jacc.2013.11.005. Allan GM, Nouri F, Korownyk C, Kolber MR, Vandermeer B, McCormack J. Agreement among Cardiovascular Risk Calculators. Circulation 2013; 127: 1948–56.
The Comment by Paul Ridker and Nancy Cook1 concerning the new American Heart Association (AHA) and American College of Cardiology (ACC) guidelines deserves comment, primarily for the issues not discussed. The main problem with the new AHA/ ACC guidelines is that they are based on randomised controlled trials (RCTs),
all of which are affected by selection bias. This selection bias is a necessity of the RCT, which has to involve highrisk individuals, who are highly likely to sustain an atherothrombotic disease event within the trial timeframe. As a result, the findings of any RCT cannot be generalised to the population as a whole. This adds confusion to the primary prevention of atherothrombotic disease because the observational studies, which the AHA/ACC guidelines have disregarded, involve all comers and thus are more likely to involve a cohort that is much more representative of the entire population and to involve primary rather than secondary prevention scenarios. The abandonment of the low-density lipoprotein (LDL)-cholesterol goals of therapy seems foolish. The AHA/ACC guidelines seem to involve giving an arbitrary dose of statin and hoping for the best. As a result, some patients will be overtreated whereas others will be undertreated. If the patient has had his or her dyslipidaemia long enough, he or she will have subclinical atherothrombotic disease and will need dyslipidaemia therapy sufficient to attain an LDL-cholesterol level of 2·0 mmol/L if the precipitation method of high-density lipoprotein (HDL)cholesterol determination is used, but 1·8 mmol/L if the enzymatic method of HDL-cholesterol measurement is used.2 If the patient has only had his or her dyslipidaemia a relatively short time, he or she could probably be treated to lesser goals.3 Because this question is not answerable in most cases, the former goal would seem to be the safest. I declare that I have no conflicts of interest.
William E Feeman Jr [email protected] The Bowling Green Study, Bowling Green, OH43402, USA 1
2
3
Ridker PM, Cook NR. Statins: new American guidelines for prevention of cardiovascular disease. Lancet 2013; 382: 1762–65. Feeman WE. LDL lowering: evidence for a plaque non-progression threshold. Int J Cardiovasc Res 2013; 2: 5. Feeman WE Jr. Prediction of the population at risk of atherothrombotic disease. Exp Clin Cardiol 2004; 9: 235–41.
599
Non-diabetic patients (n=64)
Diabetic patients (n=64)
ACC/AHA calculator vs other calculators3
64·4% (65·6)
65·2% (60·2)
Overall agreement among 25 calculators (18 for diabetics) excluding the ACC/AHA calculator2
64·3% (64)
72·6% (73)
Reynold’s Risk Score
82·8%
N/A
UK Prospective Diabetes Study
71·9%
81·3%
QRISK2-2011
78·1%
87·5%
Calculators with >75% categorisation agreement in either non-diabetics or diabetics with the ACC/AHA calculator
Australian Absolute CVD Risk
79·7%
76·6%
New Zealand CV Risk Charts
81·3%
78·1%
Australian Risk Charts
87·5%
73·4%
New Zealand Know Your Numbers
79·7%
57·8%
PROCAM (Health Check)
65·6%
79·7%
Data are average (median) or average. ACC/AHA=American College of Cardiology/American Heart Association.
Table: Agreement of the ACC/AHA risk calculator with a sample of other commonly used risk calculators
might well be, but how does this new calculator compare with other similar calculators? We decided to compare how this new calculator categorises patients into risk levels compared with other commonly used cardiovascular disease risk calculators. We used risk categorisation data from our previous study3 of 25 calculators in which 128 standardised patients over a broad range of risk (each of seven risk factors variably dichotomised to high and low values) were categorised and we compared these data with the risk categorisation obtained if one used the ACC/AHA calculator. To allow for easy comparison, we used the standard 10-year risk categories of less than 10%, between 10% and 20%, and more than 20%. The calculator agreement results are shown in the table. For non-diabetic patients, the agreement of the ACC/AHA calculator was very similar to the risk categorisation agreement for all calculators. For patients with diabetes, the average agreement was 7% lower and the median agreement 13% lower, with a tendency to assign lower risk slightly more often than would most other calculators. It seems that the ACC/AHA risk calculator categorises patients in a similar way to many of the other available calculators. www.thelancet.com Vol 383 February 15, 2014
Importantly, calculations of risk are estimates and categorisations are relatively arbitrary. Any risk estimate should only be used as a tool to facilitate the initial discussion of benefits and harms of treatments as part of shared decision making. We declare that we have no conflicts of interest.
*James McCormack, Hoan Linh Banh, G Micheal Allan [email protected] University of British Columbia, Faculty of Pharmaceutical Sciences, Vancouver V6T1Z3, BC Canada (JMcC); and Department of Family Medicine, University of Alberta, Edmonton, AB, Canada (HLB, GMA). 1
2
3
Ridker PM, Cook NR. Statins: new American guidelines for prevention of cardiovascular disease. Lancet 2013; 382: 1762–65. Goff DC, Lloyd-Jones DM, Bennett G, et al. 2013 ACC/AHA guideline on the assessment of cardiovascular risk: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2013; published online Nov 13. DOI:10.1016/j.jacc.2013.11.005. Allan GM, Nouri F, Korownyk C, Kolber MR, Vandermeer B, McCormack J. Agreement among Cardiovascular Risk Calculators. Circulation 2013; 127: 1948–56.
The Comment by Paul Ridker and Nancy Cook1 concerning the new American Heart Association (AHA) and American College of Cardiology (ACC) guidelines deserves comment, primarily for the issues not discussed. The main problem with the new AHA/ ACC guidelines is that they are based on randomised controlled trials (RCTs),
all of which are affected by selection bias. This selection bias is a necessity of the RCT, which has to involve highrisk individuals, who are highly likely to sustain an atherothrombotic disease event within the trial timeframe. As a result, the findings of any RCT cannot be generalised to the population as a whole. This adds confusion to the primary prevention of atherothrombotic disease because the observational studies, which the AHA/ACC guidelines have disregarded, involve all comers and thus are more likely to involve a cohort that is much more representative of the entire population and to involve primary rather than secondary prevention scenarios. The abandonment of the low-density lipoprotein (LDL)-cholesterol goals of therapy seems foolish. The AHA/ACC guidelines seem to involve giving an arbitrary dose of statin and hoping for the best. As a result, some patients will be overtreated whereas others will be undertreated. If the patient has had his or her dyslipidaemia long enough, he or she will have subclinical atherothrombotic disease and will need dyslipidaemia therapy sufficient to attain an LDL-cholesterol level of 2·0 mmol/L if the precipitation method of high-density lipoprotein (HDL)cholesterol determination is used, but 1·8 mmol/L if the enzymatic method of HDL-cholesterol measurement is used.2 If the patient has only had his or her dyslipidaemia a relatively short time, he or she could probably be treated to lesser goals.3 Because this question is not answerable in most cases, the former goal would seem to be the safest. I declare that I have no conflicts of interest.
William E Feeman Jr [email protected] The Bowling Green Study, Bowling Green, OH43402, USA 1
2
3
Ridker PM, Cook NR. Statins: new American guidelines for prevention of cardiovascular disease. Lancet 2013; 382: 1762–65. Feeman WE. LDL lowering: evidence for a plaque non-progression threshold. Int J Cardiovasc Res 2013; 2: 5. Feeman WE Jr. Prediction of the population at risk of atherothrombotic disease. Exp Clin Cardiol 2004; 9: 235–41.
599
