The ACC/AHA guideline for cholesterol management, updated in 2013 to address statin therapy for asymptomatic adults at risk for atherosclerotic cardiovascular diseases (primary prevention), proved more accurate and efficient than the NCEP 2004 guideline at identifying which patients will benefit most from statins because of their increased risk, according to two reports published online July 14 in JAMA.
The updated ACC/AHA guideline shifted the focus of primary prevention to absolute CV risk as estimated by the 10-year ASCVD (atherosclerotic cardiovascular disease) score, rather than by cholesterol levels. Critics voiced concern that applying the new guideline in clinical practice would increase the number of adults eligible for statin therapy by several million, increasing costs and exposing many people to possible harms of statins when their benefits were still uncertain.
Two groups of researchers have now examined the accuracy and cost-effectiveness of applying the new guideline in separate studies.
In one study, investigators compared the ACC/AHA eligibility criteria for statin therapy against those of the National Cholesterol Education Program ( NCEP ), using data from a large prospective community-based asymptomatic cohort of adults aged 35 years and older participating in the Framingham Health Study. They focused on 2,425 “overwhelmingly white” men and women (mean age, 51 years) who underwent CT imaging to identify coronary artery calcium as part of the study, said Dr. Amit Pursnani of the department of radiology at Massachusetts General Hospital and Harvard Medical School, both in Boston, and his associates.
As expected, many more participants were eligible for statins according to the ACC/AHA guideline (39%), compared with the NCEP guideline (14%).
The ACC/AHA guideline was much more accurate at matching statin eligibility with the presence and extent of subclinical atherosclerosis, as measured by coronary artery calcium (CAC) scores. Patients with high-risk CAC scores were much more likely to be allocated to statin therapy using the ACC/AHA guideline (85%) than the NCEP guideline (34%).
During a mean of 9.4 years of follow-up, there were 74 incident CVD events and 43 incident coronary heart disease events. The risk of incident events among statin-eligible vs. noneligible participants was significantly higher when applying the ACC/AHA eligibility guideline, compared with the NCEP guideline. Therefore, the newer guideline was more accurate and efficient at identifying patients at highest risk.
This finding held true across several subgroups of patients, including women and patients at intermediate CVD risk according to the Framingham Risk Score. The latter subgroup is particularly important because they are “the most challenging group in clinical practice for whom to decide to initiate statin therapy,” Dr. Pursnani and his associates wrote (JAMA 2015 July 14 [ doi:10.1001/jama.2015.7515 ]).
“Extrapolating our findings to the approximately 10 million U.S. adults who are newly eligible for statins, we estimate that between 41,000 and 63,000 incident CVD events would be prevented over a 10-year period by adopting the ACC/AHA guidelines,” they said.
In the other study, Ankur Pandya, Ph.D. of the department of health policy and management, Harvard School of Public Health, Boston, and his associates constructed a microsimulation model of 1 million hypothetical U.S. adults aged 45-70 years to examine whether following the ACC/AHA guideline on statin eligibility is cost effective.
The guideline recommends statin therapy for patients who have a 7.5% or higher 10-year ASCVD risk. The model predicted that the health benefits of receiving statins at this risk threshold clearly are worth the additional costs of treating more patients, with an incremental cost-effectiveness ratio of $37,000/quality-adjusted life year (QALY) gained. This is well below the conservative $50,000/QALY threshold used in other health care cost-benefit analyses, Dr. Pandya and his associates said (JAMA 2015 July 14 [ doi:10.1001/jama.2015.6822 ]).
Moreover, the model estimated that statin therapy would still be cost effective if even more lenient ASCVD risk thresholds – 3%-4% – were used. “Shifting from the 7.5% or higher threshold to 3.0% or higher … was associated with an estimated additional 125,000-160,000 CVD events averted,” they noted.
However, these estimates were influenced by such variables as the price of the statins entered into the model (whether patients used generic or name-brand agents), patients’ level of adherence, and the risk of statin-induced diabetes, which has not yet been quantified for different groups of patients.
Dr. Pursnani’s study was supported by the National Heart, Lung, and Blood Institute’s Framingham Heart Study and the National Institutes of Health. Dr. Pursnani reported having no relevant financial disclosures; one of his associates reported ties to several imaging manufacturers. Dr. Pandya’s study was supported by the Harvard School of Public Health and the NHLBI. Dr. Pandya reported receiving grants from NIH and the AHA, and one of his associates reported receiving personal fees from OptumInsight.