The first step to determine individual risk of clinical ASCVD is to categorize patients into 4 categories of risk, from high to low. The categories with highest overall risk (secondary prevention and primary LDL-C levels 190 mg/dL [ 4.9 mmol/L]) require prompt treatment to lower ASCVD risk without using risk calculation by the PCE, which were introduced in 2013. Adults 40 to 75 years of age with diabetes mellitus merit initiation of a moderate-intensity statin without using risk calculation by the PCE; however, it is reasonable to use PCE to fur- ther stratify risk (Section 4.3. on diabetes mellitus). The fourth category includes adults 40 to 75 years of age whose 10-year ASCVD risk is estimated by the PCE. This leads to the clinician patient risk discussion to consider the pros and cons of statin therapy; factors to consider are PCE scoring, presence or absence of other risk-en- hancing factors, potential benefit of intensified lifestyle therapy, likelihood of statin-associated side effects or drug drug interactions, and patient choice. If risk sta- tus remains uncertain after these considerations, mea- surement of CAC can provide additional information to help make a decision with regard to statin therapy. 4.4.1.2. Pooled Cohort Equations Several algorithms have been proposed for estimation A useful one, and the most representative algorithm for the United States, is one derived from 5 prospective community-based studies representing a broad spectrum of the US population Figure 2. Primary prevention. Colors correspond to Class of Recommendation in Table 2. apoB indicates apolipoprotein B; ASCVD, atherosclerotic cardiovascular disease; CAC, coronary artery calcium; HIV, human immunodeficiency virus; hsCRP, high-sensitivity C-reactive protein; LDL-C, low-density lipoprotein cholesterol; and Lp(a), lipoprotein (a). 