You are a general internist seeing an ambulatory consult. This new patient is a 54-year-old male with a history of hypertension treated with calcium channel blockers. He smokes and has a sedentary lifestyle but has not had any previous cardiovascular events. What is the risk of a cardiovascular event for this patient? Recent laboratory results show normal levels of total cholesterol (198 mg/dL) and low-density lipoprotein cholesterol (138 mg/dL), but a decreased level of high-density lipoprotein cholesterol (39 mg/dL). On physical examination, his systolic and diastolic blood pressure is 130 mm Hg and 80 mm Hg, respectively. Based on this information and using an online tool (Pooled Cohort Equations [modified from the Framingham risk score, which is recommended by the American Heart Association]), you calculate his risk of a cardiovascular event (myocardial infarction, stroke, or death due to coronary artery disease) to be 12.4% at 10 years.1 Given this risk, current US, European, and Canadian guidelines recommend smoking cessation, regular physical activity, and initiation of statin therapy for primary prevention.2
When presented with the risk estimate, the patient is concerned, and although open to trying to stop smoking and exercise more, is reluctant to begin medication. Questioning the risk estimate, he points out that based on his family history of long survival without heart disease, the instrument has probably overestimated his risk. You are aware that another laboratory assay, N-terminal pro-B-type natriuretic peptide (NT-proBNP), may help to further differentiate patients at varying risk and consider whether this would help resolve the current dilemma. Before suggesting the test to the patient, you review the evidence regarding whether NT-proBNP will help to better categorize your patient's risk.
Why Clinicians Measure Prognosis
Accurate prognostic information is vitally important for patients and physicians to make optimal health-related and life decisions. For example, if a patient is at low risk of a future adverse event, the absolute benefit offered by an effective therapy may be small in relation to the potential harm, burden, and cost. Among higher-risk patients, the same treatment may offer substantial benefits. Thus, accurate prognostic assessment assists patients and physicians in the shared decision-making process, preventing testing in low-risk situations, and avoiding delays in treatment when there is a high probability of a favorable net benefit.
How Can Clinicians Estimate Prognosis?
There are several ways to estimate a patient's prognosis. First, it may sometimes be adequate for patients and clinicians to use their intuition. However, use of intuition is often limited; for example, patients with heart failure tend to overestimate their life expectancy,3 particularly if they are younger and more symptomatic. In contrast, primary care physicians overestimate mortality risk in patients with heart failure, particularly in patients who are stable and mildly symptomatic.4
Second, clinicians might consider estimates of the mean prognosis from observational studies or randomized clinical trials ...