Is the new definition of hypertension valuable to patients?
After the publication of guidelines from the American College of Cardiology and the American Heart Association that redefined the definition of high blood pressure to be higher than 130/80 mm Hg, placing an additional 31 million American adults under the hypertension tent, the authors of this commentary stopped to ask, "What makes a disease a disease?" They point out that using a new definition of 130/80 mm Hg will now identify many people (80%) as hypertensive, but they will not need treatment. Those patients who qualify for treatment only under the new definition will be exposed to the risk of medication side effects though they are at low risk of cardiovascular disease and do not stand to benefit from treatment. Two US groups—the American College of Physicians and the American Academy of Family Physicians—have stated that they'll keep their existing definition of 140/90 mm Hg, thank you very much, consistent with most of the rest of the world. (LOE = 5)(www.essentialevidenceplus.com)
Bell KJ, Doust J, Glasziou P. Incremental benefits and harms of the 2017 American College of Cardiology/American Heart Association high blood pressure guideline. JAMA Intern Med 2018 doi:10.1001/jamainternmed.2018.0310 . [Epub ahead of print]
Study design: Other
Funding source: Self-funded or unfunded
Setting: Not applicable
What makes a disease a disease? Can mere mortals change disease definitions? To paraphrase Humpty Dumpty, a "disease" means just what we choose it to mean, neither more nor less. In 2017, two US cardiology societies decided to change the definition of hypertension, lowering the threshold to 130/80 mm Hg, largely based on the results of a single study (SPRINT) that did not measure blood pressure in the typical way. To evaluate the risk of overdiagnosis occurring as a result, the authors of this commentary used a checklist for redefining disease (JAMA Intern Med 2017;177(7):1020-1025). Here it is: (1) What is the difference between definitions? The new definition elevates the status of pre-hypertension (> 80/130 mm Hg) to hypertension and suggests drug treatment in patients at high risk. (2) How will the new definition change the prevalence of the disease? It adds 31 million more US adults to the roles and qualifies 4.2 million for treatment. (3) Why change the definition? The authors presume it's because of the results of the SPRINT trial. (4) How well does the new definition predict clinically important outcomes? Observational data suggest cardiovascular mortality doubles with every 20-mm Hg increase in systolic blood pressure, starting at 115 mm Hg. (5) How reproducible is the measurement of blood pressure? Systolic blood pressure can easily vary 10 mm Hg over repeated measures in the same person, So, not very good. (6) What are the additional benefits of including more people? It all depends on the patients' baseline risk. One estimate suggests 80% of people with newly diagnosed hypertension will not benefit (Circulation 2018;137(2):109-118). (7) What harms can come from the new definition? Fear and anxiety over having a disease; inability to get health insurance due to a pre-existing condition; risks of treatment, (8) What are the net benefits and harms to the new definition? For patients at low risk, there is no benefit to the change and some increased risk. At patients at high risk, it may be beneficial. In patients older than 80 years, those with diabetes, and those with renal disease, the benefits and risks are offsetting.
Allen F. Shaughnessy, PharmD, MMedEd
Professor of Family Medicine
How often does an elevated troponin level signify acute myocardial infarction?
Unnecessary cardiac troponin testing for patients with a low likelihood of myocardial infarction (MI) will mislead more than enlighten. Approximately 1 in 8 adults presenting to an emergency department for any reason will have an elevated serum troponin level if they are unfortunate enough to be tested, though only 1.6% will have evidence of MI. Even in patients for whom MI is suspected, troponin will be elevated without evidence of MI up to 84% of the time in the United States. Only when patients have a triad of chest pain, ischemic changes noted on cardiography, and a history of ischemic heart disease will an elevated serum troponin level consistently identify MI. (LOE = 2b)
Shah AS, Sandoval Y, Noaman A, et al. Patient selection for high sensitivity cardiac troponin testing and diagnosis of myocardial infarction: prospective cohort study. BMJ 2017;359:j4788.
Study design: Cohort (retrospective)
Funding source: Foundation
Setting: Emergency department
To conduct this study, investigators enrolled consecutive patients drawn from 3 different groups. The first group consisted of every adult presenting to a United Kingdom emergency department for any reason for whom blood was drawn (n = 1054). This blood was used to determine their cardiac troponin level. The second and third groups comprised patients presenting to all emergency departments in the United Kingdom (n = 5815) and one emergency department in the United States (n = 1631) in whom high sensitivity troponin testing was requested by the attending clinician. To determine whether an MI occurred, 2 physicians independently reviewed all clinical information, including noninvasive and invasive investigations and outcomes occurring within 30 days of presentation. In the first group of unselected patients, cardiac troponin was elevated in approximately 1 in 8 patients (13.7%), though the prevalence of MI was only 1.6%. In patients specifically selected for troponin testing (presumably because they were symptomatic), the prevalence of MI was 14.5% in the United Kingdom but only 4.2% in the United States. For these patients the positive predictive value of an elevated troponin level was 59.7% in the United Kingdom but only 16.4% in the United States. The presence of all three indicators of MI—chest pain, ischemia on electrocardiography, and a history of ischemic heart disease—dramatically increased the positive predictive value of the test. A negative troponin test result in any of the populations effectively ruled out MI (negative predictive value 100%).
POEMs are provided by Essential Evidence Plus, a point-of-care clinical decision support system published by Wiley-Blackwell. For more information, please see http://www.essentialevidenceplus.com(www.essentialevidenceplus.com).
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