EVIDENCE-BASED ANSWER
Patients with a new diagnosis of hypertension should be evaluated with a history and physical exam and the following initial studies: serum potassium and creatinine, fasting serum glucose and lipid panel, hematocrit, urinalysis, and electrocardiogram (strength of recommendation [SOR]: C, based on a consensus of expert opinion). Consensus is lacking for measuring serum sodium, calcium, and uric acid.
Testing for microalbuminuria is optional in the work-up for a patient without diabetes (SOR: C, expert consensus). Some expert panels list limited echocardiography as another option.
CLINICAL COMMENTARY
Not all recommendations for working-up hypertensive patients are cost-effective
Brian Crownover, MD, FAAFP
96th Medical Group, Family Medicine Residency, Eglin Air Force Base, Eglin, Fla
There is obvious enthusiasm among the expert panels for a detailed workup of patients with hypertension. But are the recommendations cost-effective? Annual urine dipstick testing beginning at age 30 for hypertensive patients is highly cost-effective. Identification of proteinuria and treatment with an ACE inhibitor or angiotensin receptor blocker prevents the progression of renal disease at a quality-adjusted life-year cost of $15,484 to $26,320, depending on the age group.1 Unfortunately, evaluation for secondary causes of hypertension, screening for LVH, and ruling out comorbidities have not been explicitly evaluated for cost-effectiveness.
Evidence summary
There are currently no large outcome studies evaluating the initial work-up of hypertension; however, 4 international expert panels have published recommendations.2-5 These panels advise 3 initial objectives: 1) assess lifestyle and identify other cardiovascular risk factors or concomitant disorders that may affect prognosis and guide treatment; 2) search for treatable causes of high blood pressure; and 3) assess for the presence of target organ damage that would change the management of the patient (such as chronic kidney disease or heart disease).
In addition to a thorough history and physical, the following studies are recommended for patients with newly diagnosed hypertension:
Serum potassium and creatinine. All 4 panels recommend measuring serum potassium and creatinine in order to: 1) monitor the effects of diuretics and angiotensin-converting enzyme (ACE) inhibitors used in hypertension therapy, 2) screen for unexplained hypokalemia that may indicate a low-renin form of hypertension, 3) calculate baseline creatinine clearance, and 4) screen for chronic kidney disease.
Fasting blood glucose. All 4 panels recommend measuring a fasting glucose level to screen for diabetes. An abnormal glucose level may also reveal glucose intolerance, one of the diagnostic criteria of metabolic syndrome. Up to 60% of patients with diabetes also have hypertension.6
Fasting lipid panel. All 4 expert panels recommend screening for dyslipidemia with a fasting lipid panel to assess cardiovascular risk. A cohort study evaluating 356,222 men aged 35 to 57 years found a continuous, positive, graded correlation between plasma cholesterol levels and coronary risk.7
Hematocrit. All 4 panels recommend a hematocrit to screen for anemia, which may be due to chronic kidney disease.
Urinalysis. All 4 panels recommend a urinalysis to screen for renal disease.
Electrocardiogram (ECG). All 4 panels recommend an ECG to screen for findings associated with hypertension, including left ventricular hypertrophy (LVH), myocardial infarction, and rhythm abnormalities. A cohort study followed 2363 patients for 14 years who had untreated hypertension and were without pre-existing cardiovascular disease. After controlling for age, sex, diabetes, and mean blood pressure, LVH by ECG conferred a significant increased risk for cerebrovascular events (relative risk=1.79; 95% confidence interval [CI], 1.17–2.76).8 However, in a cohort of 4684 subjects from the Framingham Heart Study, ECG had a sensitivity of only 6.9% for the detection of LVH (specificity 98.8%; positive likelihood ratio=5.3; negative likelihood ratio=0.94).8
Echocardiography. Two panels3,4 and an online text10 recommend echocardiography, preferably limited echo, as an optional study. A systematic review of studies comparing the sensitivities and specificities of ECG and echo found that each was highly specific for the detection of LVH (77%–97%), but the sensitivity of echocardiography (88%–93%) exceeded that of ECG (21%–54%). However, LVH detected by ECG is a better predictor of cardiovascular complications.11 Because echocardiography may help assess disease duration and guide management, both panels recommend it for patients with severe or refractory hypertension but without other target organ damage.