The captopril test and renovascular hypertension

Article Abstract:

In the renin-angiotensin system, the enzyme renin transforms the substance angiotensin to angiotensin I, which is then converted to angiotensin II by the angiotensin-converting enzyme. Angiotensin II constricts blood vessels and activates the production and release of aldosterone, an adrenal gland hormone that regulates sodium, chloride, and potassium metabolism. Captopril is an agent that prevents the action of the angiotensin-converting enzyme, and thereby prevents the production of angiotensin II and increases renin levels. Patients with renovascular hypertension, or high blood pressure associated with disorders of the kidney circulation, will have enhanced responsiveness to renin, compared with patients who have essential hypertension. The captopril test is used to screen for renovascular disease in patients with hypertension. Certain criteria were established to define an abnormal response, which is recorded one hour after 25 to 50 milligrams of captopril is given to a seated patient. Drug treatment or pre-existing kidney disease was shown to influence test results. The two studies modified either the test procedure or diagnostic criteria; their results showed that the captopril test was not as sensitive and specific as originally described (able to identify individuals who do and do not have a disease). The captopril test requires considerable attention to details of patient preparation and test performance, which may not always be possible in the routine clinical setting. Although the captopril test has various shortcomings, it can be used effectively in a selected group of patients. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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The captopril test in the detection of renovascular disease in hypertensive patients

Article Abstract:

In the renin-angiotensin system, the enzyme renin transforms the substance angiotensin to angiotensin I, which is then converted to angiotensin II by the angiotensin-converting enzyme. Angiotensin II constricts blood vessels and activates the production and release of aldosterone, an adrenal gland hormone that regulates sodium, chloride, and potassium metabolism. The drug captopril inhibits the angiotensin-converting enzyme and thereby prevents the production of angiotensin II and increases renin levels. Patients with renovascular hypertension, or high blood pressure associated with disorders of the kidney circulation, have enhanced responsiveness to renin, compared with patients who have essential hypertension. The captopril test is used to screen for renovascular disease in patients with hypertension. The value of this test for detecting renovascular disease was assessed in 149 hypertensive patients. A positive response was indicated by an increase of plasma renin activity, after an oral dose of 25 milligrams of captopril, or more than 4.44 nanograms per liter per second. The captopril test was 39 percent sensitive (identifies individuals with the disease) and 96 percent specific (identifies individuals without the disease). The test was not useful for detecting renal artery stenosis or narrowing of the blood vessel supplying the kidney. The results suggest that the captopril test is ineffective as a method of screening for renovascular hypertension. (Consumer Summary produced by Reliance Medical Information, Inc.)

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A prospective evaluation of a simplified captopril test for the detection of renovascular hypertension

Article Abstract:

In the renin-angiotensin system, the enzyme renin transforms the substance angiotensin to angiotensin I, which is then converted to angiotensin II by the angiotensin-converting enzyme. Angiotensin II constricts blood vessels and activates the production and release of aldosterone, an adrenal gland hormone that regulates sodium, chloride, and potassium metabolism. The drug captopril inhibits the angiotensin-converting enzyme and, thereby, prevents the production of angiotensin II and increases renin levels. Patients with renovascular hypertension, or high blood pressure associated with disorders of kidney circulation, have enhanced responsiveness to renin compared with patients with essential hypertension. The captopril test is used to screen for renovascular disease in patients with hypertension. Among 100 hypertensive patients, the captopril test identified 29 patients with renovascular hypertension. After administration of captopril, a plasma renin activity (PRA) of 5.7 nanograms of angiotensin per milliliter per hour or more was 100 percent sensitive and 80 percent specific for detecting renovascular hypertension (identifies individuals with and without the disease). The use of diuretics for treating hypertension reduced the specificity of the captopril test. The captopril test provides a simple, inexpensive, and well-tolerated screening method for renovascular hypertension, and has excellent sensitivity and acceptable specificity. (Consumer Summary produced by Reliance Medical Information, Inc.)

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