Learn more. A new study looks at how chemicals can build up in the body through common exposures. Some alternative medicine practitioners believe that decalcifying the pineal gland can help with certain medical conditions.
Learn why this test may be necessary and the signs and…. Health Conditions Discover Plan Connect. Catecholamine Urine Test. Medically reviewed by Judith Marcin, M. Why is CATU used? They can also change in response to: outside temperature blood loss exercise low blood sugar moving from a sitting to a standing position, or vice versa Catecholamine urine testing CATU is used to diagnose certain diseases that increase catecholamine production.
What symptoms lead to ordering this test? What are the possible outcomes of this test? How do I prepare for this test? How is the test performed? Test results. Read this next. Medically reviewed by Carissa Stephens, R. Medically reviewed by Peggy Pletcher, M. Medically reviewed by Angelica Balingit, MD. Aldosterone Test. Medically reviewed by Emelia Arquilla, DO.
Medically reviewed by Alana Biggers, M. The Chemicals to Avoid in Your Shampoo and Body Wash A new study looks at how chemicals can build up in the body through common exposures. In a population study, urine specimens from normal pediatric and adult subjects, 85 hypertensive patients, and 22 patients with surgically proved pheochromocytoma were analyzed.
Most users should sign in with their email address. If you originally registered with a username please use that to sign in. To purchase short term access, please sign in to your Oxford Academic account above. Don't already have an Oxford Academic account? Oxford University Press is a department of the University of Oxford.
It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Both hereditary cases were in patients who were normotensive and asymptomatic and had no other biochemical evidence of the tumor.
Both were patients with von Hippel-Lindau syndrome and had single adrenal tumors of less than 1 cm in diameter, which were identified and removed coincidentally during surgery for renal carcinoma. The single false-negative result for plasma free metanephrines in patients with sporadic pheochromocytoma involved a patient tested for possible tumor recurrence 13 years after the removal of a large extra-adrenal pheochromocytoma.
Computed tomography and all biochemical tests yielded negative results. Since there was no evidence for a hereditary basis for the patient's disease, it was presumed that the malignancy developed secondary to remaining disease that went undetected for more than 16 years after the original tumor was removed.
Thus, despite the considerable time between biochemical testing and final diagnosis, all tests performed were designated as providing false-negative results. Integrated comparison of sensitivity and specificity using ROC curves showed that the diagnostic power of plasma free metanephrines was superior to that of all other tests Figure 1.
The areas under the ROC curves for plasma catecholamines 0. Although closer, the area under the ROC curve for urinary fractionated metanephrines 0. Areas under the ROC curves were only marginally improved when tests of urinary fractionated metanephrines were combined with those for urinary catecholamines 0.
Thus, combining tests for different analytes did not improve diagnostic efficacy beyond that of a single test of plasma free metanephrines. None of the patients without pheochromocytoma had a plasma concentration of normetanephrine above 2. Negative predictive values of tests of plasma and urinary metanephrines at different prevalences of pheochromocytoma showed that negative test results for plasma free and urinary fractionated metanephrines provided the highest probabilities for excluding pheochromocytoma at all pretest prevalences of the tumor Figure 2.
However, the posttest probability of a pheochromocytoma from a positive test result for plasma free metanephrines, although similar to that for urinary total metanephrines, was consistently higher than that from a positive test result for urinary fractionated metanephrines at all pretest prevalences of the tumor.
The present examination of biochemical tests used in the diagnosis of pheochromocytoma provides several advances over previous studies.
First, this study comprehensively compared measurements of plasma free metanephrines with all other commonly available biochemical tests used to diagnose excess catecholamine production. Second, these comparisons were made in large populations of patients with and without pheochromocytoma, who were tested for the tumor because of clinically appropriate predisposing conditions or suspicious symptoms and signs.
Finally, standard criteria that were independent of the biochemical tests being compared were used to assign patients into groups with and without the tumor. The present study confirms the findings of several other reports that measurements of plasma free metanephrines or urinary fractionated metanephrines offer higher sensitivity for diagnosis of pheochromocytoma than measurements of plasma or urinary catecholamines or of urinary total metanephrines or VMA.
Since measurements of urinary fractionated metanephrines and plasma free metanephrines offer similarly high sensitivity, a negative result for either test is equally effective for excluding pheochromocytoma. However, because urinary fractionated metanephrines have low specificity, tests of plasma free metanephrines exclude pheochromocytoma in many more patients without the tumor than do tests of urinary fractionated metanephrines.
The above considerations illustrate the importance of ROC curves for comparing different tests. At equivalent levels of sensitivity, the specificity of plasma free metanephrines is higher than that of other tests. At equivalent levels of specificity, the sensitivity of plasma free metanephrines is also higher than that of other tests, including urinary fractionated metanephrines.
To minimize the risk of missing a patient with pheochromocytoma, clinicians often use multiple biochemical tests during the initial diagnostic workup of patients with suspected tumors.
Although this may increase sensitivity, it is at the cost of decreased specificity. Thus, tests involving pairs of measurements, such as fractionated catecholamines or metanephrines, have lower specificity and higher sensitivity than tests involving single measurements, such as urinary VMA or total metanephrines Table 3. The above considerations lead us to recommend against use of multiple biochemical tests to exclude pheochromocytoma in favor of a single test of plasma free metanephrines.
In patients with negative test results for plasma free metanephrines, indiscriminate use of extra tests is unlikely to improve diagnostic efficacy. If multiple biochemical tests have been run, the decision to exclude pheochromocytoma should be based on whether plasma free metanephrines show a negative test result, regardless of whether other test results are positive or negative.
Why do plasma free metanephrines provide the best test to diagnose pheochromocytoma? First, plasma free metanephrines are produced continuously by metabolism of catecholamines within pheochromocytoma tumor cells. Second, sympathoadrenal excitation causes large increases in catecholamine release, whereas plasma free metanephrines remain relatively unaffected.
Similarly, VMA is produced mainly in the liver. The lower sensitivity and higher specificity of biochemical tests for hereditary compared with sporadic pheochromocytoma reflect different reasons for testing in the 2 groups. In contrast, sporadic pheochromocytoma is typically suspected because of signs and symptoms of catecholamine excess, produced by larger more easily detected tumors than found by routine screening in hereditary pheochromocytoma. Moreover, patients tested for sporadic pheochromocytoma who do not have the tumor are often symptomatic of some condition associated with sympathoadrenal activation, leading to relatively high numbers of false-positive results.
The consistently lower specificities of biochemical tests in patients tested for sporadic rather than for hereditary pheochromocytoma may also reflect referral of patients in the former group with previously determined positive biochemical tests.
Thus, specificities of biochemical tests for detection of sporadic pheochromocytoma in the present study are likely to be lower than in unselected populations tested by commercial laboratories, but should reflect those expected in populations tested at referral centers.
Apart from patients at risk for hereditary pheochromocytoma, patients with previously resected tumors are another at-risk group who should be tested periodically for the tumor regardless of signs and symptoms. In some patient groups, such as those with hypertension and an adrenal mass, the pretest probability of a pheochromocytoma may be higher. The probability that a negative test result excludes pheochromocytoma or that a positive test result confirms the tumor depends in part on the pretest probability of the disease.
These posttest probabilities therefore require calculation of positive and negative predictive values at different pretest probabilities prevalences of the tumor. As shown in Figure 2 , a negative test result for plasma free metanephrines or urinary fractionated metanephrines provides a high probability of excluding pheochromocytoma at all clinically relevant pretest probabilities of the tumor. A routine practice to further increase or decrease the likelihood of pheochromocytoma involves use of additional biochemical tests.
In patients with positive results for an initial test of plasma free metanephrines, extra tests can be useful, but judging the likelihood of a pheochromocytoma should first take into account results of ROC curves.
The probability of pheochromocytoma in these patients is so high that further biochemical tests to confirm the tumor may be unnecessary. In the remaining patients, in whom increased levels are insufficient to unequivocally confirm a tumor, additional judiciously selected follow-up tests are appropriate, with additional attention focused on possible causes of false-positive test results.
Because of the low prevalence of pheochromocytoma in the patient groups usually tested for the tumor, false-positive results can be expected to outnumber true-positive results for all biochemical tests, including plasma free metanephrines. There are 3 potential sources of false-positive test results: diet, drugs, and stressors. Caffeic acid, a catechol found in coffee including decaffeinated coffee , and its derivative dihydrocaffeic acid are dietary substances known to interfere with assays of plasma catecholamines.
There are many other unidentified dietary constituents that can influence the results of HPLC assays. The simplest way to avoid these sources of false-positive results is by drawing blood samples in patients who have fasted.
Acetaminophen is the only direct source of interference with assays of plasma free metanephrines that we have identified to date. In our series, treatment with tricyclic antidepressants or phenoxybenzamine dibenzyline were major causes of false-positive test results for norepinephrine and its metabolites, presumably due to presynaptic actions on sympathetic nerves. Although plasma levels of free metanephrines are less sensitive to changes in sympathoadrenal activity than are levels of the parent amines, these metabolites are nevertheless influenced by many of the same stimuli and drugs that influence plasma catecholamines.
To minimize the possibility of false-positive test results, we collected blood samples for plasma free metanephrines under the same conditions used for collection of samples for measurements of plasma catecholamines. Blood samples were drawn with patients in the supine position, through an in-dwelling intravenous catheter, and after an overnight fast. The major strength of this study—all patients were examined because of clinical suspicion of pheochromocytoma—was associated with the limitation that exclusion of pheochromocytoma required use of methods other than the biochemical tests normally used in clinical practice.
Although computed tomography and magnetic resonance imaging offer high sensitivity for detecting adrenal tumors, sensitivity decreases for detecting extra-adrenal disease. We therefore followed up patients for an average of 2. Only 1 patient in whom pheochromocytoma was initially excluded by imaging studies was subsequently found to have the disease at follow-up.
It remains possible, however, that other patients in whom pheochromocytoma was excluded according to the criteria of our study may have had undiagnosed disease. Even so and unless these numbers were large, it is unlikely that incorrect categorization of these patients would make a significant difference to the results and conclusions of the study.
A related potential limitation of the study was the need to omit from the analyses patients who did not meet the research criteria for exclusion or confirmation of pheochromocytoma. Separate analyses of how inclusion of the data from these patients would affect test performance revealed little influence on the results and conclusions of the study.
Another potential limitation of the study involved the multicenter nature of patient recruitment and subsequent measurements of urinary analytes by different laboratories compared with the single laboratory used for plasma free metanephrines. However, separate analysis of data derived from single laboratories revealed no obvious influences. Thus, rather than a limitation, the multicenter nature of the study is a strength establishing that many of the findings eg, low specificity of urinary fractionated metanephrines, low sensitivity of urinary VMA were independent of the laboratory where tests were run.
Plasma free metanephrines constitute the best test for excluding or confirming pheochromocytoma and should be the test of first choice for diagnosis of the tumor. A negative test result virtually excludes pheochromocytoma. In these patients, the immediate task is to locate the tumor.
Our website uses cookies to enhance your experience. By continuing to use our site, or clicking "Continue," you are agreeing to our Cookie Policy Continue.
Figure 1. At higher upper reference limits, rates of true-positive test results decrease ie, sensitivity decreases , whereas rates of false-positive test results increase ie, specificity increases. Figure 2. A positive or a negative result for tests of plasma or urinary metanephrines changes the respective probabilities of having or not having pheochromocytoma in relationship to different pretest probabilities prevalences of the tumor.
The dotted line represents the relationship expected between pretest and posttest probability if a test had no diagnostic value. Relationships illustrated by the filled symbols show the probabilities of having a pheochromocytoma based on positive abnormal test results, whereas the open symbols show the probabilities of not having a pheochromocytoma based on negative normal test results.
Table 1. Patient Characteristics View Large Download.
0コメント