Die Diagnose des Phäochromozytoms und Paraganglioms

Abstract

These results support use of the CST in combination with measurements of normetanephrine for confirming or excluding P/PGL in patients with borderline elevated test results, which should, however, first be confirmed by sampling blood under standardized resting conditions.

Improved Diagnostic Accuracy of Clonidine Suppression Testing Using an Age-Related Cutoff for Plasma Normetanephrine

“…Applying these cutoffs, the diagnostic sensitivity and specificity were as high as 96% and 100%. Similar results were reported in a second study, 16 and these thresholds are currently recommended by an international guideline. 2 One of these studies included 97 patients (48 with and 49 without PPGL), but a high proportion of the PPGL patients had markedly elevated screening NMN (in whom the diagnosis of PPGL could have been established without CST).…”

“…Our study revealed another interesting aspect. The normalization of plasma NMN at baseline sampling of the CST in more than half of the patients, which has also been observed in a smaller study, 16 suggests that repeated measurement of plasma MN and NMN with optimized preanalytics would be sufficient to exclude PPGL in a large proportion of patients. However, due to practical issues (eg, long distance to the specialized center, delayed availability of laboratory results), it can be reasonable to proceed occasionally directly to a CST.…”

“…Therefore, it is not a surprise that we found a slightly lower sensitivity when applying the previously suggested cutoffs (87.5% versus 96% and 100%). 8,16 As illustrated in Figure 1 and Table 2, sensitivity could be increased by lowering the cutoff for absolute plasma NMN levels. However, this approach simultaneously led to a reduction of specificity, which would, if generally applied, result in a relatively high number of false-positive cases and consequently to unnecessary imaging or even surgical procedures.…”

Accuracy of recommended sampling and assay methods for the determination of plasma-free and urinary fractionated metanephrines in the diagnosis of pheochromocytoma and paraganglioma: a systematic review

“…Our analysis highlights the fact, that in this setting use of for instance IA plus measurement of uMNs in 24-h urine collections as the initial diagnostic test procedure will yield a markedly higher rate of false positive results compared to blood sampling in the supine position plus measurement of pMNs with HPLC, and, even more important, the rate of false positive tests will remain considerably higher during any subsequent testing. Whether or not functional tests such as clonidine suppression [36,37] will aid in confirming the diagnosis under these circumstances is unknown. Therefore, proponents of the primary use of IA plus measurement of uMNs in 24-h urine collections for the biochemical diagnosis of P/PGL need to be aware of this potential trade–off and its continued impact on the further diagnostic process.…”

Endokrine Hypertonie

“…Bei Werten im Grenzbereich kann zur Sicherung ein Clonidinsuppressionstest durchgeführt werden, der mit einer Sensitivität von 97 % und einer Spezifität von 100 % falsch positive von richtig positiven Befunden unterscheiden kann [17]. Auch die Bestimmung von Chromogranin A kann hilfreich sein [15].…”