For this reasons, urinary metanephrines represent the test of choice
for pheochromocytoma diagnosis in pediatrics. However, it has also
been reported that the measurement of urinary metanephrines, in
particular of uNMN, by HPLC–EC, can be subjected to several analytical
interferences. This work describes interference caused by amoxicillin
on an uNMN assay commonly used in the routine clinical laboratory
practice. In case of suspected analytical interference the use of an LC–
MS/MS method as a second level test can be useful to confirm the
result. We believe that this work can be of help in distinguishing truepositive
from false-positive results in the course of a diagnosis for
pheochromocytoma.